BHARAT SANCHAR NIGAM LIMITED LIMITED DEPARTMENTAL EXAMINATION FOR TTA.

MOST EXPECTED QUESTIONS AND ANSWERS FOR 40% LDCE EXAMINATION FOR BSNL TTA TO BE HELD ON 27 - FEB- 2011

Answer all the Questions All questions carry equal Marks

Time: 3 Hrs SECTION-I MAXIMUM MARKS50

All the rough work should be done at the back side of the answer sheet.What is 3 phase current and what are its advantages?3-phase power comes in two configurations: three wire and four wire. The three wire system is called a "Delta" and was used in old manufacturing plants. It is less safe, but machines would continue to run if one phase developed a fault. Power companies will not furnish a Delta System now.

The four wire system uses a common neutral conductor and is referenced to ground, thereby is safer and much more stable.

Advantages: Three phase motors are much simpler and more reliable than single phase motors, and

you get 1.73 times the power with 1.5 times the wire.

1 In a 3 phase system, the voltages are separated byA. 45° B 90° C 120° D 180° C

2 In a delta-connected source driving a delta -connected load, the

A load voltage and line voltage are one-third the source voltage for a given phase

B. load voltage and line voltage are two-thirds the source voltage for a given phase D

C. load voltage and line voltage cancel for a given phase

D. load voltage, line voltage, and source phase voltage are all equal for a given phase D

3. In a certain three-wire Y-connected generator, the phase voltages are 2 kV. The magnitudes of the line voltages are

A 2000V B3000V C 3464V D 666V C

4. A single-phase sinusoidal voltage of 120 V is connected to a 90 load. Current in the circuit is

A. 13.3 mA B. 133 mA C. 1.33 A D. 6.2 A C

5.A three-phase generator is connected to three 90 ohms load resistors. Each coil generates 120 V ac. A common neutral line exists. How much current flows through the common neutral line?

6 In a 3 phase system when the loads are perfectly balanced, the neutral current isA maximum B 1/3 rd of Maximum C 2/3 rd of Maximum D zero D

7. The power consumption in a 3 phase Delta connection isA. More than Star connectionB. Less than Star connection C. Remain unchangedD. √3 times the Star connection

8. In a 3Phase Delta connection the line current isA.√3 times the Phase currentB. 3 times the Phase CurrentC. Both line and phase currents are similar.D. Less than the phase current as there is no 4th wire neutral.

9 A 4 wire poly phase connection is termed asA.A Delta to Star connectionB. A Star to Delta connectionC. A Delta connection with phase angle 120 degreesD. A Star connection with phase angle 120 degrees

10 The line voltage in a 4 wire star connection is 415 v. what would be its phase voltage?A. 240 V approximately.B. 215 V approximately.C. 315 V approximately.D. 400 V approximately.

11. The equation for calculation of 3 phase power supply in case of Star Delta connections.A. VL x IL x cos Φ wattsB.√3 V ph x I ph x cos Φ wattsC. both A&BD. V x I KW

12. Two inductances L1and L2 are connected in parallel. The equivalent Inductance L= A. L1 x L2 / L1 +L2 Henries

B L1 x L2 Henries

C L1 +L2 Henries

D L1 +L2 / L1 x L2 Henries

13.The impedance of a n AC series circuit is 5 ohms and the power factor is 0.8 Calculate the ResistanceA.0.4 ohmsB.1.4ohmsC 40ohmsD. 4 ohms14. A balanced load of (30+j40) ohms is connected to AC supply of 250 V Calculate the current and power factor of the circuitA. current 5A and pf is 0.6 laggingB. current 6A and pf 0.5laggingC current 6A and pf 0.6 laggingD current 60A and pf 0.8 lagging

15. The triangle formed by R, ( XL –XC), and Z is calledA. Isosceles triangleB. Load triangleC. Impedance triangleD. Sine wave triangle

16.In AC circuits, ώL represents A. impedance of the circuitB. power factor of the supplyC. Inductive reactance of the circuitD. capacitve reactance of the circuit.

17.What is the condition for Resonance in series AC circuits?A. Resonance in AC circuits occurs when both inductive and capacitive reactance are similarB Resonance in AC circuits occurs when inductive reactance is slightly more than capacitive reactanceC Resonance in AC circuits occurs when capacitive reactance is much more than inductive reactanceD. is not Equal to XC

18. Formula for calculating the series resonance in AC circuitsA ½f√LCB1/2f√LCлC1/2√LCD1/2л√LC

20 In AC RLC Circuits,At series resonance A.R=LB.C=RC.Z=RD L=Z

21 The peak voltage of a particular sine wave is measured as 340V. What would be the RMS value of the sine wave?A249.68VB.240.68VC 300VD None of the above

II DIRECT CURRENT D.C CIRCUITS APPLICATION OF OHM'S LAW. AND BASIC ELECTRONICS.

1. According to Ohm's Law the current isA) Directly proportional to applied voltage across terminalsB) Inversely proportional to applied voltage across terminals ( )C) Directly proportional to Resistance of the conductorD) Inversely proportional to applied square of the voltage across terminals

2. According to Ohm's Law the current isA) VxR B) V/I C) V/R D) None of the above ( )

3. Application of Ohm's Law isA) Independent of TemperatureB) Dependent on Temperature ( )C) Independent of Power factorD) Dependent on Power factor

• 4. What is the formula for calculating the power consumption in DC circuitsA) VxR watts B) IxR wattsC) V/Rwatts D) V/Rwatts ( )

5. The unit of measurement of a resistance isA) coulombs B) Ohms C) Amperes) D) None of the above. ( )

6. The unit of measurement of current isA) Volt B) Ohms C) Amperes D) None of the above ( )

7. The unit of measurement of potential difference across two terminals isA) Volt B) Ohms C) Amperes D) None of the above

8. When a current of 10 amps is flowing through a conductor connected across P.D of one Volt, the resistance of the conductor isA. zero ohms B. 1ohm C. 0.001ohm D. 0.1ohm ( )

9. A current of 0.5 amps is flowing through an electric Bulb whose resistance is 0.5 ohms. What is the potential drop across the filament of the bulbA 25V B2.5 Volts C 0.25 Volts D none of the above ( )

10.what is the formula to determine the power consumption in a DC circuit?A. VxI, B.V/R C. IxR D. Allthe three ( )

11.the unit of power consumption in a DC circuits isA Watts B Volts C Amperes D Ohms ( )

12 A torch bulb is rated at 2.5V.500mA . Find its resistance ?A)100 Ohms B10 Ohms C 1Ohm D.0.5 Ohms ( )

13.A resistance of 14.4 ohms is connected to a 12 V battery . Calculate the heat produced in the bulb?

A. 14.4 Watts B.12 Watts C10 Watts D. 100Watts ( )

14.When the resistances are connected in series, the total resistance is equal toA. Sum of all odd no of resistancesB. Sum of all even no of resistancesC. Sum of all the individual resistances connected end to end ( )D. Sum of first and Last resistances

15. What is the formula for calculating the Effective or Total resistance R of the circuit when four resistances R1,R2,R3,R4 are connected end to end?

A. R= R1+R2+R3-R4 ( )B. R= R4+R3+R2+R1C. R= R1+R3+R4D. None of the above

16.What is the formula for calculating the Effective or Total resistance of the circuit when four resistances R1,R2,R3,R4 are connected in Parallel?A. 1/R4 = 1/R1+1/R2+1/R3+!/R4 ( )B. 1/R = 1/R1-1/R2+1/R3-1/R4C. 1/R = 1/R1+1/R2+1/R3+1/R4D. None of the above

17. What is the formula for calculating the Effective or Total resistance of the circuit when Two resistances R1,R2, are connected in Parallel?

A. R= R1+R2 ohmsB. R= R2-R1 ohmsC. R= R1+R2/R1-R2 ohms ( )D. R= R1xR2/R1+R2 ohms

18.Two resistances of 6ohms and 3 ohms are connected in parallel, the effective resistance is

A18 OhmsB 2 OhmsC 9 Ohms ( )D 3 Ohms19 When two resistances of equal value are connected in parallel, the Total Resistance of the branch isA. Equal to double the individual resistancesB. Equal to product of the individual resistancesC. Equal to half of the individual resistanceD Equal to half of the sum of the two individual resistances.

20. Two similar bulbs whose filament resistance is 200 ohms are connected to a supply of 200 V DC. What is the current flowing through each bulb?A. 0.5 amps B 1.0 Amps C.2.0 Amps D No current flows ( )

21 What value of current would be permitted to flow through a resistance of 0.3 ohms connected across 9V battery?A 300Amps B. 30Amps C10Amps D3 Amps ( )

22. A resistor allows a current of 0.6 amps when connected to a supply of 9.6 volts. What current would flow if the same resistor is connected to 12.8 V supply? ( )A.80 amps B.0.8 amps C. 8.0 amps D. 16amps

23 Calculate the voltage supply needed to produce a current of 12 A with a 48 ohms resistor?A. 0.25 V B 4V C60 V d.576V ( )

24 calculate the voltage across 300 ohms resistor when a current of 0.004 amps flows through it/A O.012V B 0.12V C1.2 V D12V ( )

25 What current would flow when a resistor of 20 ohms connected to a 12V car battery?A. 120Amps B12Amps C 60 amps D0.6 Amps ( )

26 A 100 ohms resistor is connected to a supply of 20 V. what current would flow?A, 200Amps B 20amps. C5amps D0.2 amps ( )

27 Find the size of the resistor which would limit the current to a value of 0.002 ampswhen connected to 8V supply

A400ohms B40ohms C0.4ohms D4 ohms ( )

28 What supply voltage is needed to provide a current of 1.2 Amps through a 40 Ohms resistor?A 4.8 V B 48V C 480V D 0.48 V ( )

29 What current would flow through a resistor of 40 ohms connected to a 10V supply?A 25 Amps B 2.5 Amps C 0.25 Amps D none of the above ( )

30 The total resistance of a series combination is 500 ohms. Calculate the total current which would flow when connected to a supply of 15V supply?A 0.0003A B0.003A C 0.03 Amps D 0.3 Amps ( )

31 What value of resistor would be used to permit a flow of current 0.2 Amps connected across 6V supplyA 0.03 ohms B 0.3 ohms C3.0 Ohms D 30 Ohms ( )

31Resistivity of a wire depends on (A) length (B) material (C) cross section area (D) none of the above. ( )

32 Resistance of a wire is r ohms. The wire is stretched to double its length, then its resistance in ohms is (A) r / 2 (B) 4 r (C) 2 r (D) r / 4. ( )

33.Two bulbs marked 200 watt-250 volts and 100 watt-250 volts are joined in series to 250 volts supply. Power consumed in circuit is (A) 33 watt (B) 67 watt (C) 100 watt (D) 300 watt. ( )

34.A circuit contains two un-equal resistances in parallel

(A) current is same in both

(B) large current flows in larger resistor

(C) potential difference across each is same

(D) smaller resistance has smaller conductance. ( )

35. Conductance is expressed in terms of

(A) ohm / m (B) m / ohm (C) mho / m (D) mho. ( )

36 Two resistances R1 and R2 give combined resistance of 4.5 ohms when in series and 1 ohm when in parallel. The resistances are ( )

(A)3 ohms and 6 ohms (B)3 ohms and 9 ohms (C)1.5 ohms and 3 ohms (D)1.5 ohms and 0.5 ohms.

36 .We have three resistances of values 2 Ω, 3 Ω and 6 Ω. Which of the following combination will give an effective resistance of 4 Ω?

(A) All the three resistances in parallel

(B) 2 Ω resistance in series with parallel combination of 3 Ω and 6 Ω resistance

(C) 3 Ω resistance in series with parallel combination of 2 Ω and 6 Ω resistance ( )

(D) 6 Ω resistance in series with parallel combination of 2 Ω and 3 Ω resistance.

37.Three equal resistors connected in series across a source of emf together dissipate 10 watts of power. What would be the power dissipated in the same resistors when they are connected in parallel across the same source of emf?

(A) 10 watts (B) 30 watts (C) 90 watts (D) 270 watts. ( )

38.Four identical resistors are first connected in parallel and then in series. The resultant resistance of the first combination to the second will be

(A) 1 / 16 times (B) 1 / 4 times (C) 4 times (D) 16 times. ( )

39 .When P = Power, V = Voltage, I = Current, R = Resistance and G = Conductance, which of the following relation is incorrect?

(A) V = √ (PR) (B). P= V2G C) G= P / I2 (D) I =√ (P / R) ( )

40 .Which of the following bulbs will have the least resistance ?

(A) 220 V, 60 W (B) 220 V, 100 W (C) 115 V, 60 W (D) 115 V, 100 W. ( )

41The ratio of the resistance of a 100 W, 220 V lamp to that of a 100 W, 110 V lamp will be nearly

(A) 4 (B)2 (C) 1 / 2 (D) 1 / 4 ( )

42 The resistance of a 100 W, 200 V lamp is

(A) 100 ohm (B) 200 ohm (C) 400 ohm (D) 1600 ohm. ( )

43 Two 1 kilo ohm, 1/2 W resistors are connected in series. Their combined resistance value and wattage will be

(A) 2 kΩ, 1/2 W (B) 2 kΩ, 1 W (C) 2 kΩ, 2 W (D) l kΩ, 1/2 W. ( )

44 Which method can be used for absolute measurement of resistances ? ( )

(A)Ohm's law method (B)Wheatstone bridge method (C)Releigh method (D) Lortentz method.

45 Three 3 ohm resistors are connected to form a triangle. What is the resistance between any two of the corners?

(A) 3 / 4 ohms (B) 3 ohms (C) 2 ohms (D) 4/3 ohm. ( )

46 .Five resistances are connected as shown in figure below. The equivalent resistance between the

points A and B will be

(A) 35 ohms (B) 25 ohms (C) 15 ohms (D) 5 ohms. ( )

47 Ohm's law is not applicable to

(A) DC circuits (B) high currents (C) small resistors (D) semi-conductors ( )

48 .Ohm's law is not applicable in all the following cases Except

(A) Electrolytes (B) Arc lamps (C) Insulators (D Vacuum ratio values ( )

49 .The element of electric heater is made of

(A) copper (B) steel (C) carbon (D) nichrome. ( )

50 Variable resistors are ( )

(A)Wire wound resistors (B)Thin film resistors (C)Thick film resistors (D)All of the above.

51 A heating element of a hot plate on an electric cooking range draws 12 amperes from 240 V mains. How many kWh of energy will be consumed in one hour and 15 minutes

(A) 1.2 (B) 3.6 (C) 6.0 (D) 7.2. ( )

52.Which material is expected to have least resistivity?

(A) Copper B) Lead (C) Mercury (D) Zinc. ( )

53 The rating of fuse wire is expressed in terms of

(A) Ohms (B) Mhos (C) Amperes (D) Watts. ( )

54 Which of the following material is not used as fuse material?

(A) Silver (B) Copper (C) Aluminum (D) Carbon. ( )

55. A lamp of 100 W at 200 V is supplied current at 100 volts. It will be equivalent to the lamp of

(A) 50 W (B) 40 W (C) 25 W (D) 10 W. ( )

56. A Kilowatt/ hour is a unit ofA energy B) power C) electric charge D) current ( )

57 A 12 ohms resistance is connected across a voltage source of 12V.What is he Power dissipated in the resistor?

A12W B1/12W C1.2W D24W ( )

58.Two 12 V Car Batteries are connected in parallel. What is the terminal voltage?A. 24V B2.4V C.12V D1.2V ( )

A Ammeter B potentiometer C Volt meter D Load meter ( ) 60. The sum of two resistances is 9 ohms and their product is 18 ohms find the total resistance when they are connected in parallel A 9 ohms B18 ohms C 2 Ohms D 20 ohms

60. why do we connect a voltmeter in parallel to the load?A. Impedance is very high, hence no change in load currentB. Impedance is too low hence no change in load currentC. Impedance of the volt meter does not change the load current.D. None of the above.

61. The element Silicon is:a. a conductorb. an insulatorc. a superconductord. a semiconductor========= Answer is d =========62. An element which falls somewhere between being anInsulator and a conductor is called a:a. P-type conductorb. intrinsic conductorc. semiconductord.N-type conductor========= Answer is c =========63. In an atom:a. the protons and the neutrons orbit the nucleus in oppositeDirectionsb. the protons orbit around the neutronsc. the electrons orbit the nucleusd. the electrons and the neutrons orbit the nucleus========= Answer is c =========64. An atom that loses an electron becomes:a. a positive ionb. an isotopec. a negative iond. a radioactive atom========= Answer is a =========

65. An electric current passing through a wire will produceAround the conductor:a. an electric fieldb. a magnetic field

59.The instrument used to measure P.D across a load is called

c. an electrostatic fieldd. nothing========= Answer is b =========66. These magnetic poles repel:a. unlikeb. likec. positived. negative========= Answer is b =========67. This material is better for making a permanent magnet:a. steelb. copperc. aluminumd. soft iron========= Answer is a =========68. The better conductor of electricity is:a. copperb. carbonc. silicond. aluminum========= Answer is a =========69. The term describing opposition to electron flow in aMetallic circuit is:a. currentb. voltagec. resistanced. power========= Answer is c =========70. The substance which will most readily allow anElectric current to flow is:a. an insulatorb. a conductorc. a resistord. a dielectric========= Answer is b =========71. The plastic coating formed around wire is:a. an insulatorb. a conductorc. an inductord. a magnet========= Answer is a =========72. The following is a source of electrical energy:a. p-channel FETb. carbon resistorc. germanium dioded. lead acid battery========= Answer is d =========73. An important difference between a common torchbattery and a lead acid battery is that only the lead acidbattery:a. has two terminalsb. contains an electrolyte

c. can be re-chargedd. can be effectively discharged========= Answer is c =========74. As temperature increases, the resistance of a metallicconductor:a. increasesb. decreasesc. remains constantd. becomes negative========= Answer is a =========75. In an n-type semiconductor, the current carriers are:a. holesb. electronsc. positive ionsd.photons========= Answer is b =========76. In a p-type semiconductor, the current carriers are:a. photonsb. electronsc. positive ionsd.holes========= Answer is d =========77. An electrical insulator:a. lets electricity flow through it in one directionb. does not let electricity flow through itc. lets electricity flow through it when light shines on itd. lets electricity flow through it========= Answer is b =========78. Four good electrical insulators are:a. plastic, rubber, wood, carbonb. glass, wood, copper, porcelainc. paper, glass, air, aluminiumd. glass, air, plastic, porcelain ========= Answer is d =========79. Three good electrical conductors are:a. copper, gold, micab. gold, silver, woodc. gold, silver, aluminiumd. copper, aluminium, paper========= Answer is c =========80. The name for the flow of electrons in an electric circuit isa. voltageb. resistancec. capacitanced. current========= Answer is d ========= Measurement Units: 81 The unit of impedance is the:a. ampereb. farad

c. henryd.ohm========= Answer is d =========82. One kilohm is:a. 10 ohmb. 0.01 ohmc. 0.001 ohmd. 1000 ohm========= Answer is d =========83. One kilovolt is equal to:a. 10 voltb. 100 voltc. 1000 voltd. 10,000 volt========= Answer is c =========84. One quarter of one ampere may be written as:a. 250 microampereb. 0.5 amperec. 0.25 milliampered. 250 milliampere========= Answer is d =========85. The watt is the unit of:a. powerb. magnetic fluxc. electromagnetic field strengthd. breakdown voltage========= Answer is a =========86. The voltage 'two volt' is also:a. 2000 mVb. 2000 kVc. 2000 uVd.2000 MV========= Answer is a =========87. The unit for potential difference between two points in acircuit is the:a. ampereb. voltc. ohmd.coulomb========= Answer is b =========88. Impedance is a combination of:a. reactance with reluctanceb. resistance with conductancec. resistance with reactanced. reactance with radiation ========= Answer is c =========89. One mA is:a. one millionth of one ampereb. one thousandth of one amperec. one tenth of one ampere

d. one millionth of admittance========= Answer is b =========90. The unit of resistance is the:a. faradb. wattc. ohmd. resistor91. The voltage across a resistor carrying current can becalculated using the formula:a. E = I + R [voltage equals current plus resistance]b. E = I - R [voltage equals current minus resistance]c. E = I x R [voltage equals current times resistance]d. E = I / R [voltage equals current divided by resistance]========= Answer is c =========92. A 10 mA current is measured in a 500 ohm resistor. Thevoltage across the resistor will be:a. 5 voltb. 50 voltc. 500 voltd. 5000 volt ========= Answer is a =========93. The value of a resistor to drop 100 volt with a current of0.8 milliampere is:a. 125 ohmb. 125 kilohmc. 1250 ohmd. 1.25 kilohm ========= Answer is b =========94. I = E/R is a mathematical equation describing:a. Ohm's Lawb. Thevenin's Theoremc. Kirchoff's First Lawd. Kirchoff's Second Law========= Answer is a =========95. The voltage to cause a current of 4.4 ampere in a 50 ohm resistance is:a. 2220 voltb. 220 voltc. 22.0 voltd. 0.222 volt========= Answer is b =========96. A current of 2 ampere flows through a 16 ohm resistance.The applied voltage is:a. 8 voltb. 14 voltc. 18 voltd. 32 volt========= Answer is d =========97. A current of 5 ampere in a 50 ohm resistance produces apotential difference of:a. 20 voltb. 45 volt

c. 55 voltd. 250 volt========= Answer is d =========98. This voltage is needed to cause a current of 200 mA toflow in a lamp of 25 ohm resistance:a. 5 voltb. 8 voltc. 175 voltd. 225 volt========= Answer is a =========99. A current of 0.5 ampere flows through a resistance when6 volt is applied. To change the current to 0.25 amperethe voltage must be:a. increased to 12 voltb. reduced to 3 voltc. held constantd. reduced to zero========= Answer is b =========100 The current flowing through a resistor can becalculated by using the formula:a. I = E x R [current equals voltage times resistance]b. I = E / R [current equals voltage divided by resistance]c. I = E + R [current equals voltage plus resistance]d. I = E - R [current equals voltage minus resistance]========= Answer is b =========101. When an 8 ohm resistor is connected across a 12 voltsupply the current flow is:a. 12 / 8 ampsb. 8 / 12 ampsc. 12 - 8 ampsd. 12 + 8 amps========= Answer is a =========102. A circuit has a total resistance of 100 ohm and 50 voltis applied across it. The current flow will be:a. 50 mAb.500 mAc. 2 ampered. 20 ampere========= Answer is b =========103. The following formula gives the resistance of a circuit:a. R = I / E [resistance equals current divided by voltage]b. R = E x I [resistance equals voltage times currentc. R = E / R [resistance equals voltage divided byresistance]d. R = E / I [resistance equals voltage divided by current]========= Answer is d =========104. A resistor with 10 volt applied across it and passing acurrent of 1 mA has a value of:a. 10 ohmb. 100 ohm

c. 1 kilohmd. 10 kilohm========= Answer is d =========105. If a 3 volt battery causes 300 mA to flow in a circuit,the circuit resistance is:a. 10 ohmb. 9 ohmc. 5 ohmd. 3 ohm========= Answer is a =========106. A current of 0.5 ampere flows through a resistor when12 volt is applied. The value of the resistor is:a. 6 ohmsb. 12.5 ohmsc. 17 ohmsd. 24 ohms========= Answer is d =========107. The resistor which gives the greatest opposition tocurrent flow is:a. 230 ohmb. 1.2 kilohmc. 1600 ohmd. 0.5 megohm========= Answer is d =========108. The ohm is the unit of:a. supply voltageb. electrical pressurec. current flowd. electrical resistance========= Answer is d =========109. If a 12 volt battery supplies 0.15 ampere to a circuit,the circuit's resistance is:a. 0.15 ohmb. 1.8 ohmc. 12 ohmd. 80 ohm========= Answer is d =========110. If a 4800 ohm resistor is connected to a 12 volt battery,the current flow is:a. 2.5 mAb.25 mAc. 40 Ad. 400 A========= Answer is a =========

111. The total resistance in a parallel circuit:a. is always less than the smallest resistanceb. depends upon the voltage drop across each branchc. could be equal to the resistance of one branch

d. depends upon the applied voltage========= Answer is a =========112. Two resistors are connected in parallel and are connectedacross a 40 volt battery. If each resistor is 1000 ohms, thetotal battery current is:a. 40 ampereb. 40 milliamperec. 80 ampered. 80 milliampere========= Answer is d =========113. The total current in a parallel circuit is equal to the:a. current in any one of the parallel branchesb. sum of the currents through all the parallel branchesc. applied voltage divided by the value of one of theresistive elementsd. source voltage divided by the sum of the resistiveelements========= Answer is b =========114. One way to operate a 3 volt bulb from a 9 volt supply isto connect it in:a. series with the supplyb. parallel with the supplyc. series with a resistord. parallel with a resistor========= Answer is c =========115. You can operate this number of identical lamps, each drawing a current of 250 mA, from a 5A supply:a. 50b.30c. 20d.5========= Answer is c =========116. Six identical 2-volt bulbs are connected in series. Thesupply voltage to cause the bulbs to light normally is:a. 12 Vb. 1.2 Vc. 6 Vd. 2 V========= Answer is a =========117. This many 12 volt bulbs can be arranged in series to forma string of lights to operate from a 240 volt power supply:a. 12 x 240b. 240 + 12c. 240 - 12d. 240 / 12========= Answer is d =========118. Three 10,000 ohm resistors are connected in series acrossa 90 volt supply. The voltage drop across one of theresis tors is:a. 30 voltb. 60 volt

c. 90 voltd. 15.8 volt========= Answer is a =========119. Two resistors are connected in parallel. R1 is 75 ohm and R2 is 50 ohm. The total resistance of this parallel circuit is:a. 10 ohmb. 70 ohmc. 30 ohmd. 40 ohm========= Answer is c =========120. A dry cell has an open circuit voltage of 1.5 volt. When supplying a large current the voltage drops to 1.2 volt. This is due to the cell's:a. internal resistanceb. voltage capacityc. electrolyte becoming dryd. current capacity========= Answer is a =========121. A 6 ohm resistor is connected in parallel with a 30 ohm resistor. The total resistance of the combination is:a. 5 ohmb. 8 ohmc. 24 ohmd. 35 ohm========= Answer is a =========122. The total resistance of several resistors connected inseries is:a. less than the resistance of any one resistorb. greater than the resistance of any one resistorc. equal to the highest resistance presentd. equal to the lowest resistance present========= Answer is b =========123. Five 10 ohm resistors connected in series give a totalresistance of:a. 1 ohmb. 5 ohmsc. 10 ohmsd. 50 ohms========= Answer is d =========124. Resistors of 10, 270, 3900, and 100 ohm are connectedin series. The total resistance is:a. 9 ohmb. 3900 ohmc. 4280 ohmd. 10 ohm========= Answer is c =========125. This combination of series resistors could replace asingle 120 ohm resistor:a. five 24 ohmb. six 22 ohm

c. two 62 ohmd. five 100 ohm========= Answer is a =========126. If a 2.2 megohm and a 100 kilohm resistor areconnected in series, the total resistance is:a. 2.1 megohmb. 2.11 megohmc. 2.21 megohmd. 2.3 megohm========= Answer is d =========127. If ten resistors of equal value R are wired in parallel,the total resistance is:a. Rb.10Rc. 10/Rd.R/10========= Answer is d =========128. The total resistance of four 68 ohm resistors wired inparallel is:a. 12 ohmb. 17 ohmc. 34 ohmd. 272 ohm========= Answer is b =========129. Resistors of 68 ohm, 47 kilohm, 560 ohm and 10 ohmare connected in parallel. The total resistance is:a. less than 10 ohmb. between 68 and 560 ohmc. between 560 and and 47 kilohmd. greater than 47 kilohm========= Answer is a =========130. The following resistor combination can most nearlyreplace a single 150 ohm resistor:a. four 47 ohm resistors in parallelb. five 33 ohm resistors in parallelc. three 47 ohm resistors in seriesd. five 33 ohm resistors in series========= Answer is c =========131. Two 120 ohm resistors are arranged in parallel toreplace a faulty resistor. The faulty resistor had anoriginal value of:a. 15 ohmb. 30 ohmc. 60 ohmd. 120 ohm ========= Answer is c =========132. Two resistors are in parallel. Resistor A carries twicethe current of resistor B which means that:a. A has half the resistance of Bb. B has half the resistance of A

c. the voltage across A is twice that across Bd. the voltage across B is twice that across B========= Answer is a =========133. The smallest resistance that can be made with five 1 k ohm resistors is:a. 50 ohm by arranging them in seriesb. 50 ohm by arranging them in parallelc. 200 ohm by arranging them in seriesd. 200 ohm by arranging them in para llel ========= Answer is d =========134. The following combination of 28 ohm resistors has a total resistance of 42 ohm:a. three resistors in seriesb. three resistors in parallelc. a combination of two resistors in parallel, then placed inseries with another resistord. a combination of two resistors in parallel, then placed inseries with another two in parallel ========= Answer is c =========135. Two 100 ohm resistors connected in parallel are wiredin series with a 10 ohm resistor. The total resistance ofthe combination is:a. 60 ohmsb. 180 ohmsc. 190 ohmsd. 210 ohms ========= Answer is a =========136. A 5 ohm and a 10 ohm resistor are wired in series andconnected to a 15 volt power supply. The current flowingfrom the power supply is:a. 0.5 ampereb. 1 amperec. 2 ampered. 15 ampere========= Answer is b =========137. Three 12 ohm resistors are wired in parallel and connected to an 8 volt supply. The total current flowfrom the supply is:a. 1 ampereb. 2 amperesc. 3 amperesd. 4.5 amperes========= Answer is b =========138. Two 33 ohm resistors are connected in series with apower supply. If the current flowing is 100 mA, thevoltage across one of the resistors is:a. 66 voltb. 33 voltc. 3.3 voltd. 1 volt========= Answer is c =========139. A simple transmitter requires a 50 ohm dummy load.You can fabricate this from:a. four 300 ohm resistors in parallelb. five 300 ohm resistors in parallel

c. six 300 ohm resistors in paralleld. seven 300 ohm resistors in parallel========= Answer is c =========140. Three 500 ohm resistors are wired in series. Short circuitingthe centre resistor will change the value of the network from:a. 1500 ohm to 1000 ohmb. 500 ohm to 1000 ohmc. 1000 ohm to 500 ohmd. 1000 ohm to 1500 ohm========= Answer is a ========= Power calculations141. A transmitter power amplifier requires 30 mA at 300 volt. The DC input power is:a. 300 wattb. 9000 wattc. 9 wattd. 6 watt========= Answer is c =========142. The DC input power of a transmitter operating at 12 volt and drawing 500 milliamp would be:a. 6 wattb. 12 wattc. 20 wattd. 500 watt========= Answer is a =========143. When two 500 ohm 1 watt resistors are connected inseries, the maximum total power that can be dissipated byboth resistors is:a. 4 wattb. 2 wattc. 1 wattd. 1/2 watt========= Answer is b =========144. When two 1000 ohm 5 watt resistors are connected inParallel, they can dissipate a maximum total power of:a. 40 wattb. 20 wattc. 10 wattd. 5 watt========= Answer is c =========145. The current in a 100 kilohm resistor is 10 mA. The powerDissipated is:a. 1 wattb. 10 wattc. 100 wattd. 10,000 watt========= Answer is b =========

146. A current of 500 milliamp passes through a 1000 ohmresistance. The power dissipated is:a. 0.25 wattb. 2.5 watt

c. 25 wattd. 250 watt========= Answer is d =========147. A 20 ohm resistor carries a current of 0.25 ampere. Thepower dissipated is:a. 1.25 wattb. 5 wattc. 2.50 wattd. 10 watt========= Answer is a =========148. If 200 volt is applied to a 2000 ohm resistor, the resistorwill dissipate:a. 20 wattb. 30 wattc. 10 wattd. 40 watt========= Answer is a =========149. The power delivered to an antenna is 500 watt. Theeffective antenna resistance is 20 ohm. The antennacurrent is:a. 25 ampb. 2.5 ampc. 10 ampd. 5 amp========= Answer is d =========150. The unit for power is the:a. ohmb.wattc. ampered. volt========= Answer is b =========151. The following two quantities should be multipliedtogether to find power:a. resistance and capacitanceb. voltage and currentc. voltage and inductanced. inductance and capacitance========= Answer is b =========152. The following two electrical units multiplied togethergive the unit "watt":a. volt and ampereb. volt and faradc. farad and henryd. ampere and henry========= Answer is a =========153. The power dissipation of a resistor carrying a currentof 10 mA with 10 volt across it is:a. 0.01 wattb. 0.1 watt

c. 1 wattd. 10 watt========= Answer is b =========154. If two 10 ohm resistors are connected in series with a10 volt battery, the battery load is:a. 5 wattb. 10 wattc. 20 wattd. 100 watt========= Answer is a =========155. Each of 9 resistors in a circuit is dissipating 4 watt. Ifthe circuit operates from a 12 volt supply, the totalcurrent flowing in the circuit is:a. 48 ampereb. 36 amperec. 9 ampered. 3 ampere========= Answer is d =========156. Three 18 ohm resistors are connected in parallel acrossa 12 volt supply. The total power dissipation of the resistor load is:a. 3 wattb. 18 wattc. 24 wattd. 36 watt========= Answer is c =========157. A resistor of 10 kilohm carries a current of 20 mA. Thepower dissipated in the resistor is:a. 2 wattb. 4 wattc. 20 wattd. 40 watt========= Answer is b =========158. A resistor in a circuit becomes very hot and starts toburn. This is because the resistor is dissipating too much:a. currentb. voltagec. resistanced.power========= Answer is d =========159. A current of 10 ampere rms at a frequency of 50 Hzflows through a 100 ohm resistor. The power dissipated is:a. 500 wattb. 707 wattc. 10,000 wattd. 50,000 watt========= Answer is c =========160. The voltage applied to two resistors in series isdoubled. The total power dissipated will:a. increase by four timesb. decrease to half

c. doubled. not change========= Answer is a ========= Alternating current: 161. An 'alternating current' is so called because:a. it reverses direction periodicallyb. it travels through a circuit using alternate pathsc. its direction of travel is uncertaind. its direction of travel can be altered by a switch========= Answer is a =========162. The time for one cycle of a 100 Hz signal is:a. 1 secondb. 0.01 secondc. 0.0001 secondd. 10 seconds========= Answer is b =========163. A 50 hertz current in a wire means that:a. a potential difference of 50 volts exists across the wireb. the current flowing in the wire is 50 amperesc. the power dissipated in the wire is 50 wattsd. a cycle is completed 50 times in each second========= Answer is d =========164. The current in an AC circuit completes a cycle in 0.1second. So the frequency is:a. 1 Hzb. 10 Hzc. 100 Hzd. 1000 Hz========= Answer is b =========

165. An impure signal is found to have 2 kHz and 4 kHzcomponents. This 4 kHz signal is:a. a fundamental of the 2 kHz signalb. a sub-harmonic of 2 kHzc. the DC component of the main signald. a harmonic of the 2 kHz signal========= Answer is d =========166. The correct name for the equivalent of 'one cycle persecond' is one:a. henryb. voltc. hertzd.coulomb========= Answer is c =========

167. One megahertz is equal to:a. 0.0001 Hzb. 100 kHzc. 1000 kHz

d. 10 Hz========= Answer is c =========168. One GHz is equal to:a. 1000 kHzb. 10 MHzc. 100 MHzd.1000 MHz========= Answer is d =========169. The 'rms value' of a sine-wave signal is:a. half the peak voltageb. 1.414 times the peak voltagec. the peak-to-peak voltaged. 0.707 times the peak voltage========= Answer is d =========170. A sine-wave alternating current of 10 ampere peak hasan rms value of:a. 5 ampb. 7.07 ampc. 14.14 ampd. 20 amp========= Answer is b ========= Capacitors, Inductors,Resonance: 171. The total capacitance of two or more capacitors in seriesis:a. always less than that of the smallest capacitorb. always greater than that of the largest capacitorc. found by adding each of the capacitances togetherd. found by adding the capacitances together and dividingby their total number========= Answer is a =========172. Filter capacitors in power supplies are sometimesconnected in series to:a. withstand a greater voltage than a single capacitor canwithstandb. increase the total capacityc. reduce the ripple voltage furtherd. resonate the filter circuit========= Answer is a =========173. A radio component is identified as a capacitor if its valueis measured in:a. microvoltsb. millihenrysc. megohmsd. microfarads ========= Answer is d =========174. Two metal plates separated by air form a 0.001 uFcapacitor. Its value may be changed to 0.002 uF by:a. bringing the metal plates closer togetherb. making the plates smaller in size

c. moving the plates apartd. touching the two plates together========= Answer is a =========175. The material separating the plates of a capacitor is the:a. dielectricb. semiconductorc. resistord. lamination========= Answer is a =========176. Three 15 picofarad capacitors are wired in parallel. Thevalue of the combination is:a. 45 picofaradb. 18 picofaradc. 12 picofaradd. 5 picofarad========= Answer is a =========177. Capacitors and inductors oppose an alternating current.This is known as:a. resis tanceb. resonancec. conductanced. reactance========= Answer is d =========178. The reactance of a capacitor increases as the:a. frequency increasesb. frequency decreasesc. applied voltage increasesd. applied voltage decreases========= Answer is b =========

179. The reactance of an inductor increases as the:a. frequency increasesb. frequency decreasesc. applied voltage increasesd. applied voltage decreases========= Answer is a =========180. Increasing the number of turns on an inductor willmake its inductance:a. decreaseb. increasec. remain unchangedd. become resistive========= Answer is b =========

181. The unit of inductance is the:a. faradb.henryc. ohm

d. reactance========= Answer is b =========182. Two 20 uH inductances are connected in series. Thetotal inductance is:a. 10 uHb. 20 uHc. 40 uHd. 80 uH========= Answer is c =========183. Two 20 uH inductances are connected in parallel. Thetotal inductance is:a. 10 uHb. 20 uHc. 40 uHd. 80 uH========= Answer is a =========184. A toroidal inductor is one in which the:a. windings are wound on a closed ring of magneticmaterialb. windings are air-spacedc. windings are wound on a ferrite rodd. inductor is enclosed in a magnetic shield========= Answer is a =========185. A transformer with 100 turns on the primary windingand 10 turns on the secondary winding is connected to230 volt AC mains. The voltage across the secondary is:a. 10 voltb. 23 voltc. 110 voltd. 2300 volt========= Answer is b =========

186. An inductor and a capacitor are connected in series. Atthe resonant frequency the resulting impedance is :a. maximumb.minimumc. totally reactived. totally inductive========= Answer is b =========187. An inductor and a capacitor are connected in parallel.At the resonant frequency the resulting impedance is:a. maximumb. minimumc. totally reactived. totally inductive ========= Answer is a =========188. An inductor and a capacitor form a resonant circuit.The capacitor value is increased by four times. Theresonant frequency will:a. increase by four times

b. doublec. decrease to halfd. decrease to one quarter========= Answer is c =========189. An inductor and a capacitor form a resonant circuit. Ifthe value of the inductor is decreased by a factor of four,the resonant frequency will:a. increase by a factor of fourb. increase by a factor of twoc. decrease by a factor of twod. decrease by a factor of four========= Answer is b =========190. A "high Q" resonant circuit is one which:a. carries a high quiescent currentb. is highly selectivec. has a wide bandwidthd. uses a high value inductance========= Answer is b =========191wires carrying high voltages in a transmitter should bewell insulated to avoid:a. short circuitsb. overheatingc. over modulationd. SWR effects========= Answer is a =========. Semiconductors: 191. The basic semiconductor amplifying device is a:a. diodeb. transistorc. pn-junctiond. silicon gate ========= Answer is b =========192. Zener diodes are normally used as:a. RF detectorsb. AF detectorsc. current regulatorsd. voltage regulators========= Answer is d =========193. The voltage drop across a germanium signal diode whenConducting is about:a. 0.3Vb.0.6Vc. 0.7Vd.1.3V========= Answer is a =========

194. A bipolar transistor has three terminals named:a. base, emitter and drainb. collector, base and sourcec. emitter, base and collector

d. drain, source and gate========= Answer is c =========195. The three leads from a PNP transistor are named the:a. collector, source, drainb. gate, source, drainc. drain, base, sourced. collector, emitter, base========= Answer is d =========196. A low-level signal is applied to a transistor circuit inputand a higher-level signal is present at the output. Thiseffect is known as:a. amplificationb. detectionc. modulationd. rectification========= Answer is a =========197. The type of rectifier diode in almost exclusive use inpower supplies is:a. lithiumb. germaniumc. silicond. copper-oxide========= Answer is c =========198. One important application for diodes is recoveringinformation from transmitted signals. This is referred toas:a. biasingb. rejuvenationc. ionisationd. demodulation========= Answer is d =========199. In a forward biased pn junction, the electrons:a. flow from p to nb. flow from n to pc. remain in the n regiond. remain in the p region========= Answer is b =========200. The following material is considered to be asemiconductor:a. copperb. sulphurc. silicond. tantalum========= Answer is c =========

201. A varactor diode acts like a variable:a. resistanceb. voltage regulatorc. capacitance

d. inductance========= Answer is c =========202. A semiconductor is said to be doped when smallquantities of the following are added:a. electronsb. protonsc. ionsd. impurities========= Answer is d =========203. The connections to a semiconductor diode are knownas:a. cathode and drainb. anode and cathodec. gate and sourced. collector and base========= Answer is b =========204. Bipolar transistors usually have:a. 4 connecting leadsb. 3 connecting leadsc. 2 connecting leadsd. 1 connecting lead========= Answer is b =========205. A semiconductor is described as a "general purposeaudio NPN device". This is a:a. triodeb. silicon diodec. bipolar transistord. field effect transistor========= Answer is c =========206. Two basic types of bipolar transistors are:a. p-channel and n-channel typesb. NPN and PNP typesc. diode and triode typesd. varicap and zener types ========= Answer is b =========207. A transistor can be destroyed in a circuit by:a. excessive lightb. excessive heatc. saturationd. cut-off ========= Answer is b =========208. To bias a transistor to cut-off, the base must be:a. at the collector potentialb. at the emitter potentialc. mid-way between collector and emitter potentialsd. mid-way between the collector and the supply potentials========= Answer is b =========209. Two basic types of field effect transistors are:a. n-channel and p-channelb.NPN and PNPc. germanium and silicon

d. inductive and capacitive========= Answer is a =========210. A semiconductor with leads labelled gate, drain andsource, is best described as a:a. bipolar transistorb. silicon diodec. gated transistord. field-effect transistor========= Answer is d ========= Meters and Measuring: 211. An ohmmeter measures the:a. value of any resistance placed between its terminalsb. impedance of any component placed between itsterminalsc. power factor of any inductor or capacitor placed betweenits terminalsd. voltage across any resistance placed between itsterminals========= Answer is a =========212. A VSWR meter switched to the "reverse" positionprovides an indication of:a. power output in wattsb. relative reflected voltagec. relative forward voltaged. reflected power in dB========= Answer is b =========213. The correct instrument for measuring the supply currentto an amplifier is a:a. wattmeterb. voltmeterc. ammeterd.ohmmeter========= Answer is c =========214. The following meter could be used to measure the power supply current drawn by a small hand-held transistorised receiver:a. a power meterb. an RF ammeterc. a DC ammeterd. an electrostatic voltmeter ========= Answer is c =========215. When measuring the current drawn by a light bulb from aDC supply, the meter will act in circuit as:a. an insulatorb. a low value resistancec. a perfect conductord. an extra current drain ========= Answer is b =========216. When measuring the current drawn by a receiver from apower supply, the current meter should be placed:a. in parallel with both receiver power supply leadsb. in parallel with one of the receiver power leads

c. in series with both receiver power leadsd. in series with one of the receiver power leads========= Answer is d =========217. An ammeter should not be connected directly across theterminals of a 12 volt car battery because:a. the resulting high current will probably destroy theammeterb. no current will flow because no other components are inthe circuitc. the battery voltage will be too low for a measurablecurrent to flowd. the battery voltage will be too high for a measurablecurrent to flow========= Answer is a =========218. A good ammeter should have:a. a very high internal resistanceb. a resistance equal to that of all other components in thecircuitc. a very low internal resistanced. an infinite resistance========= Answer is c =========219. A good voltmeter should have:a. a very high internal resistanceb. a resistance equal to that of all other components in thecircuitc. a very low internal resistanced. an inductive reactance========= Answer is a =========220. An rms -reading voltmeter is used to measure a 50 Hzsinewave of known peak voltage 14 volt. The meterreading will be about:a. 14 voltb. 28 voltc. 10 voltd. 50 volt========= Answer is c ========= 221. Two amplifiers with gains of 10 dB and 40 dB areconnected in cascade. The gain of the combination is:a. 8 dBb. 30 dBc. 50 dBd. 400 dB========= Answer is c =========

222 An amplifier with a gain of 20 dB has a -10 dB attenuatorconnected in cascade. The gain of the combination is:a. 8 dBb. 10 dB

c. -10 dBd. -200 dB========= Answer is b =========223. Each stage of a three-stage amplifier provides 5 dB gain. The total amplification is:a. 10 dBb. 15 dBc. 25 dBd. 125 dB224. The following unit in a DC power supply performs arectifying operation:a. an electrolytic capacitorb. a fusec. a crowbard. a full-wave diode bridge========= Answer is d =========225. The following unit in a DC power supply performs asmoothing operation:a. an electrolytic capacitorb. a fusec. a crowbara full-wave diode bridge

d. ========= Answer is a =========

226 The block marked 'Rectifier' in the diagram is to:

a. turn the AC voltage from the transformer into a fluctuating DC voltageb. rectify any waveform errors introduced by the transformerc. turn the sinewave output of the rectifier into a square waved. remove any AC components from the output of the transformer========= Answer is a =========

COMMUNICATIONS NET WOKS.

Filters

226 In communication net work Filters are

A. Passive networks B. Active Networks C. Passive only in lower frequenciesD. Active only in Higher frequencies. Ans: A 227. The cut off frequency in case Filters isA. The frequency that passes through the filterB. The frequency that is rejected by the filter

C. The frequency that separates pass band and attenuation band CD. The frequency at which the filter works

228. If a filter allows all the frequencies above the cut off frequency without attenuation, the filter isA. Band Pass FilterB. High pass Filter BC Band Elimination FilterD A simple Low Pass Filter.

229. If a filter allows all the frequencies below the cut off frequency without attenuation, the filter isA. Band Pass FilterB. High pass Filter DC Band Elimination FilterD A simple Low Pass Filter.

230 If a filter allows all the frequencies with in the range of cut off frequencies without attenuation, the filter isA. Band Pass FilterB. High pass Filter AC Band Elimination FilterD A simple Low Pass Filter.

231 If a filter allows all the frequencies other than the range of cut off frequencies without attenuation, the filter isA. Band Pass FilterB. High pass Filter CC Band Elimination FilterD A simple Low Pass Filter.

Amplitude modulation is a type of modulation where the amplitude of the carrier signal is varied in accordance with the information bearing signal.

Used in Radio communication and broadcasting. Advantages of Amplitude Modulation, AMThere are several advantages of amplitude modulation, and some of these reasons have meant that it is still in widespread use today:

DI. It is simple to implement

DII. it can be demodulated using a circuit consisting of very few components

DIII. AM receivers are very cheap as no specialized components are needed.

Disadvantage of AM

It is not efficient in terms of its power usage

D. It is not efficient in terms of its use of bandwidth, requiring a bandwidth equal to twice that of the highest audio frequency

DI. It is prone to high levels of noise because most noise is amplitude based and obviously AM detectors are sensitive to it.

FREQUENCY MODULATION:Frequency modulation is a type of modulation where the frequency of the carrier is varied in accordance with the modulating signal. The amplitude of the carrier remains constant. FM modulation is a low-noise process and provides a high quality modulation technique which is used for music and speech in hi-fidelity broadcasts.

ADVANTAGES: 1 Resilience to noise:

2.Easy to apply modulation at a low power stage of the transmitter

3. It is possible to use efficient RF amplifiers with frequency modulated signals:

PULSE CODE MODULATION: Pulse code modulation (PCM) is a digital scheme for transmitting analog data. The signals in PCM are binary; that is, there are only two possible states, represented by logic 1 (high) and logic0 (low).