Capacitors+Dc Circuits

7/30/2019 Capacitors+Dc Circuits

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1.Null point in the galvanometer is obtained when a cell ofemf Eand internal resistance ris connected across the length of a 22 cm wire of

the potentiometer. Now a resistance of is connected across the terminals of the cell (by closing the key K) and null point is obtainedagainst the length of 20 cm. Then the internal resistance rof the cell is.

2. Each sidesAB, BC, AC, DE, EF, and FD (where D, Eand Fare mid points ofBC, ACandAB respectively) has resistance .Find the equivalent resistance between B and Cin ohms.

Explanation:

3. The amount of charge that flows through the switch after closing it is . Findx.

Explanation:

4. In the circuit shown in figure, find the steady state charge on the capacitor in .


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Explanation:

5.

Two electric bulbs A and B are designed for the same voltage. Their power ratings are PA and PB respectively, with PA > PB. If they are joinedin series across a V-volt supply,

[A] A will draw more power than B[B] B will draw more power than A Correct[C] The ratio of powers drawn by them will depend on V[D] A and B will draw the same power

6. B is a 1.5 V, 0.30 A, 5.0 torch bulb working properly in the circuit shown. The combined resistance of R and B, between the points X andY, is :

17.

The circuit shown in figure is used to compare the emf's of two cells and . The null point is at C when the galvanometer is

connected to . When the galvanometer is connected to , the null point will be

[A] to the left of C C[B] to the right of C

[C] at C itself[D] nowhere on AB

8. The current passing through the ideal ammeter in the circuit given below is :

1

9.A potentiometer wire of length 10 m and resistance is connected in series with a 15 Vbattery and an external resistance . Asecondary cell ofemf Ein the secondary circuit is balanced by 240 cm long potentiometer wire. The emf Eof the cell is :


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Explanation:

10. In the given network, the value ofC, so that an equivalent capacitance betweenA and B is , is :

Explanation:

11. In the circuit shown in the figure, the current I has a value equal to :

112. The equivalent resistance between A and B in the network in the figure is :

4/313. The length of a wire of a potentiometer is 100 cm, and the e.m.f. of its standard cell is E volt. It is employed to measure the e.m.f. of a

battery whose internal resistance is . If the balance point is obtained at from the positive end, the e.m.f. of the battery is :Null points is independent of internal resistance of unknown Battery.

So,


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14. Two cells of e.m.f.s E1 and E2 (E1 > E2) are connected as shown.

When a potentiometer is connected between A and B, the balancing length of the potentiometer wire is 300 cm. On connecting same

potentiometer between A and C, the balancing length is 100 cm. The ratio is :Explanation:

15.

In the network shown, points A, B and C are at potentials of 70V, zero, and 10V, respectively :

[A] Point D is at a potential of 40V c[B] The currents in the sections, AD, DB, DC are in the ratio 3 : 2 : 1 c[C] The currents in the sections AD, DB, DC are in the ratio 1 : 2 : 3[D] The network draws a total power of 200W c

16.

A galvanometer has a resistance of and a full scale deflection current . It can be used as a voltmeter or as a higher rangeammeter provided that a resistance is added to it. Which of the following is(are) true ?

[A] 10 V range with approximately resistance in series c

[B] 30 V range with approximately resistance in series

[C] 1 mA range with resistance in parallel

[D] 0.1 mA range with resistance in parallel c

17. Four conducting parallel plates each of areaA are placed as shown and each separation is d. Plates Mand Nare connected with aconducting wire and platesXand Yare connected by a cell ofemf Vvolts with positive terminal towardsX. Find the charge appearing on thelower surface ofY.

Explanation:


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And

18.In the adjacent figure, the two capacitors each of equal capacitance Chave charges CE/2 and CEas shown initially.

As soon as the switch is closed, the current in resistance Ris.

[A]

[B]

[C]

[D]

Heat dissipated in the circuit after closing the switch is.

[A]

[B]

[C]

[D]

Final steady state

final charges on left and right capacitorsAre 5CE / 4 and CE / 4 respectively

heat =

heat =

=

20. The current through resistance is zero and through is 2A.


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The value ofRis :

As and are in parallel so to current through is also zero. Wheatstone network is balanced.

21. The current through resistance is zero and through is 2A.

The emf Eof the ideal cell is : 1022.

Given that potential difference across capacitor is 10 V. Then.

[A] potential difference across capacitor is 40 V

[B] potential difference across capacitor is 2.5 V c

[C] potential difference across capacitor is 5 V[D] value ofEis 70 V

23. The capacitorChas an initial charge CE. At time t= 0, the switch S is closed. The adjacent figure shows the instantaneous charge q inthe capacitor 2Cat time t. The variation ofq with time is best represented by :


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24.

In the network shown all the ammeters are ideal. The ammeter which gives the maximum reading is :

[A] A1[B] A2[C] A3[D] A4

xplanation:

25. The switch is closed at t= 0. Initially capacitor is uncharged. The power given to the capacitorCat time t= RCis:

Explanation:

& .

Power =

26. Two capacitors with charges Q0 and 3 Q0 are connected through a resistance Ras shown. The charge that flows in the circuit tillstabilization is :

2q27. A uniform solid cylinder of base area 'A' is placed with its axis alongxaxis and one of the bases at the origin. The resistively of the

material changes according to the relation . (L = length of cylinder, is a positive constant) Resistance of the solid cylinder,across its ends is :Explanation:

28. What amount of heat will be generated in the circuit shown in figure after the switch SW is shifted from position 1 to position 2.


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Explanation:

And after shifting the switch

Let q = charge delivered by cell = = CE/3

29. An air capacitor of capacitance C0 is filled with isotropic dielectric whose dielectric constant varies from k1 to k2 (k1 > k2) in the direction

perpendicular to the plates. Find the capacitance of the capacitor after filling the gap.Explanation:

30.

n the figure shown,

[A] Energy stored in the capacitor is c[B] Potential difference between points A and B is 31 volts. C

[C] The current in is 2A c

[D] The current in is 4A


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31. An ideal ammeter is connected as shown. The reading of the ammeter is , find n.

Explanation:

and . reading of ammeter = towards left n = 7.

An circuit consists of a resistance R= 5 and a capacitance connected in series with battery. In how much time (insec) will the potential difference across the capacitor become 8 times that across the resistor ? (Given In 3 = 1.1)

Explanation:

given

=Initially the space between the plates of the capacitor is filled with air, and the field strength in the gap is equal to E0. Then half the gap (gap 2)

is filled with uniform isotropic dielectric of dielectric constant Kas shown. The final field strength in half air gap (gap 1) now becomes if

the voltage across the plates remains same. Find K.

Explanation:


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Capacitors+Dc Circuits