Upload
others
View
9
Download
0
Embed Size (px)
Citation preview
(22)508-RR(A) [ Turn over
O⁄´¤%lO⁄ ÆË√v⁄ ÃO⁄–y Æ⁄¬fiO¤– »⁄flMs⁄ÿ, »⁄fl≈Ê«fiÀ⁄ ¡⁄M, ∑ÊMV⁄◊⁄‡¡⁄fl — 560 003
KARNATAKA SECONDARY EDUCATION EXAMINATION BOARD, MALLESWARAM, BANGALORE – 560 003
G—È.G—È.G≈È.“. Æ⁄¬fiOÊ⁄–, d‡´È — 2019 S. S. L. C. EXAMINATION, JUNE, 2019
»⁄·¤•⁄¬ D}⁄ °¡⁄V⁄◊⁄fl
MODEL ANSWERS
¶´¤MO⁄ : 22. 06. 2019 ] —⁄MOÊfi}⁄ —⁄MSÊ¿ : 71
Date : 22. 06. 2019 ] CODE NO. : 71
…Œ⁄æ⁄fl : GΔ»ÊflMmÈ” A±È »ÊflO¤¿¨O⁄≈È @MsÈ
G≈ÊPoÒO⁄≈È BMf¨æ⁄fl¬MVÈ - 2
Subject : ELEMENTS OF MECHANICAL AND ELECTRICAL ENGINEERING-2
( ‘ʇ—⁄ Æ⁄p⁄¿O⁄√»⁄fl / New Syllabus ) ( Æ⁄‚¥´⁄¡¤»⁄~%}⁄ À¤≈¤ @∫⁄¥¿£%/ Regular Repeater ) [ V⁄¬Œ⁄r @MO⁄V⁄◊⁄fl : 100 [ Max. Marks : 100
Qn. Nos.
Sub. Qn.No. Value Points Marks
SECTION - A 1. a) Explain the functions of piston in an I.C. engine. 2
Ans.
Piston : It is a reciprocating part of the engine and
reciprocates to and fro inside the cylinder. The top of
the piston is suitable cavity and the lower part of the
piston is connected with connecting rod with the help
of a pin called as gudgeon pin.
2
A CCE RR REVISED
71 2 CCE RR
(22)508-RR(A)
Qn. Nos.
Sub. Qn.No. Value Points Marks
b) List the main applications of I.C. engines. 3
Ans.
Applications of I.C. engine are —
i) vehicles, locomotives, ships and aircrafts
ii) used for power generation
iii) used in farm tractors, lawn movers, concrete
mixing devices and motor boats
iv) used in agricultural applications.
3 × 1 = 3
c) Draw a neat sketch of four stroke diesel engine and
explain briefly. 5
Ans.
Four stroke diesel engine :
Diesel engine operates on diesel cycles and is operated
with diesel fuels. These engines are also called as
compression ignition engines. These engines do not
require ignition system, only air is admitted during
suction stroke and diesel fuel is injected with the help
of a suitable injector in to the compressed air within
the engine cylinder and air-fuel mixing takes place
inside the engine cylinder operates with higher
compression ratio and consumes less fuel.
Sketch = 3
Explanation = 2
5
CCE RR 3 71
(22)508-RR(A) [ Turn over
Qn. Nos.
Sub. Qn.No. Value Points Marks
2. a) Name the two types of air compressor. 2 Ans. i) Reciprocating air compressor ii) Centrifugal air compressor.
2 × 1 = 2
b) Explain the applications of air compressor. 3
Ans.
Applications of air compressor :
i) inflating tubes and tyres
ii) inflating baloons
iii) used in automobile workshop
iv) used in hospitals
v) used in painting industries
vi) used in bore well rigging machines.
3 × 1 = 3
c) Draw a neat sketch of single stage reciprocating air
compressor and label the parts. 5
Ans.
Single stage reciprocating air compressor.
Sketch = 3
Parts = 2
5
3. a) Mention the applications of air conditioning. 2
Ans.
Applications of Air Conditioning :
i) residential air conditioning : homes, hospitals,
auditoriums, theatres etc.
71 4 CCE RR
(22)508-RR(A)
Qn. Nos.
Sub. Qn.No. Value Points Marks
ii) commercial air conditioning : storage of foods and
other commodities, special applications
iii) industrial air conditioning : chemical, electronic,
tobacco, textile and software industries.
2 × 1 = 2
b) Explain the following properties of good refrigerant : 3
i) Stability
ii) Non-flammability
iii) Safety.
Ans.
Stability : refrigerant should be chemically
stable, non-toxic and inert.
Non-flammability : it should be non-explosive and
should not cause any fire hazard.
Safety : it should not corrode the parts or
materials used in construction
where it is passed through and
should not react with lubricating
oil.
3 × 1 = 3
c) Draw a neat sketch of winter air conditioning system
and label the parts. 5
Ans.
Winter Air conditioning system.
Sketch = 3
Parts = 2
5
CCE RR 5 71
(22)508-RR(A) [ Turn over
Qn. Nos.
Sub. Qn.No. Value Points Marks
4. a) List out the work holding devices on a lathe. 2
Ans.
i) centres
ii) carriers and catch plates
iii) chucks
iv) face plates
v) mandrels.
4 × ½ = 2
b) What are the operations which are performed on the
lathe by holding the job in between the centres by
chuck ? 3
Ans.
Turning, facing, chamfering, parting, grooving,
knurling, thread cutting, polishing.
3 × 1 = 3
c) Calculate the half taper angle for taper turning by tail-
stock offset method when larger diameter is 30 mm
and smaller diameter is 25 mm and length of taper is
50 mm. 5
Ans.
Taper of conicity = D − d
l
Half taper angle = D − d
2l
Set over(s) = 1 × half taper angle
Set over(s) 1 × 30 − 25
2 × 50
Set over(s) =
5100
= 0 ⋅ 05
Formula = 2
Substitution = 2
Result = 1
5
OR
71 6 CCE RR
(22)508-RR(A)
Qn. Nos.
Sub. Qn.No. Value Points Marks
a) Name the differential types of milling cutters. 2
Ans.
Plain milling cutter, Side milling cutter, Angle milling
cutter, End milling cutter, slot milling cutters.
4 × ½ = 2
b) What do you understand by up-milling and down-
milling ? Explain. 3
Ans.
Up-milling : it is also called as conventional milling in
which the direction of rotation of cutter and the feed
are in the opposite directions.
Down-milling : It is also called as climb milling in which
the directions of rotation of cutter and the feed are in
the same direction.
1½ +1½ = 3
c) A 25 mm thick M.S. plate is to be drilled 25 mm drill
with a cutting speed 25 m/min during the operation.
How much spindle speed is to be adopted ? 5
Ans.
d = 25 mm = 0·025 m, t = 25 mm = 0·025 m
v = 25 m/min
1000dNv π= m/min
N =
1000 vπd
= 1000 × 25π × 25
= 318 RPM
Formula = 2
Substitution = 2
Result = 1
5
CCE RR 7 71
(22)508-RR(A) [ Turn over
Qn. Nos.
Sub. Qn.No. Value Points Marks
5. a) What is brazing ? 2 Ans. Brazing : it is a process of joining two metal pieces with the help of non-ferrous filler metal at a comparatively higher temperature of about more than 450˚C. This process is most suitable for joining dissimilar metal and filler rod used must be made up of non-ferrous metal — commonly used fluxes are borax fluorides, chlorides and boric acid.
2
b) Explain the advantages of soldering. 3 Ans. Advantages of soldering : i) dissimilar metals can be joined ii) it is simple low cost, flexible, economical, and user
friendly iii) The life of solder will be more iv) Low amount of power is required to heat the
soldering iron v) The soldering can be done at low temperature and
controlling is very easy vi) soldered joints can be dismantled.
3 × 1 = 3
c) Draw a neat sketch showing all the equipment of metal arc welding. 5 Ans.
Equipment of metal arc welding.
Sketch = 4 Parts = 1
5
71 8 CCE RR
(22)508-RR(A)
Qn. Nos.
Sub. Qn.No. Value Points Marks
SECTION – B
6. a) Define statically induced emf. 2 Ans. The e.m.f. induced in a conductor due to variations of flux linking with conductor, when both the magnetic field and the conductor are stationary is called the statically induced e.m.f.
2
b) Explain Fleming’s right hand rule. 3 Ans. Fleming’s right hand rule : Stretch the fore finger and the thumb of your right hand at right angles to each other. The fore finger indicates the direction of flux, the thumb indicates motion of the conductor and middle finger indicates the direction of e.m.f. induced in the conductor.
3
c) Draw a neat sketch of self induced emf and explain it briefly. 5 Ans.
Self induced e.m.f. sketch
The e.m.f. induced in a coil due to changing flux created the current flowing through the same coil is called self induced e.m.f. This is always in opposition to the applied voltage and is measured in volts. Sketch = 3 Explanation = 2
5
CCE RR 9 71
(22)508-RR(A) [ Turn over
Qn. Nos.
Sub. Qn.No. Value Points Marks
7. a) Define form factor. 2
Ans.
It is defined as the ratio of r.m.s. value to average value
of an alternating quantity.
Form factor =
r.m .s. valueaverage value
= 0 ⋅ 7070 ⋅ 637
= 1 ⋅11
2
b) Describe power and power factor of an a.c. circuit. 3
Ans.
Power : power consumed by a single phase a.c. circuit
is given by the product of the applied voltage to the
circuit and the in phase component of current in the
circuit. It is expressed in watts or kilowatts.
Power factor : cosine of the angle ( φ) between applied
voltage and the total current in the circuit is called
power factor of that circuit.
Power factor = cos φ
2 × 1½ = 3
c) Draw a neat diagram of sinusoidal waveform and mark
the following : 5
i) negative
ii) amplitude
iii) positive.
Ans.
Sketch = 2
Marking = 3
5
71 10 CCE RR
(22)508-RR(A)
Qn. Nos.
Sub. Qn.No. Value Points Marks
8. a) What is transformer ? 2
Ans.
Transformer is a static electromagnetic device which
transfers electrical energy from one ac circuit to
another circuit either at the same voltage or at a
different voltage but at the same frequency.
2
b) Explain the working principle of d.c. motor. 3
Ans.
A dc motor works on the principle that whenever a
current carrying conductor is placed in a magnetic field
it experiences a force and tends to move at right angle
to the direction of the main field.
The direction of rotation of the conductor is determined
by Fleming’s left hand rule.
F = BLI newtons
B = flux density measure in Wb 2m/
L = Length of the conductor in m
I = current in the conductor in amps.
3
c) How does the step-up transformer differ from step-
down transformer ? 5
Ans.
CCE RR 11 71
(22)508-RR(A) [ Turn over
Qn. Nos.
Sub. Qn.No. Value Points Marks
If the transformer takes power at a lower voltage and delivers power at a higher voltage it is called step-up transformer.
212121 , , IIEENN ><<
Step-down transformer
When the transformer takes power at a higher voltage
and delivers power at a lower voltage it is called step-
down transformer.
121212 , , IIEENN ><<
2 × 2 = 5
OR
a) What is d.c. generator ? 2 Ans. DC generator is electromagnetic machine which converts mechanical energy into electrical energy.
2
b) Explain squirrel cage induction motor. 3
Ans.
Explanation
71 12 CCE RR
(22)508-RR(A)
Qn. Nos.
Sub. Qn.No. Value Points Marks
Squirrel cage rotor, rotor windings consist of
aluminium or copper bars of rectangular cross-section
moulded into the slots of the rotor core. These bars are
shorted at both ends by thick copper rings. The rotor
winding appears as a cage and hence it is called
squirrel cage induction motor.
3
c) How does the d.c. series generator differ from d.c.
shunt generator ? 5
Ans.
It is a self existed DC generator in which the field
winding is connected in series with the armature
winding. Field winding has less number of turns of
thick wire and has low resistance.
It is a self excited dc generator in which the field
windings are connected parallel with the armature
winding. Field winding has more number of turns of
thin wire and has high resistance.
2 × 2½ = 5
CCE RR 13 71
(22)508-RR(A) [ Turn over
Qn. Nos.
Sub. Qn.No. Value Points Marks
9. a) Explain thermostat. 2
Ans.
Thermostat controls the operation of most of the
heating appliances acting as a switch it connects to a
bi-metal strip.
2
b) Mention the parts of electric stove. 3
Ans.
Parts of Electric stove :
i) Metal body or Frame
ii) Heater plate made of china clay or porcelain
iii) Heating element is made of nichrome wire
iv) Terminals with nuts and washers
v) Porcelain bushes for terminal
vi) Supply cord, plug top and connector.
6 × ½ = 3
c) Draw a neat sketch of a.c. ceiling fan and label the
parts. 5
Ans.
A.C. ceiling fan sketch and parts
Sketch = 3
Parts = 2
5
71 14 CCE RR
(22)508-RR(A)
Qn. Nos.
Sub. Qn.No. Value Points Marks
10. a) Explain the heating element of electric iron. 2
Ans.
Heating element is made of nichrome strip wound on
the mica piece and insulated with mica on both sides
which is kept under the pressure plate.
2
b) Differentiate between diode and transistor. 3
Ans.
Diode : It is a two element semiconductor device
formed by joining a piece of P-type semiconductor to a
piece of N-type semiconductor by a suitable technique.
Transistor : Transistor is a three terminal
semiconductor device formed by sandwiching a layer of
one type of semiconductor ( P or N ) in between two
layers of another type of semiconductor ( N or P ).
1½ × 2 = 3
c) Draw a neat sketch of reverse bias of a P-N junction
diode and explain it briefly. 5
Ans.
When an external voltage source is applied to the diode
such that the positive terminal of the battery is
CCE RR 15 71
(22)508-RR(A) [ Turn over
Qn. Nos.
Sub. Qn.No. Value Points Marks
connected to N-type semiconductor and the negative
terminal to a P-type semiconductor the diode is said to
be reverse biased.
Sketch = 2½
Explanation = 2½
5