Karnataka SSLC Question Paper 2025 Answer Key Elements of Electrical Engineering

Government of Karnataka
Karnataka Secondary Education Examination Board

Question Paper
ANSWER KEY

A
CCE RF/RR
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Subject : ELEMENTS OF ELECTRICAL ENGINEERING-IV
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Date : 01. 04. 2025 ] [ Max. Marks : 80

Qn.
Value Points Total
1. The S.I. unit of frequency is

(A) hertz (B) ampere

(C) volt (D) watt

(A) hertz 1

2. For a sine wave RMS value is

(A) 0·637 (B) 1·11

(C) 0·707 (D) 1·414

(C) 0·707 1

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Qn.
Value Points Total
3. The core of an alternator is made of

(A) Brass (B) Silicon steel

(C) Aluminium (D) Copper

(B) Silicon steel 1

4. An A.C. generator converts

(A) Mechanical energy into DC electrical energy

(B) Mechanical energy into chemical energy

(C) Electrical energy into mechanical energy

(D) Mechanical energy into A.C. electrical energy

(D) Mechanical energy into A.C. electrical energy 1

5. In step-up transformer

(A) N1 < N 2 (B) I1 = I 2

(C) N1 > N 2 (D) N1 = N 2

(A) N1 < N 2 1

6. Electrical bell is an example for

(A) heating effect (B) lighting effect

(C) chemical effect (D) magnetic effect

(D) magnetic effect 1

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Qn.
Value Points Total
7. Which of the following is a non-renewable source of

energy ?

(A) Hydroelectric energy

(B) Solar energy

(C) Nuclear energy

(D) Wind energy

(C) Nuclear energy 1

8. Which of the following power plants uses coal ?

(A) Solar power plant

(B) Nuclear power plant

(C) Thermal power plant

(D) Hydroelectric power plant

(C) Thermal power plant
1
9. An impurity which accepts the electron is called

(A) Acceptor impurity

(B) Pentavalent impurity

(C) Donor impurity

(D) Trivalent impurity

(A) Acceptor impurity
1

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Qn.
Value Points Total
10. A pure semiconductor is called

(A) Extrinsic semiconductor

(B) P-type semiconductor

(C) Intrinsic semiconductor

(D) N-type semiconductor

(C) Intrinsic semiconductor 1

11. a) Define A.C.

The current which changes both magnitude and

direction at regular intervals of time is called

alternating current. 2

b) Explain the following terms :

i) RMS value

ii) Frequency

i) RMS value

When direct current flows through a given circuit

for a given time produces heat as produced by

alternating current for the same time is called

RMS value.

Irms = 0·707

Vrms = 0·707

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Qn.
Value Points Total
ii) Frequency :

Number of cycles completed by an alternating

quantity in one second is called frequency. It is

measured in hertz. 1 + 1

c) Draw the neat diagram of sine wave and mark the
following :
i) Positive half-cycle
ii) Amplitude

3+2
12. a) Define A.C. Generator.
A.C. Generator
A.C. Generator is a electromagnetic machine which
converts mechanical energy into alternating current
electrical energy. 2
b) List the types of induced emf.
Types of emf
i) Dynamically induced emf
ii) Statically induced emf
a) Self-induced emf
b) Mutually induced emf
3

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Qn.
Value Points Total
c) Explain the phenomenon of electromagnetic

induction.

Phenomenon of electromagnetic induction :

When the magnet moved into the coil galvanometer

deflect indicates emf induced in the coil. When we

remove again galvanometer deflect in opposite

direction and indicates emf induced in the coil. If we

keep the magnet constant the no-flux cut by the coil

and induced emf is zero. This shows emf is induced in

the coil when their is a relative motion between the

coil and magnetic flux.
2+3
13. a) List the applications of diode.

Applications of diode :

1) used in rectifiers

2) used in clipping circuit

3) used in clamping circuit

4) used in voltage regulators.
2

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Qn.
Value Points Total
b) Explain Faraday’s law of electromagnetic induction.

First law : It states that "whenever changing flux

linking with the conductor induces emf."

Second law : "The magnitude of induced emf is

directly proportional to the rate of change of flux

linking with the conductor."

dφ
e =N in volts. 1 + 1
dt
3
c) Draw a neat diagram of squirrel cage rotor induction

motor and label the parts.

Squirrel cage rotor induction motor :

3+2
14. a) Define semiconductor.

Semiconductor : If the conductivity of the material lies

between conductor and insulator then it is called

semiconductor. Ex : Germanium.
2

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Qn.
Value Points Total
b) Write any three applications of transformer.

Application of transformer :

1) used in generating stations

2) used in sub-stations

3) used for distribution of power

4) small transformer used in TV electronic goods,

mobile charges, etc. 1+1+1
3
c) Draw a neat diagram of transformer and label the

parts.

Transformer :

3+2
15. a) List the sources of energy.

Source of energy :

1) Renewable sources of energy

2) Non-renewable sources of energy
1+1

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Value Points Total
b) Write short notes on solar power plant.

Solar power plant :

When sunrays made fall on the photovoltaic cell

(silicon cells) electricity is generated. This generates

D.C. power only. Hence it is stored in the secondary

cells. This is converted into A.C. by solar inverters,

then it is used. Whenever necessary, presently these

solar plants used in traffic signals, street lighting in

the cities. These plants are free from ash, smoke and

cheaper compared to other plants.
3
c) Draw the neat diagram of hydroelectric power plant

and label the parts.

Hydroelectric power plant :

3+2

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Qn.
Value Points Total
16. a) Draw the symbolic representation of N-P-N transistor.

Symbolic representation of N-P-N transistor :

2
b) Write the comparison between renewable and non-

renewable sources of energy.

Comparison :

Renewable sources Non-renewable sources

1. These sources are These sources are

available regularly available for short period

and they can be of time

stored

2. They produce ash, They are free from ash,

smoke, dust smoke, dust

3. To exist plant it need They need less space
large space compare to them

4. Cost of the plant is Cost of the plant is less

very high
1 + 1

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Qn.
Value Points Total
c) Draw a neat diagram of electrical fan and label the

parts.

Electric fan :

3+2
17. a) Define doping.

Doping : It is the process of adding impurity to the

pure semiconductor called doping.
2
b) Explain the following terms :

i) Average value

ii) Power factor

i) Average value :

When direct current flows in the circuit for a

given period of time it transfers heat as

transferred by A.C. for the same period of time.

ii) Power factor :

the cosine of the angle between applied voltage

( V ) and total current ( I ) in the circuit is called

power factor.
1 + 1

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Qn.
Value Points Total
c) Explain with neat sketch forward biasing of diode.

Forward biasing :

When positive terminal is connected to P-type

semiconductor and negative terminal is connected to

N-type semiconductor, then it is said to be forward

biased.

In forward biasing electrons are repelled by negative

terminal & holes are repelled by positive terminal.

Hence it reduces potential barrier, electron cross &

move to left through holes. Similarly holes move to

right and conducts flow of electric current.
2+3

CCE RF/RR(A)/101/1829 (MA)

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