SSC JE Electrical Important MCQ Part 21


SSC JE Electrical Important MCQ PDF Part 21

1.In Figure if i = cos 4t and v = sin 4t, the element is


A. a resistor

B. a capacitor

C. an inductor


D. none of these

Answer : B

(Given i = cos 4t and v = sin 4t

We know cos x=sin (x+90⁰)

cos (4t)=sin (4t+90⁰)

So i = sin (4t+90⁰)—-(1)

v = sin 4t—-(2)

By equation (1) & (2) it clear voltage lags the current by 90o.

In purely capacitive circuit the alternating voltage lags the current by 90o.So element is a capacitor)

2.Voltage across 3μF capacitor is

A. 60V

B. 20V

C. 40V

D. 120V

Answer : C

(3μF is in series with 6μF=3×6/(9) =2μF

Now this 2μF is in parallel with 2μF=2+2=4 μF

v4μF = 1/2 x 120 = 60V

v2μF = 60V

v3μF =6*60/(6+3)= 40V)

3.Ceq for circuit in Fig

A. 1C

B. 2C

C. 4C

D. 12C

Answer : A

(Ceq of both parallel branches=C+C=2C,Now equivalent branches in series

So 1/Ceq =1/2C+1/2C=1/C or Ceq=1 C)

4.Leq in of the circuits in Fig.

A. 50 L

B. 500 L

C. 0.5 L

D. 5 L

Answer : C

(L//L = 0.5L

So L//L + L//L = L

Leq = L//L = 0.5L)

5.The charge entering a certain element is shown in Fig.The value of current at t = 1 ms is

A. 30 A

B. 0 A

C. -15 A

D. 15 A

Answer : D

(At t = 1ms, i=dq/dt=(30-0)/(2-0)=30/2=15 A

Note-dq,dt is the change in value in curve area for example At t = 10ms, i=dq/dt=(0-30)/(12-8)=-30/4=-7.5 A )

6.The V₀ in the circuit of Fig is

A. 18 V

B. 6 V

C. 20 V

D. 10 V

Answer : A

(Since Σ p = 0

-30×6 + 6×12 + 3V₀ + 28 + 28×2 – 3×10 = 0

72 + 84 + 3V₀ = 210 or 3V₀ = 54

V₀= 18 V)

7.Figure shows the power consumption of a certain household in 1 day. The total energy consumed in kWh, will be

A. 10 kWh

B. 100 kWh

C. 1.0 kWh

D. 20 kWh

Answer : A (Energy = Σpt = 200 x 6 + 800 x 2 + 200 x 10 + 1200 x 4 + 200 x 2= 10 kWh)

8.The number of branches and nodes in the circuit of Fig is

A.6 branches and 4 nodes

B.4 branches and 2 nodes

C.5 branches and 4 nodes

D.2 branches and 2 nodes

Answer : A

9.Value of currents i₁,i₂, and i₃ in the circuit shown in Fig

A. i₁=4 A,i₂=1 A,i₃=3 A

B. i₁=-4 A,i₂=1 A,i₃=-3 A

C. i₁=4 A,i₂=-1 A,i₃=-3 A

D. i₁=4 A,i₂=-1 A,i₃=3 A

Answer : B

(At node A, 8 = 12 + i₁ or i₁ = – 4A

At node C, 9 = 8 + i₂ or  i₂ = 1A

At node D, 9 = 12 + i₂ or i₂ = -3A)

10.Consider the Wheatstone bridge shown in Fig.,What will be vab

A. -5 V

B. 10 V

C. 15 V

D. 5 V

Answer : D

(Using voltage division

Va =12*25/(12+8)=15 V

Vb =10*25/(10+15)=10 V

Vab = 15 − 10=5 V)

11.Standardization of potentiometers is done in order that, they become

A. Accurate

B. Precise

C. Accurate and direct reading.

D. Accurate and precise

Answer : C

12. A potentiometer is basically a

A. Deflection type instrument

B. Null type instrument

C. Deflection as well as null type instrument

D. A digital instrument

Answer : B

13.Electronic null detectors are

A .Less sensitive

B. More sensitive.

C. More expensive.

D.Of excellent sensitivity, rugged construction and fairly expensive

Answer : D

14.The Recorder used for plotting B-H curves for magnetic materials

A. LVDT type recorder

B. Circular chart recorder

C. X-Y recorder

D. Potentiometer type recorder

Answer : C

15.Galvanometer type recorder use

A. Vibration galvanometer

B. Ballistic galvanometer

C. D’Arsonval galvanometer

D. Tangent galvanometer

Answer : C

16.The piezoelectric crystal sensitivity is defined as

A. Voltage developed per unit stress

B. Field developed per unit stress

C.Voltage developed per unit force

D.Field developed per unit force

Answer : B

17.Which one of the following is a passive transducer

A. Piezoelectric

B. Thermocouple

C. Photovoltaic cell

D. LVDT

Answer : D (Passive transducer is a device which converts the given non-electrical energy into electrical energy by external force. Resistance strain gauge, Differential Transformer/LVDT are the examples for the Passive transducers.)

18.Which of the following errors can arise, as a result of mistake in reading, parallax improper instrument location and inadequate lighting

A. Construction errors

B. Transmission errors

C. Observation errors

D. Translation errors

Answer : C

19.Relation between standard deviation and variance is

A. V = √σ

B. V = σ²

C. V = 1 / σ

D. V = 1/ √σ

Answer : B

20.A 0-1 mA meter has a sensitivity of

A.1 kΩ/V

B. 1 mA

C. 1 k Ω

D. 1000 A

Answer : A (sensitivity S=1/Ifsd=1/1 mA=1 kΩ/V)

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