Quiz: Electrical Engineering 28 Sep 2020

Quiz: Electrical Engineering
Exam: SSC JE
Topic: Miscellaneous

Each question carries 1 mark.
Negative marking: 1/4 mark
Time: 10 Minute

Q1. What will be the potential difference (in v) between the ends of a conductor when the current flowing through the conductor is 3 A and the value of conductance is 0.3 mho?
(a) 10
(b) 100
(c) 20
(d) 0.1

Q2. Determine the value of charge stored (in mC) in a capacitor, when the value of capacitance is 0.01 mF and the potential difference between the ends of the capacitor is 20 V.
(a) 0.2
(b) 2
(c) 20
(d) 200

Q3. What will be the value of load impedance (in ohms) for transmitting maximum power from the source to load when the source impedance is 8 + j4 ohms?
(a) 8 – j4
(b) 8 + j4
(c) 4 + j8
(d) 4 – j8

Q4. Determine the value of current (in A) drawn from the voltage source for the electric circuit given below.

(a) 4
(b) 3.5
(c) 2.5
(d) 1.6

Q5. Which of the following is the dimensional formula for inductance?
(a) ML^2 T^2 A^(-2)
(b) ML²T²A²
(c) ML^2 T^(-2) A^(-2)
(d) ML^(-2) T²A²

Q6. Which of the following is the CORRECT expression for hysteresis loss occurring in a material?
(a) η×Bm^2×f^2×V
(b) η×Bm^2×f^2×V^2.5
(c) η×Bm^1.6×f×V
(d) η×Bm^2×f^1.6×V

Q7. Which of the following expression satisfies the Faraday’s law of electromagnetic induction?
(a) e= -Ndϕ/dt
(b) e=N\/ dϕ/dt
(c) e= -N⎰dϕdt
(d) e=(Nd^2 ϕ)/(dt^2 )

Q8. Which property of a material opposes the passage of magnetic flux through it?
(a) Permeance
(b) Capacitance
(c) Inductance
(d) Reluctance

Q9. Which of the following statement is TRUE?
(a) A galvanometer can be converted into ammeter by connecting a low value of resistance in series with the galvanometer.
(b) a galvanometer can be converted into ammeter by connecting low value of resistance in parallel with the galvanometer.
(c) A galvanometer can be converted into ammeter by connecting a high value of resistance in series with the galvanometer.
(d) A galvanometer can be converted into ammeter by connecting a high value of resistance in parallel with the galvanometer.

Q10. Which of the statement is TRUE about megger?
(a) megger is used for the measurement of voltage.
(b) megger is used for the measurement of current.
(c) Megger is used for the measurement of insulation resistance.
(d) Megger is used for the measurement of breakdown voltage of insulation.

SOLUTIONS
S1. Ans.(a)
Sol. conductance(G)=1/R=0.3 mho
∴R=1/G=1/(0.3 ) Ω
∴potential difference(V)=IR=3×1/0.3=10 V

S2. Ans.(a)
Sol. from the expression, Q=CV
⇒Q=0.01×20=0.2 mC

S3. Ans.(a)
Sol. for maximum power transfer, ZL=ZS^* i.e. conjugate of source impedance
Given that, Z_S=8+j4
∴ZL=ZS^*=8-j4 ohm

S4. Ans.(c)
Sol.

Reqv=(20‖20)+(20‖20)=20 Ω
∴I=V/R=50/20=2.5 A

S5. Ans.(c)
Sol. We have the formula for inductance as,L=V/(dI/dt)

Hence, dimensional formula for inductance is [L]= [[ML^2 T^(-3) A^(-1) ]/[AT^(-1) ] ]=[ML^2 T^(-2) A^(-2)]

S6. Ans.(c)
Sol. The equation for hysteresis loss is given as:
Pb = η * Bmaxn * f * V
Pb = hysteresis loss (W)
η = Steinmetz hysteresis coefficient, depending on material (J/m3)
Bmax = maximum flux density (Wb/m2)
n = Steinmetz exponent, ranges from 1.5 to 2.5, depending on material
f = frequency of magnetic reversals per second (Hz)
V = volume of magnetic material (m3)

S7. Ans.(a)
Sol. expression for the Faraday’s law of electromagnetic induction: e= -Ndϕ/dt

S8. Ans.(d)
Sol. The obstruction offered by a magnetic circuit to the magnetic flux is known as reluctance. As in electric circuit, there is resistance similarly in the magnetic circuit, there is a reluctance, but resistance in an electrical circuit dissipates the electric energy and the reluctance in magnetic circuit stores the magnetic energy.

The differences between reluctance and permeance have been discussed in the table below.

Reluctance Permeance
Reluctance opposes the production of
magnetic flux in a magnetic circuit.
Permeance is a measure of the ease with
which magnetic flux can be set up in the magnetic circuit.
It is denoted by S. It is denoted by P.
Its unit is AT/Wb or 1/Henry or H-1. Its unit is Wb/AT or Henry.
It is analogous to resistance in an electric circuit. It is analogous to conductance in an electric
circuit.
Reluctance adds in a series of the
magnetic circuit.
Permeance adds in a parallel magnetic
circuit.

S9. Ans.(b)
Sol. A good ammeter has very low resistance. So, a moving coil galvanometer is converted into an ammeter by connecting a very low shunt resistance in parallel to the galvanometer resistance.
A good voltmeter has very high resistance. So, a moving coil galvanometer is converted into a voltmeter by connecting a high resistance in series with the galvanometer resistance.

S10. Ans.(c)
Sol. Megger is used for the measurement of insulation resistance.

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