Quiz: Electrical Engineering

Exam: UPSSSC JE

Topic: Network theorems

Each question carries 1 mark.

Negative marking: 1/4 mark

Time: 10 Minute

Q1. The RMS value of a sine wave is 100 A. Its peak value is

(a)77.7 A

(b)141 A

(c)250 A

(d)482.8 A

Q2. The average value of full-wave rectified sine wave with period π, and a peak value of Vm is

(a)0.777 Vm

(b)0.550 Vm

(c)0.637 Vm

(d)0.368 Vm

Q3. The rms value of voltage u(t) = 3 + 4 cos (3t) is

(a)√17V

(b)15 V

(c)77 V

(d)3 + 5√2 V

Q4. A particular current is made up of two components: a 10 A dc and a sinusoidal current of peak value of 14.14 A. The average value of the resultant current is

(a)Zero

(b)28.14 A

(c)10 A

(d)19.14 A

Q5. Pure inductive circuit

(a)Consume some power on average

(b)Does not consume power

(c)Takes power from the line during some part of cycle and then return back during other part of cycle.

(d)None of these

Q6. Unit of inductive reactance is

(a)Henry

(b)Millihenry

(c)Wb

(d)Ohm

Q7. Which of the following can produce maximum induced voltage?

(a)1 A dc current

(b)50 A dc current

(c)10 A 50 Hz ac current

(d)10 A 680 Hz ac current

Q8. A circuit component that opposes the change in the circuit voltage is

(a)Resistance

(b)Capacitance

(c)Inductance

(d)None of these

Q9. The pf of practical inductor is

(a)Zero

(b)Unity

(c)lagging

(d)leading

Q10. Due to skin effect the current flows

(a)Uniformly through the conductor

(b)Near the surface of conductor

(c)Through central core of conductor

(d)In the center of conductor

Solution

Sol.1 (b)

Peak value of sinusoidal wave,

Imax = √2 Irms

=√2 × 100 A

= 141 A

Sol.2 (c)

Average value of full-wave rectified sine wave with period π and a peak value of Vm

= 1/2π ∫_0^π▒〖v dϴ〗

= 1/2π ∫_0^π▒〖Vm Sin ϴ dϴ〗

=Vm/2π [- cos ϴ] lim 0 to π

= Vm/π

= .637 Vm

Sol.3 (a)

V rms = √((Vdc)^2+(Imax/√2)^2 )

= √17 V

Sol.4 (c)

I av = average value of dc component + average value of ac component

= 10 + 0

= 10 A

Sol.5 (c)

Takes power from the line during some part of cycle and then return back during other part of cycle.

Sol.6 (d)

Ohm is the unit of inductive reactance.

Sol.7 (d)

Magnitude of induced voltage is given as

E = L di/dt

= jωLI

I.e., the induced voltage is directly proportional to product of current and frequency.

Sol.8 (b)

Capacitance opposes the change in voltage in the circuit.

Sol.9 (c)

Lagging

Sol.10 (b)

Due to skin effect the current flows near the surface of conductor.