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/Ï€
= .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.
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