Quiz: Electrical Engineering 03 Mar 2021

Quiz: Electrical Engineering
Exam: UPPCL-JE
Topic: Miscellaneous

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

Q1. A 15 V source is connected across a 12 Ω resistor. How much energy is used in 3 minutes?
(a) 5.6 Wh
(b) 938 Wh
(c) 0.938 Wh
(d) 56.25 Wh

Q2. When the speed at which a conductor is moved through a magnetic field is increased, the induced voltage
(a) Remains constant
(b) Increases
(c) Decreases
(d) Reaches zero

Q3. Three lights are connected in parallel across a 120-volt source. If one light burns out,
(a) The remaining two will not glow
(b) The remaining two will glow dimmer
(c) The remaining two will grow brighter
(d) The remaining two will glow with the same brightness as before

Q4. Two capacitor C1 and C2 have C1=20μ F and C2 = 30μ F, are connected in parallel
across a 100V source. The net capacitance of the circuit is?
(a) 50 μ F
(b) 10 μ F
(c) 12 μ F
(d) 60 μ F

Q5. A 100mA meter has accuracy of +2%. Its accuracy while reading 50mA will be:
(a) +1%
(b) +2%
(c) +4%
(d) +20%

Q6. The current through the 2 kΩ resistance in the circuit shown is

(a) 0 mA
(b) 1 mA
(c) 2 mA
(d) 6 mA

Q7. Which of the following statement is true?
(a) At higher voltage, cost of transmission is reduced
(b) At higher voltage, cost of transmission is increased
(c) Both a and b
(d) None of the above

Q8. In order to obtain higher efficiency for 3-phase induction motors, its slip should be:
(a) Low
(b) 1
(c) High
(d) Very high

Q9.A CRO is used to measure
(a) Voltage
(b) frequency
(c) phase
(d) All of these

Q10.A MOSFET has………terminals.
(a) two
(b) five
(c) four
(d) three

SOLUTIONS
S1. Ans.(c)
Sol. P=V^2/R=(15)^2/12=225/12 W
And t=3 minutes=3/60 hours
∴W=P×t=225/12×3/60=0.938 Wh

S2. Ans.(b)
Sol. e=BlV sin⁡Ө
So, e α v
So, when speed is increased the induced voltage will also increase.

S3. Ans.(d)
Sol. Three lights are connected in parallel across a 120-volt source. If one light burns out, the remaining two will glow with the same brightness as before because the voltage across other two light will not change.

S4. Ans.(a)
Sol. C_eq=C_1+C_2
= 30μF + 20μF
= 50 μF

S5. Ans.(c)
Sol. Error = 100 mA ×(±2)/100= ±2mA
% error = (±2mA)/50mA×100= ±4%

S6. Ans.(a)
Sol. it is a balanced wheat stone bridge.

S7. Ans.(a)
Sol. At higher voltage, volume of conductor is reduced. Area of conductor A ∝ 1/Vs² Where Vs = Supply voltage So that material requirement is reduced and hence cost of the material and transmission is reduced.

S8. Ans.(a)
Sol. for 3-phase induction motor, in order to obtain higher efficiency its slip should be low. i.e., rotor speed should be approx. equivalent to synchronous speed. (N≃N_S) .
Rotor efficiency =NR/NS 0R (1-S). So, if rotor speed is approx. equal to synchronous speed, then efficiency will be maximum. i.e., slip should be low.

S9. Ans.(d)
Sol. CRO can measure voltage, frequency, phase but not the current.

S10. Ans.(d)
Sol.

Schematic symbol of n-channel MOSFET