1. The unit of voltage is Pascal.
a) True
b) False
Explanation: The voltage is equal to one volt when 1 A of current flows through 1 Ω resistor. It is mathematically represented as I×R. It is expressed in terms of a volt(V).
2. Calculate the moment of inertia of the sphere having a mass of 8.4 kg and radius of 61 cm.
a) 3.124 kgm2
b) 3.125 kgm2
c) 4.545 kgm2
d) 5.552 kgm2
Explanation: The moment of inertia of the egg can be calculated using the formula I=Σmiri2. The mass of egg and radius is given. I=(8.4)×(.61)2=3.125 kgm2. It depends upon the orientation of the rotational axis.
3. The most suitable control-motor application is __________
a) AC shunt motor
b) DC separately motor
c) AC one-phase induction motor
d) DC shunt motor
Explanation: DC separately motor has definite full-load speed, so they don’t ‘run away’ when the load is suddenly thrown off provided the field circuit remains closed. The speed for any load within the operating range of the motor can be readily obtained.
4. In a DC series motor, the e.m.f developed is proportional to _______
a) N×Ia
b) N×Ia2
c) N×Ia3
d) N×Ia.5
Explanation: In a DC series motor, the e.m.f developed is equal to KmΦN. In a DC series, the motor field winding is connected in series with the armature so the flux in the field winding is proportional to current. Eb = KmΦN α Ia×N.
5. Calculate the value of the time period if the frequency of the signal is .07 sec.
a) 14.28 sec
b) 14.31 sec
c) 14.23 sec
d) 14.78 sec
Explanation: The time period is defined as the time after the signal repeats itself. It is expressed in second. T = 1÷F=1÷.07=14.28 sec.
6. The slope of the V-I curve is 13.89°. Calculate the value of resistance.
a) .247 Ω
b) .345 Ω
c) .231 Ω
d) .222 Ω
Explanation: The slope of the V-I curve is resistance. The slope given is 13.89° so R=tan(13.89°)=.247 Ω. It behaves like a normal resistor.
7. In a DC shunt motor, the e.m.f developed is proportional to ___________
a) Ia
b) Ia2
c) Ia3
d) Iao
Explanation: In a DC shunt motor, the e.m.f developed is equal to KmΦN. In a DC shunt, the motor field windings are connected separately and excited by a constant DC voltage. E = KmΦN α Ia°.
8. Calculate the power factor angle during the resonance condition.
a) 0°
b) 10°
c) 80°
d) 90°
Explanation: During the resonance condition, the reactive power generated by the capacitor is completely absorbed by the inductor. Only active power flows in the circuit. Net reactive power is equal to zero and Φ=0°.
9. Calculate the value of the duty cycle if the system is on for 5 sec and off for inf sec.
a) 0
b) .4
c) .2
d) .1
Explanation: Duty cycle is Ton÷Ttotal. It is the ratio of time for which the system is active and the time taken by the signal to complete one cycle. D = Ton÷Ttotal=5÷inf=0.
10. Calculate the value of the frequency of the AC supply in India.
a) 0 Hz
b) 50 Hz
c) 49 Hz
d) 60 Hz
Explanation: The frequency is defined as the number of oscillations per second. It is reciprocal of the time period. AC supply magnitude is variable. It changes with time so the frequency of AC supply is 50 Hz.