1.The phase difference between voltage and current in the inductor.
a) 45°
b) 90°
c) 80°
d) 55°
Explanation: In the case of an inductor, the voltage leads the current by 90° or the current lags the voltage by 90o. The phase difference between voltage and current is 90°.
2. The phase difference between voltage and current in the resistor.
a) 85°
b) 90°
c) 0°
d) 5°
Explanation: In the case of a resistor, the voltage and current are in the same phase. The phase difference between voltage and current is 0°. The voltage drop in the resistor is given as V=IR
3. The phase difference between voltage and current in the capacitor.
a) 90°
b) 80°
c) 95°
d) 91°
Explanation: In the case of a capacitor, the voltage lags the current by 90° or the current leads the voltage by 90o. The phase difference between voltage and current is 90°
4. The slope of the I-V curve is 30°. Calculate the value of resistance. Assume the relationship between I and V is a straight line.
a) 1.732 Ω
b) 2.235 Ω
c) 1.625 Ω
d) 1.524 Ω
Explanation: The slope of the I-V curve is reciprocal of resistance. The slope given is 30° so R=1÷tan(30°)=1.732 Ω. The slope of the V-I curve is resistance
5. What is a mark to space ratio?
a) Ton÷Toff
b) Ton÷(Ton- Toff)
c) Ton÷2×(Ton*Toff)
d) Ton÷2×Toff
Explanation:Mark to space is Ton÷Toff. It is the ratio of time for which the system is active and the time for which is inactive. It has no unit.
6. What is the formula for the moment of inertia? (m – a mass of the body, r – distance from the axis of the rotation)
a) ∑miri2
b) ∑miri
c) ∑miri4
d) ∑miri3
Explanation: The moment of inertia is the property by the virtue of which the body withstand the effect of angular acceleration. It depends on the shape and mass distribution of the body
7. The generated e.m.f from 50-pole armature having 400 conductors driven at 20 rev/sec having flux per pole as 30 mWb, with lap winding is ___________
a) 230 V
b) 140 V
c) 240 V
d) 250 V
Explanation: The generated can be calculated using the formula Eb = Φ×Z×N×P÷60×A, Φ represent flux per pole, Z represents the total number of conductors, P represents the number of poles, A represents the number of parallel paths, N represents speed in rpm. In lap winding number of parallel paths are equal to the number of poles. Eb = .03×50×400×1200÷60×50= 240 V.
8.The unit of the moment of inertia is Kgm2.
a) True
b) False
Explanation: The moment of inertia is taken as the sum of the product of the mass of each particle with the square of their distance from the axis of the rotation. The unit of the moment of inertia is kg×m2=kgm2.
9. Calculate the moment of inertia of the egg having a mass of 7 kg and radius of 44 cm.
a) .968 kgm2
b) 1.454 kgm2
c) 1.545 kgm2
d) 1.552 kgm2
Explanation: The moment of inertia of the egg can be calculated using the formula I=∑miri2. The mass of egg and radius is given. I=(7)×(.44)2=1.552 kgm2. It depends upon the orientation of the rotational axis
10. Which of the theorems helps in the calculation of the moment of inertia?
a) The theorem of Parallel and Perpendicular axes
b) The theorem of Horizontal and Perpendicular axes
c) The theorem of Vertical and Perpendicular axes
d) The theorem of Parallel and Tilted axes
Explanation: The theorem of Parallel and Perpendicular axes helps in the calculation of the moment of inertia. The moment of inertia of the complex bodies can be easily calculated with the help of these theorems.