**1.** The efficiency of the DC motor at maximum power will be ________

- 100%
- Around 90%
- Anywhere between 75% and 90%
- Less than 50%

**2.** Constant losses of DC motor can be measured by:

- Swinburne’s Test
- Retardation Test
- Hopkinson’s Test
- Load Test

**3.** The No-Load Test in DC Motor is known as ______

- Swinburne’s Test
- Retardation Test
- Hopkinson’s Test
- Load Test

**4. **The efficiency of a DC motor is defined as _______.

- η = input power / (input power – losses)
- η = output power / (input power – losses)
- η = (input power – losses) / input power
- η = output power / (input power + losses)

**5.** The hysteresis loss in a DC machine least depends on ______

- Frequency of magnetic reversals
- Maximum value of flux density
- Volume and grade of iron
- Rate of flow of ventilating air

**6.** Find the current required by a 400 V, 10 H.P. DC motor at 73.55% efficiency.

- 35 A
- 20 A
- 30 A
- 25 A

**7.** Which of the following test is usually conducted to determine the efficiency of traction motors?

- Field’s test
- Swinburne’s test
- Hopkinson’s test
- Retardation test

**8.** Which of the following is not the effect of iron loss?

- Loss of efficiency
- Excessive heating of core
- Increase in terminal voltage
- Rise in temperature of ventilating air

**9.** A 500 V shunt motor takes 2 A on no-load. The armature resistance is 0.1 ohms and field current is 1 A. Brush resistance is negligible. If the line input current is 50 A then the efficiency will be

- 100%
- 50%
- 95%
- 90%

**10.** The gross mechanical power developed by the motor is maximum when the back EMF is equal to _______ of the supply voltage.

- Twice
- 2/3
- 1/2
- 1/3

**11.** Which of the following loss is likely to have the highest proportion at the rated load of the DC Motor?

- Hysteresis loss
- Field copper loss
- Armature copper loss
- Eddy current loss

**12.** A 400 V shunt motor has armature resistance 0.5 Ω and field resistance of 100 Ω. If the motor is delivering 10 kW at 90% Efficiency. Then the value of induced emf will be

- 388.11 V
- 367.54 V
- 351.23 V
- 391.91 V

**14.** ________ test in DC Machine is carried on Full load

- Swinburne’s Test
- Retardation Test
- Hopkinson’s Test
- Load Test

**15.** What is M. N. A. in the context of DC motors?

- Minimum Natural Alignment
- Magnetic Neutral Axis
- Magnetized Natural Alignment
- None of these

**16.** Which of the following loss in a DC generator varies significantly with the load current?

- Field copper loss
- Windage loss
- Armature copper loss
- Cannot be determined

**17.** The total losses in a well-designed DC generator of 10 kW will be nearly equal to ______

- 100 W
- 500 W
- 1000 W
- 1500 W

**18.** Which of the following methods is likely to result in a reduction of hysteresis loss in a DC Machine?

- Providing laminations in armature core
- Providing laminations in stator
- Using non-magnetic material for frame
- Using material of low hysteresis coefficient for armature core material

**19.** Which of the following losses are significantly reduced by laminating the core of a DC machine?

- Hysteresis losses
- Eddy current losses
- Copper losses
- Windage losses

**20.** Which of the following loss/losses in a DC generator is dissipated in the form of heat?

- Mechanical loss
- Core loss
- Copper loss
- Mechanical, Copper and Core