# Single Phase Motors 1

Objectives for Electrician and Wireman: Single Phase Motors 1

Subject: Single Phase Motors 1

Part 1: Objective questions and answers of Single Phase Motors

Q1. What is the working principle of single phase induction motor?

a) Lenz's law

b) Joule's law

d) Faraday's laws of electromagnetic induction

Q2. Which type of A.C single phase motor is classified under commutator motor type?

a) Stepper motor

b) Repulsion motor

d) Permanent capacitor motor

Q3. Which type of winding wire is used for rewinding submersible pumps?

a) PVC covered copper wire

b) Super enamelled copper wire

c) Single cotton covered copper wire

d) Double cotton covered copper wire

Q4. Which is the application of universal motor?

a) Jet pump

b) Food mixer

c) Teleprinter

d) Compressor

Q5. What is the relation between running winding and starting winding of a single phase induction motor with respect to resistance?

a) Both resistances will be equal

b) Running winding is less, starting winding more

c) Running winding is more, starting winding less

d) Running winding is less, starting winding infinity

Q6. Which single phase motor tapped field speed control method is employed?

a) Universal motor

c) Capacitor start induction run motor

d) Capacitor start capacitor run motor

Q7. What is the angular displacement between starting and running winding of a single phase induction motor?

a) 45 electrical degree

b) 60 electrical degree

c) 90 electrical degree

d) 120 electrical degree

Q8. Which motor is preferred for domestic water pumps?

a) Universal Motor

b) Repulsion motor

d) Capacitor start motor

Q9. What is the function of centrifugal switch in split phase motor?

a) Protects from over current

b) Maintains constant speed

d) Make and break the starting winding from supply

Q10. What is the reason to use a permanent capacitor in fan motor circuit?

a) Speed regulation

b) Lower power consumption

c) Splitting of phase for torque

d) Controlling electrical interference

Q11. Why running winding is placed in the bottom of the core?

a) To get low resistance

b) To get low inductance

c) To get high resistance

d) To get high inductance

Q12. What is the application of shaded pole motor?

a) Hair dryer

b) Ceiling fan

c) Wet grinder

d) Washing machine

Q13. What is the function of centrifugal switch used in capacitor start, capacitor run induction motor?

a) Disconnect the running winding after reached 75% to 80% speed

b) Disconnect the starting winding after reached 75% to 80% speed

c) Disconnect the starting capacitor after reached 75% to 80% speed

d) Disconnect the starting and running winding after reached 75% to 80% speed

Q14. Where the capacitor is connected in a single phase permanent capacitor motor?

a) In series with starting winding

b) In series with running winding

c) In parallel with starting winding

d) In parallel with running winding

Q15. What is the effect, if coil group connection is wrongly connected in a single phase motor rewinding?

a) Motor runs slowly

b) Motor will not run

c) Motor runs in very high speed

d) Motor runs and takes more current at no load

Q16. How the direction of rotation of repulsion motors is to be reversed?

a) By shifting the brush-axis

b) By interchanging the supply terminals

c) By changing the main winding terminals

d) By changing the compensating winding terminals

Q17. What is the effect, if some slots in a split phase motor left out without winding after completion of concentric winding?

a) Works normally

b) Reduction in speed

c) Reduction in torque

d) Runs with very high speed

Q18. The type of the motor that does not have a commutator is:

a) Repulsion motor

b) Induction motor

c) D.C. Shunt motor

d) A.C. Series motor

Q19. The induction motors are designed for:

a) Three phases

b) Two phases

c) Single phase

d) All the above

Q20. What is the synchronous speed of 6 poles motor running at 50 hz frequency supply?

a) 1000 r.p.m.

b) 1200 r.p.m.

c) 6000 r.p.m.

d) 7200 r.p.m.

Part 1: Objective questions and answers of Single Phase Motors