Further Applications of electromagnetism

Question 1

What is an AC motor?

Answer 1

A motor that runs on alternating current.

Question 2

What is a generator?

Answer 2

A generator converts rotational kinetic energy into electrical potential energy. (does the opp. to a motor)

Question 3

What is the main difference in an AC generator?

Answer 3

Slip Rings maintain a constant connection between the rotating coil and the circuit
- induced emf alternates every half turn of the coil
more reliable and less maintenance

Question 4

What is the main feature of a DC Generator?

Answer 4

Split Ring Commutator - reverses the connections between the coil and external circuit every 180 degrees. Induced EMF alternates every half turn of the coil

Question 5

What is an AC induction motor?

Answer 5

Consists of a stator and rotor - AC power source
- 120 degrees out of phase
- Consists of a squirrel cage rotor - mounted on a soft laminated iron core armature

Question 6

Describe what a DC motor is

Answer 6

1. Source of Emf - current through the coil
2. Armature - coil rotates within the external B field - supplied by permanent magnets
3. Split Ring Commutator - maximum value = 1 - torque falls to zero - automatically switches to current
4. Brushes maintain electrical contact between commutator and circuit

Question 7

Explain what back EMF is

Answer 7

Back EMF is induced emf that acts in the opposite direction to the supply emf

Question 8

Change in flux =

Answer 8

Induced EMF by Lenz’s law which will be opposite to the direction of the supply emf