Electrodynamics

Question 1

What is electrodynamics the study of?

Answer 1

It is the study of energy conversion from electrical energy to mechanical energy

Question 2

What is the basic principle of electrodynamics?

Answer 2

When a conductor carries a current and is placed in a magnetic field perpendicularly, it will experience a mechanical force

Question 3

How do we determine the direction in which the conductor moves?

Answer 3

By using Flemings left hand rule. (thumb=direction, pointy finger=field direction, middle finger=current direction)

Question 4

What are the factors affecting magnitude of force?

Answer 4

1) Increases with magnitude of current
2) Increases with strength of magnetic field
3) Increases with length of wire

Question 5

What is the function of electric motor?

Answer 5

It is a machine which converts electrical energy into mechanical energy

Question 6

Principle of an electric motor

Answer 6

1) When a current flows in the circuit, one side will experience an upward force while the other side experiences a downward force. Since the two forces are equal and in opposite directions, the coil rotates in a clockwise direction.
2) When the coil is in a vertical position, a gap will be left between the carbon brushes, the coil does not stop because the initial turning effect makes it move past its vertical position.
3) When the coil moves past its vertical position, the commutator changes the direction of the current so it is reversed. The coil rotates continuously in the same direction

Question 7

Why do we use a rectangular coil and not a straight wire?

Answer 7

To produce a turning effect

Question 8

What is the purpose of the commutator?

Answer 8

It reverses the direction of current each time it moves past its vertical position hence maintaining a continuous rotation of the coil

Question 9

What is the purpose of the carbon brushes?

Answer 9

It provides electrical contact between the rectangular coil and external circuit

Question 10

Factors affecting the turning effect of the coil

Answer 10

1) It increases with current
2) It increases with strength of magnetic field
3) It increases with area of coil
4) It increases with number of turns in the coil

Question 11

Why is the efficiency is less than 1?

Answer 11

Power is lost in the system due to power needed to overcome air resistance and lost in the form of heat