Electromagnetism

Question 1

1. In a speaker, there is a current carrying coil
2. This coil has a magnetic field around it
3. This magnetic field INTERACTS with the magnets magnetic field
4. Due to LHR there is a force on the coil
5. The coil is attached to the cone - therefore the cone moves in one direction

If the current in a speaker is a.c, describe the movement of the coil and cone and how this creates a sound wave.

Answer 1

1. Alternating current means the current in the coil changes direction continuously.
2. This means the force on the coil/cone changes direction continuously - cone moves in and out (vibrates)
3. This creates a sound wave (compression wave) in front of the cone at the same frequency as the alternating current.

Question 2

Describe the left hand rule (LHR)

Answer 2

First Finger - Field

Second Finger - Current

Thumb - Movement

Question 3

Use the LHR to explain why the wire moves to the left.

Answer 3

1. Current carrying wire (seCond finger- CURRENT)
2. 90º to magnetic field (First finger field)
3. Using LHR this creates a force to the left- wire moves left (thuMb movement)

Question 4

How do we use dot and crosses to represent the direction of a magnetic field or current?

Answer 4

dot means out of the page

cross means into the page

Question 5

What happens to the direction of the magnetic field around a wire if the direction of the current it reversed?

Answer 5

The direction of the magnetic field is reversed.

Question 6

Define a magnetic field

Answer 6

A region of space where a magnetic material experiences a force

Question 7

A wire with a current running through it produces a…..

Answer 7

magnetic field around it

Question 8

How can you increase the force acting on a current-carrying wire in a magnetic field

Answer 8

• increase current
  -stronger magnets
• more turns of wire