Physics P3.3

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  • Created by: juddr12
  • Created on: 14-05-14 18:20

P3 3.1

The two ends of a magnet are called magnet poles: the north and the south. The area around it is called the magnetic field, which usually attacts small things like iron or steel filings. These filings form lines of force and always go north to south. 

If two magnets are pulled together, two things can happen:

  • If they are two of the same pole, they repel.
  • If they are different poles, they attract.

When a current flows through the wire, a magnetic field is created. Therefore, wrapping the wire around a piece of iron, called a core, will make it an electromagnet.

When the electricity is cut off, and the current stops flowing, the core no longer is an electromagnet. This temporary magnetism is very useful.

Electromagnets are used in cranes, circuit breakers, electric bells and relays.

P3 3.2

The motor effect is when a wire carrying electricity is in another magentic field. The force is maximum when perpendicular to the magnetic field, but is minimum when parallel to the magnetic field. 

A man named Fleming created a left-hand rule for remembering which way the wire will move. You take your left hand and point your thumb towards you, you then point you index finger to your right. Your middle finger then points downwards.

You then point your index finger in the way of the magnetic field (north to south). You point your middle finger, while keeping your index finger in the same position, pointing in the way that current moves (positive to negative). Your thumb then points in the direction of where the wire

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