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# Magnets and electricity

Year 9 revision
by

## James Hudson

on 18 April 2010

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#### Transcript of Magnets and electricity

Magnets and Electricity Learning Objective:
To know what the field lines around a magnet look like.
To identify the difference between series and parallel circuits. Bar Magnets: North
Pole South
Pole Most materials are not magnetic,
but iron, cobalt and nickel are magnetic. If you bring two bar magnets together, there are two things that can happen:

if you bring a north pole and a south pole together, they attract and the magnets may stick together

if you bring two north poles together, or two south poles together, they repel and the magnets push each other away.

We say that unlike poles attract, and like poles repel.

Magnetic Fields In the diagram, note that:

the field lines have arrows on them
the field lines come out of N and go into S
the field lines are more concentrated at the poles.
The magnetic field is strongest at the poles, where the field lines are most concentrated. Electromagnets When an electric current flows in a wire it creates a magnetic field around the wire.

By winding the wire into a coil we can strengthen the magnetic field. Electromagnets are made from coils like this.
We can make an electromagnet stronger by doing these things:

wrapping the coil around an iron core

adding more turns to the coil

increasing the current flowing through the coil.
Electric current

When electric charges move in a wire, we say that an electric current flows in the wire. It's like the way a current of water flows in a river.

For an electric current to flow, we need two things:

something to make the electricity flow, such as a battery or power pack

a complete path for the current to flow in. This is called an electric circuit.

Circuit Symbols Series and Parallel Circuits The components in a circuit are joined by wires:

if there are no branches then it's a series circuit

if there are branches it's a parallel circuit

Series Circuit Parallel Circuit Thumbs up or Thumbs down If you think you could
explain the path of a magnetic field If you can explain the difference between
series and parallel circuits
Full transcript