Page 152 - Science Coursebook

10.6 Understanding electric current

Here are some things you have learnt about electric current.

• An electric current can flow through a metal but not
through plastic.

• A cell can make a current flow round a circuit.
• The current is the same all round a series circuit.
• An electric current can light up a lamp.
We can understand this if we think about electrons, the tiny particles
which helped to explain static electricity (topic 10.3).

Question

1 Test what you remember about electrons.
a Which is bigger, an atom or an electron?
b What charge do electrons have, positive or negative?
c What charge would attract an electron, positive or negative?

at0m
Why metals conduct electricity electron
Metals are useful materials because they
contain lots of electrons which can move
about inside the metal. These electrons are not moving
tightly attached to their atoms. That is what electron

makes metals different from other materials.
A cell can make a current flow in a metal wire.

If you could look into the wire, you would see metal wire
the electrons moving along. Electrons have
an electric charge, so charge is moving
through the metal. This is what we call
an electric current. current

Electrons moving in a metal conducting electricity.
How a cell makes a current flow
Think about a cell. One end is positive (marked +), the other negative electrons
(marked −). The positive end attracts electrons (because electrons have + −
negative charge). The negative end repels electrons.
So, when a circuit is complete, the electrons in the metal of the circuit
start moving around it. They are pushed from the negative end of the
cell, and attracted towards the positive end.
Now you can see why we need a complete circuit. The electrons need to
be able to travel all the way round, from one end of the cell to the other.
Electrons move in the
That is why the current is the same all the way round the circuit. The opposite direction to
electrons don’t disappear or get used up. conventional current.

150 10 Electricity

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