Page 153 - Science Coursebook

10.6 Understanding electric current

Activity 10.6
Long wires

SE Your teacher will set up a circuit with
a cell, a switch and a lamp. When the
switch is closed, the lamp lights up.

But what will happen if the connecting
wires are very, very long? Will it take a
while for the current to reach the lamp?
Will the lamp light up sooner if it is
closer to the cell?
Use what you have learnt about
electrons to decide what you think will
happen. Then test your ideas.

Lighting a lamp – current and energy
When you push a switch, a current starts immediately. + −
The electrons are waiting in the wire. They start to move
all round the circuit as soon as the switch is closed. current
energy
• The cell is the energy source for the circuit. It is a store
of chemical energy.
• The current transfers energy from the cell to the lamp.
• The lamp gets hot and shines. It is a source of light
energy and heat energy.

Question
A+I 2 A cell can make a buzzer buzz.
a Explain why the buzzer starts to buzz as soon as the circuit
is complete.
b What energy changes are happening in this circuit?

Summary
• Metals conduct electricity because they contain electrons which
are free to move.
• An electric current is a flow of charge.
• A cell pushes electrons round a circuit, transferring energy to the
components in the circuit.

10 Electricity 151