Page 142 - Science Coursebook

10.1 Static electricity

Science begins with observations, and then we try to explain them. So,
in this unit about electricity, we will start with some observations of
static electricity.

Perhaps you have noticed the crackling of tiny sparks when you pull off

a shirt or jumper as you go to bed. (This works best with clothes made
from synthetic materials such as nylon, and when the air is dry.) The
sparks are caused by static electricity.
Lightning is another example of static electricity, on a much larger scale.
During a thunderstorm a giant spark of electricity leaps between the
cloud and the ground.

Question
1 What do we hear after a flash of lightning?

A flash of lightning –
natural electricity.

Activity 10.1A
Observing electrical attraction

SE Here are some simple experiments you can try to find out about
static electricity. For each experiment, record what you do and what
you observe.
1 Inflate a balloon and tie the end. Rub the balloon on a woollen or

cotton cloth. Hold the balloon close to your hair. Can you feel

an effect?
2 Place some tiny pieces of paper, thread, plastic and aluminium foil on
the bench. Rub your balloon again and bring it close to the different

materials in turn. What happens?
3 Rub your balloon and touch it on the wall. Will it stick?
4 Turn on the tap so that a thin stream of water flows into the sink.

Rub a plastic rod on a cloth and bring it close to the stream of water.
Describe what you observe.

Describing static electricity
When you rub a balloon on a cloth, we say that the balloon has become charged with
static electricity. The balloon has an electric charge.

Before it has been rubbed, we say that the balloon is uncharged.
In the activity you observed that a charged object can attract other objects. Materials
such as hair, thread, paper and plastic are especially easy to attract. Metals are less
easily attracted.

Electrical attraction is an example of a force. In the next activity, you will see that
charged objects can also repel each other.

140 10 Electricity

A+I A+E