Rub to charge

The idea

When objects of certain materials are rubbed together, electrical charges build up on their surfaces; these are static charges, as they cannot move by themselves, and the rubbing and rubbed objects acquire opposite kinds of charge.

A rubbed balloon

You rub a balloon with a woollen cloth.

What happens to the balloon and the cloth?

• Both get charged
• Both turn into magnets
• Nothing happens

Rub them

Press the button to rub the balloon with the cloth.

Opposite kinds

After rubbing, electrical charges had built up on both surfaces. They stay put, so they are called static charges. The balloon and the cloth got opposite kinds of charge.

When objects of certain materials are rubbed together, electrical charges build up on their surfaces. They are static charges, as they do not move by themselves. The rubbing and the rubbed objects get opposite kinds of charge.

Notes

Rubbing objects of certain materials builds up static charges on their surfaces. The two objects get opposite kinds of charge.

Check yourself

Charges that do not move by themselves are called …

When objects of certain materials are rubbed together, charges …

The balloon and the cloth rubbed against it get …

An object that has acquired static charges is called …

• static charges — correct. Yes!
• moving charges. Moving charges make a current. Static charges stay where they are.
• magnetic charges. The charges built up by rubbing are static charges.
• move away into the air. They build up on the surfaces.
• build up on their surfaces — correct. Yes!
• are never made. Rubbing makes charges build up.
• the same kind of charge. Both get charged, but with opposite kinds.
• no charge at all. Both objects get charged.
• opposite kinds of charge — correct. Yes!
• a charged object — correct. Yes!
• a magnet. A charged object has static charges. A magnet is something else.
• a neutral object. A neutral object has no charge. This one has acquired charges.