4.1 Electrical ChargesApril 20, 2023

•Opposite charges attract

•Same charge repels.

•Insulating materials that lose electrons become positively charged.

•Gaining electrons makes an object negative.

Van de Graaff generator

Over 100,000 Volts!

Crackling noises when taking off some clothes is caused by many tiny sparks.

Static experiments

• Rub a polythene (White) rod with a cloth.

1. Hold the rod near some dry paper.2. Hold the rod near a stream of

gently running water.3. Hold the rod near someone’s hair.

•Rub an acetate (clear) rod with a cloth.

Repeat the above experiments. Explain why this happens.

Charging by friction

+ - + - + - + - + - + - + - + - + - + -

Uncharged – equal numbers of protons and electrons

Polythene

+ - + - + - + - + - + - + - + - + - + -

- - -

- - - -

After rubbing

rod cloth+ + + + + + +

Gains electrons making it __________. Loses electrons making it __________.

Perspex becomes positively charged after rubbing. Explain why.

Van de Graaff GeneratorA VdG collects large amounts of charge on the dome.

At the bottom is an acetate roller and at the top a polythene one. How do you think charge reaches the top?

AQA Additional Science

• 21.25%• PSA B2 Biology 45 min exam May 08

25%• C2 Chemistry 45 min exam Jun 08

25%• P2 Physics 45 min exam Jun 08 25%• Additional ISA 3.75%

PSA - Practical Skills Assessment2 Marks •Work is carried out SAFELY but

sometimes lacks a good method.•Apparatus used with help.

4 Marks •Work is SAFE and reasonably organised.•Apparatus used with skill without help.

6 Marks •Work is safe and well organised.•A range of difficult apparatus used with skill.•All measurements taken accurately.•Present data in a suitable table