TOPIC 1 UNIT 1 Static electricity Friction and static electricity In this unit you will learn about:
• how friction charges atoms • how charges can attract or repel each other.
LET US CHECK ✔ All matter is made of atoms. ✔ Atoms consist of positively-charged protons, negatively-charged electrons and neutral neutrons.
New words
(electrical) charge – a store of electrical energy
friction – force caused by rubbing things together
static electricity – the build up of electric charges on an object
✔ Atoms are usually neutral and have no charge. Friction and electric charges
Have you ever noticed that your jersey sometimes sticks to your body or that your hair stands on end when you comb it on a dry day? These things happen because of electrical charges. When you rub certain materials together, they get charged with an
electrical charge. Rubbing materials together causes friction. Rub a balloon on your clothing and then put it against the wall. The balloon will stick to the wall. Friction transfers electrons from the clothing to the balloon and gives it an electric charge. The charge on the balloon makes it stick to the wall.
Materials such as plastic, perspex, glass, nylon, wool and silk can be charged by friction.
Static electricity
Static electricity is the build-up of electric charge on the surface of an object. The electric charges do not flow like in an electric circuit. The charges stay still. Static means to stay still. This is why it is called static electricity.
Friction between certain materials make electrons move from the atoms of one material to the atoms of the other material. Only electrons can be transferred to an atom or lost from an atom. The protons and neutrons do not move.
Figure 1 Electric charges make the balloon stick to the surface of the wall.
Adding electrons to an atom means there are more negatively-charged electrons than positively-charged protons. Therefore, the atom has an overall negative charge.
104 Topic 1 Static Electricity
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