# P2 Physics - Static Electricity

Topic: Static Electricty

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## Rubbing Rods

• There are 2 types off electrical charge ( postive and negative).
• Like charges repel
• Unlike charges attract
• The size of the attractive or repulsive force decreases with distance
• The electrons can be rubbed onto or off atoms
• Charge is conserved (stays the same)
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## Danger from sparks

• Clouds rubbing together produce hugh static electrical charges. These may cause lightning.
• A sweater rubbing on a shirt produces static electricity. You sometimes see and hear lots of small sparks.
• In a tv tube electrons are fired at the screen. The screen may become charged. Small sparks may then jump from the screen onto your hands.
• Large sparks such as lightning can kill people.But even quiet small sparks can be dangerous.
• A static charge can build up on a petrol tanker because of the tyres rubbing on the road. A static charge can also build up as petrol flows through a pipe.
• A metal strap is connected to the tank before the tank is opened.
• Flour is made by grinding wheat to a very fine powder.The bits of flour make the air very dusty. This mixture of the flour and air can be very dangerous. Just a tiny spark can make them explosive.
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## Making use of static electricity 2

How to remove the dirt from smoke... Smoke contains lots of tiny bits of dirt. This dirt falls on houses aand gardens. If people breathe in the dirt, it can damage their lungs:

• A metal grid and antenna are connected to the postive side of a high voltage supply.
• The metal chimney is connected to the negative side of the supply.
• Tiny bits of dirt pick up a postive charge as they pass through the grid. They are then repelled by the antenna and attracted by the chimney.
• So the sirt collects on the inside of the plates and is removed every so often.

How to make a spray hits its target...

When a liquid is sprayed out of a nozzle, it becomes electrically charged. Sprays can be made to charge the droplets as much as possible.

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