P4a - Sparks

P4a - Sparks

1. Static electricity

   • Conductors and Insulators
     • Metals are good conductors, which means that electric charges move easily through them.
     • Materials such as plastic, wood, glass and polythene are insulators, this means they don't allow electric charges to move through them.
     • Some insulators can become electrically charged when they're rubbed together.
   • How can you tell if an insulator is charged?
     • If a plastic rod is rubbed with a duster it attracts small pieces of paper
     • When a balloon is rubbed on a jumper it can stick to a wall.

2. Positive & Negative charges

   • Objects can be positively charged, negatively charged or neutral (no charge).
   • A substance that gains electrons becomes negatively charged, while a substance that loses electrons becomes positively charged.
   • When an acetate rod is rubbed with a duster, electrons are transferred from the rod onto the duster, making the rod positively charged.
   • Atoms or molecules that become charged are ions.

3. Electric shocks

   • You can get an electrostatic shock from charged objects, such as clothing made from nylon.
   • You can get an electrostatic shock if you are charged & you touch something that is earthed.
   • Problems with static electricity
     • Dust and dirt is attracted to insulators such as TV screens and computer monitors
     • Clothes made from synthetic materials often cling to each other and to the body, especially just after they've been in a tumble drier.
     • There are flammable gases or vapours or a high concentration of oxygen. A spark could ignite the gases and cause an explosion
     • You touch something with a large electric charge on it. The charge will flow through your body causing an electric shock. This could cause burns or even stop your heart.

4. Safety measures

   • The chance of receiving an electric shock can be reduced if:
     • An object that might become charged is earthed by an earth wire, so any charge immediately flows down the earth wire
     • In a factory, machinery operators stand on insulating mats or wear shoes with insulating soles. Stopping any charge flowing through them to earth.
     • Lorries containing flammable gases, liquids and powders are earthed by an earth wire before being unloaded. Charge immediately flows down the earth wire preventing a spark/ explosion.
   • Anti-static sprays, liquids and cloths prevent the build-up of charge by allowing it to conduct away.