Electrostatics 2 Disadvantages of Static Electricity

Quick Check Conductors Materials which allow electrons pass through them. Contains free moving electrons Good conductors: metals, carbon Poor conductors: water, human body, earth

Insulators Semiconductors Electrons are tightly held to the atoms and are not free to move No free moving electrons Ex: plastics, glass, rubber, dry air Semiconductors “in-between” materials Poor conductors when cold, but much better conductors when warm. Ex: Silicon, germanium

Disadvantages of static electricity Problems associated with static: it is a nuisance when dust and dirt are attracted to insulators such as TV screens and computer monitors. it is a nuisance when clothes made from synthetic materials cling to each other and to the body, especially just after they've been in a tumble dryer Solutions: Anti-static sprays, liquids and cloths prevent the build-up of charge by allowing it to conduct away.

Dangers associated with static electricity: It is dangerous when there are flammable gases or a high concentration of oxygen. A spark could ignite the gases and cause an explosion. It is dangerous when 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. A person could die from an electric shock.

Hazards of static electricity The main danger of static electricity is in situations where a spark can cause a fire or an explosion. When oil or petrol is pumped along pipes a static charge can build up on the pipe due to friction, which could result in a spark. This could cause an explosion when the fuel vapour reacts with oxygen in the air. What is spark? an electrical discharge serving to ignite the explosive mixture in an internal combustion engine. Spark Video: https://www.youtube.com/watch?v=WWGIYd 4W5_A fuel pipe connected to earth

Antistatic floors In operating theatres it is important that the doctors to do not become statically charged when walking around. This is because some of the anaesthetic gases used are explosive. Safety Measurement: Antistatic material is used for the floor surface so that any charge is conducted to earth.

Advantages static electricity: 1. Paint spraying The spray nozzle is connected to the positive terminal of an electrostatic generator. As the paint droplets leave they repel each other and spread out to form a fine cloud of paint. The metal panel to be painted is connected to the negative terminal. The negatively charged metal panel attracts the positively charged paint.

2. Ink-jet Printer Spots of ink are given an electric charge as they leave the ink nozzle. The deflecting plates cause the drops to hit the right part of the paper. The charges on the deflecting plates change many times per second so that each drop hits the paper in a different position. Animation: https://www.youtube.com/watch?v=CFuNd3LqsIc

Online Simulations Balloons & Static Electricity - PhET - Why does a balloon stick to your sweater? Rub a balloon on a sweater, then let go of the balloon and it flies over and sticks to the sweater. View the charges in the sweater, balloons, and the wall. Electric & Magnetic Forces - 'Whys Guy' Video Clip (3:30mins) - Shows Charged Balloon & Effect of a magnet on a TV screen. John Travoltage - PhET - Make sparks fly with John Travoltage. Wiggle Johnnie's foot and he picks up charges from the carpet. Bring his hand close to the door knob and get rid of the excess charge. Fuel Ignition While Refuelling A Car - Word document with embedded video clip Charged Rod & Pith Ball - Iona Electric Force Tutorial - Science Trek How photocopying works - University of Delaware BBC KS3 Bitesize Revision: Electrical Charge BBC AQA GCSE Bitesize Revision: Attraction & Repulsion Uses of static electricity Charge, current, energy and time relationships