P4 mid unit revision

Electrons

• All electrostatic effects are due to the movement of electrons.
• The law of electric charges states that: Like charges repel and unlike charges attract.
• When a polythene rod is rubbed with a duster, electrons are transferred making the rod negatively charged.
• Charged atoms or molecules are ions and a positive charge is caused by a lack of electrons and a negative charge by excess electrons.

Electrostatic shocks

• When inflammatory gases or vapors/high concentration of oxygen are present, a spark from static electricity can ignite these gases and cause an explosion.
• Touching something at high voltage can lead to large amounts of electric charge flowing through the body which can be fatal.
• In humans, static electricity can be a nuisance but not dangerous however, for example when a plane lands the air resistance creates static electricity as well as the friction between the tarmac and the wheels. When the oil pump is attached to the plane this can create a spark leading to an explosion. This is prevented by a earth-connected cable.
• Electric shocks can be reduced by:

- Using humidifiers/anti-static sprays/dryer cloths/moisturisers all soften materials to reduce friction and the build up of static electricity.

- Leather soled shoes/ rubber combs both are softer and so…