REVISION NOTES
IGCSE Edexcel Physics
2.3 Energy Charge
2.3.1P Identify common materials that are electrical conductors or insulators, including metals and plastics
Conductors:
- Copper
- Aluminium
- Gold
- Silver
- Iron
Insulators:
- Glass
- Air
- Plastic
- Rubber
- Wood
2.3.2P Practical: investigate how insulating materials can be charged by friction
Apparatus needed:
- Polythene (plastic) rod
- Rods made from different insulating materials
- Multiple cloths
- Cradles
- Strings
- Wooden stands
Independent variable: Material of rod
Dependent variable: Charge of rod
Method:
- Attach the polythene rod to a wooden stand and let it hang from the string and cradle
- Attach another rod to another wooden stand and let it hang from the string and cradle
- Rub both ends of the polythene rod with a cloth
- Rub both ends of other rod with same cloth
- If the rods move towards each other they are oppositely charged
- If the rods rotate away from each other they have the same charge
Controlled variables:
- Time spent rubbing each rod
- Type of cloth
- Length of rod
- Size of cloths
2.3.3P explain how positive and negative electrostatic charges are produced on
materials by the loss and gain of electrons
Controlled variables:
- Time spent rubbing each rod
- Type of cloth
- Length of rod
- Size of cloths
2.2.4 Describe the qualitative effect of changing resistance on the current in a circuit
When an object loses electrons, it becomes positively charged
- Due to the object originally having a neutral charge
- Electrons have a negative charge
- Thus taking away negative charge from a neutrally charged object will make it positively charged
- 0 – (-1) = +1
When an object gains electrons, it will become negatively charged
- Due to the object originally having a neutral charge
- It gains negatively charged electrons
- 0 + (-1) = -1
2.3.5P Know that there are forces of attraction between unlike charges and forces of repulsion between like charges
2.3.6P Explain electrostatic phenomena in terms of the movement of electrons
- Opposite charges will attract in order to balance out
- Thus protons and electrons will be attracted to each other
- Thus objects with more protons than electrons and objects with more electrons than protons will be attracted to each other
- This is called an electrostatic force of attraction
- Sometimes electrons will travel from one material to another
- Such as from the cloth to the polythene rod
2.3.7P Explain the potential dangers of electrostatic charges, e.g. when fuelling aircraft and tankers
- When an aircraft flies through the air friction causes it to become charged with static electricity
- When the aircraft lands the electricity wants to ground itself
- This can happen as a spark or a flash of electricity
- If this happens during refuelling of the aircraft it could cause an explosion
- A solution is to earth the aircraft with a good conductor as soon as it lands
2.3.8P Explain some uses of electrostatic charges, e.g. in photocopiers and inkjet printers