Core Practical: Investigating Charging by Friction (Edexcel IGCSE Physics)

Aim of the Experiment

• The aim of this experiment is to investigate how insulating materials can be charged by friction

• Independent variable = Rods of different material
• Dependent variable = Charge on the rod
• Control variables:
  • Time spent rubbing the rod
  • Using the same type of cloth
  • Using the same length of rod

Equipment List

Method

Apparatus for investigating charging by friction

1. Take a polythene rod, hold it at its centre and rub both ends with a cloth
2. Suspend the rod, without touching the ends, from a stand using a cradle and nylon thread
3. Take a Perspex rod and rub it with another cloth
4. Without touching the ends of the Perspex rod bring each end of the Perspex rod up to, but without touching, each end of the polythene rod
5. Record any observations
6. Repeat for different materials

Analysis of Results

• When two insulating materials are rubbed together, electrons will pass from one insulator onto the other insulator
• A polythene rod is given a negative charge by rubbing it with the cloth
  • This is because electrons move from the cloth to the rod
  • Electrons are negatively charged hence the polythene rod becomes negatively charged

Electrons are transferred to the polythene rod whilst they move from the acetate rod

• If the material is repelled (rotates away) from the polythene rod then the materials have the same charge
• If the material is attracted to (moves towards) the polythene rod then they have opposite charges

Evaluating the Experiment

• This experiment can be carried out in several different ways
• To improve the outcome of the experiment, consider investigating a variable with a numerical result
  • For example, the independent variable could stay the same (using rods of different material)
  • The dependent variable could change to be the number of paper circles picked up by each rod

• With numerical data:
  • More analysis can be carried out e.g. creating a graph or a chart
  • Better conclusions can be drawn e.g. the rod made of ___ picked up more circles of paper than the other rods, therefore it became the most charged