Core Practical 3: Investigating Charging by Friction
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
- Take a polythene rod, hold it at its centre and rub both ends with a cloth
- Suspend the rod, without touching the ends, from a stand using a cradle and nylon thread
- Take a Perspex rod and rub it with another cloth
- 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
- Record any observations
- 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