Electric Current
Electricity and Magnetism

# Rope loop circuit

Practical Activity for 11-14

In this activity students observe a rope loop being circulated. You can use it as a model to introduce circuits.

## Equipment

• A 3 m length of rope - preferably made of nylon with speckles (alternatively draw dots on a normal rope with marker pen)
• Duct tape (optional)
• Leads, a cell and a bulb (optional)

## Preparation & safety

Tie the rope into a loop, or if you are using a nylon rope melt the ends together then cover the join with duct tape.

## Procedure

1. Set up or draw a diagram of a series circuit with one cell and one bulb.
2. Show the class the rope loop and explain that that the dots on the loop represent charged particles (electrons) in the circuit.
3. Ask a student volunteer to lightly grip the rope with one hand so that it can slip through easily. They will be representing the light bulb in the circuit
4. Hold the opposite end of the loop and check your volunteer isn’t gripping too tightly (to avoid rope burns)
5. Circulate the rope by pulling it at a steady rate, hand over hand. You, the teacher represent the cell, and the speed of the moving speckles/dots show the size of the current.

## Discussion prompts

• Where did the 'current' start flowing first?
• How does the current entering and leaving the bulb/battery compare?
• How can I increase the current?

## Teaching notes

Many students believe that electrons must travel from the cell to the bulb in order for a lighting circuit to work. Some also think that current gets used up in a circuit. Emphasise that the speckles/dots (electrons) in this model all start moving at the same time and flow in a continuous loop.

Another common misconception is that a cell will provide the same current irrespective of the circuit it is placed in. Discuss or demonstrate how the speed of the dots (current) increases if you increase the size of the push (voltage) or your volunteer decreases friction (resistance).

## Learning outcome

Students describe current as a flow that happens throughout a circuit that’s size depends on voltage provided by a cell and resistance of the component(s).

This experiment was safety-checked in March 2020.