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 length of rope approx 3m – ideally made of nylon
• 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. Avoid rope burns by ensuring students don’t grip the rope too tightly.

## Procedure

1. Set up or draw a diagram of a series circuit with one cell and one bulb. Explain that you will be modelling it using a rope loop.
2. Ask a student volunteer to grip the rope lightly with one hand so that it can slip through easily. They represent the light bulb in the circuit.
3. Hold the opposite end of the rope loop and make it circulate by pulling it at a steady rate, hand over hand. You, the teacher, are like the cell. The moving rope is like the current.

## Discussion prompts

• Where did the ‘current’ start flowing first?
• How does the current in and out of the bulb/battery compare?
• How can I make the current bigger?

## Teaching notes

Students often think that the charges in a circuit must travel from the cell to bulb in order for a bulb to light. Use this activity to emphasise there is no (perceptible) delay between a circuit being switched on and a bulb going on. Charges in the circuit all start moving at the same time and the rate of flow is the same throughout. Link friction to electrical resistance. How quickly the rope moves depend on the size of the resistance and how large the ‘push’ (voltage) provided by you is.

For a more detailed discussion of how to incorporate this model into a teaching approach see our modelling electrical loops collection.

## Learning outcome

Students describe current as a flow that happens throughout a circuit.

This experiment was safety-checked in March 2020.