The Motor Effect
The motor effect is the force on a current-carrying wire in a magnetic field, which is the basis of electric motors.
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The motor effect is the force on a current-carrying wire in a magnetic field, which is the basis of electric motors.
- Use Fleming's left-hand rule
- Reverse current to reverse force
- Force is greater with a stronger field
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is The Motor Effect?
Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains The Motor Effect. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.
Check that you can explain The Motor Effect in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding The Motor Effect explains how the physical world behaves, from sport and transport to electricity and medicine.
The Motor Effect in detail
When a current-carrying wire is placed in a magnetic field, it experiences a force, the motor effect. The force is greatest when the wire is at right angles to the field, with F = BIL, where B is the magnetic flux density, I is current and L is length in the field.
Fleming's left-hand rule gives the direction: first finger for field, second for current, thumb for force (motion). Reversing either the current or the field reverses the force. The effect is the basis of electric motors, where a coil in a field turns when current passes, with a commutator reversing the current every half turn.
How the interactive helps you understand The Motor Effect
Watch the magnetic field in the interactive. Use any sliders or buttons it offers to change the values and see how the magnetic field responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of The Motor Effect.
Real-life uses and examples
- Explain everyday devices, such as brakes, lifts or chargers, using The Motor Effect.
- Use The Motor Effect to make sense of a practical and its results.
- Answer “explain” questions by linking The Motor Effect to a clear cause and effect.
Common mistakes to avoid
- Forgetting that some quantities, such as force or velocity, also have a direction.
- Mixing up The Motor Effect with a related quantity that has different units.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about The Motor Effect
What is The Motor Effect?
The motor effect is the force on a current-carrying wire in a magnetic field, which is the basis of electric motors.
What are the most important points about The Motor Effect?
The main points are: Use Fleming's left-hand rule; Reverse current to reverse force; Force is greater with a stronger field.
Why is The Motor Effect useful?
Understanding The Motor Effect explains how the physical world behaves, from sport and transport to electricity and medicine.
How can I practise The Motor Effect?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to The Motor Effect?
Related topics in Physics include Transformers, Isotopes, Nuclear Fission and Fusion.