# Motor Effect: Lorentz Force vs Electromagnets

• Jimmy87
In summary, there is a clash of terminology when explaining why a motor rotates. One explanation involves the Lorentz force and Fleming's left hand rule, while another focuses on the current fed through the rotor causing the coils to turn into electromagnets. Both explanations are valid and may be different ways of looking at the same concept. However, the use of the Lorentz force may become more complicated when considering additional factors such as a core or permanent magnets.
Jimmy87

## Homework Statement

This is not a homework problem but more of a clash of terminology I have encountered for an explanation of why a motor rotates. In class, I have been taught about the Lorentz force causing the armature to turn. Where electrons in the wire experience a force when they experience a magnetic field at right angles to their motion. The directions of the force can be found using Fleming's left hand rule. However, I come across several explanations that do not mention the Lorentz force law or Fleming's left hand rule at all. They explain it in terms of the current fed through the rotor causes the coils in the rotor to turn into electromagnets. These electromagnets have north/south poles which try to chase the north/south poles of the magnetic stator. The video below explains this very clearly (particularly 50 seconds to 2 minutes 20). Which is the more fundamental explanation? These seem like two completely different explanations and surely only one is correct?

## The Attempt at a Solution

I'm note sure but I think they may be two ways of looking at the same thing.

Both are valid. I guess you can call the one with Lorentz force "more fundamental" if you like, but it gets more complicated to use if your coils have some core (or even permanent magnets).

Jimmy87

## What is the motor effect?

The motor effect is the phenomenon where a current-carrying conductor experiences a force when placed in a magnetic field. This force is known as the Lorentz force.

## What is the difference between the Lorentz force and an electromagnet?

The Lorentz force is the force experienced by a current-carrying conductor in a magnetic field, while an electromagnet is a device that uses electricity to create a magnetic field. The Lorentz force is one of the principles that allows electromagnets to work.

## How does the direction of the current affect the motor effect?

The direction of the current determines the direction of the Lorentz force. If the current is flowing in the same direction as the magnetic field, the force will be in one direction. If the current is flowing in the opposite direction, the force will be in the opposite direction.

## What factors affect the strength of the motor effect?

The strength of the motor effect is affected by the strength of the magnetic field, the current flowing through the conductor, and the length of the conductor in the magnetic field. The greater these factors are, the stronger the motor effect will be.

## How is the motor effect used in practical applications?

The motor effect is used in a variety of applications, including electric motors, generators, and particle accelerators. It is also used in devices such as loudspeakers, headphones, and magnetic levitation trains.

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