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Magnetic force for Edexcel A-level Physics

Magnetic force

This page covers the following topics:

1. Attraction and repulsion, dipoles
2. Magnetic forces origin
3. Flemingโ€™s left-hand rule
4. Attraction/repulsion of nearby wires
5. Magnetic force

Magnetic forces are non-contact forces. Magnets can be attracted to or repel other magnets.

Attraction and repulsion, dipoles

Magnetic forces arise between electrically charged particles due to their motion

Magnetic forces origin

The direction of a force on a wire in a magnetic force can be found using Fleming's left-hand rule.

Flemingโ€™s left-hand rule

When two parallel wires are placed close to each other they exert a force of attraction or repulsion on each other, depending on the directions of the currents within the wire.

Attraction/repulsion of nearby wires

For a conductor at right angles to a magnetic field and carrying a current: F = BIL

Magnetic force

1

A 3m wire in a magnetic field, carrying a current of 12A, experiences a force of 5 N. What is the magnetic flux density? Give the answer to 2 d.p.

0.14

A 3m wire in a magnetic field, carrying a current of 12A, experiences a force of 5 N. What is the magnetic flux density? Give the answer to 2 d.p.

2

Fill in the gaps: Electric forces exist between stationary electric charges. Both ... and ... forces exist between moving electric charges.

electric and magnetic

Fill in the gaps: Electric forces exist between stationary electric charges. Both ... and ... forces exist between moving electric charges.

3

In Fleming's left-hand rule, the thumb points in the direction of the ...?

Movement (force)

In Fleming's left-hand rule, the thumb points in the direction of the ...?

4

Does increasing the current in the wire increase or decrease the force on a given length of wire in a magnetic field?

Increase

Does increasing the current in the wire increase or decrease the force on a given length of wire in a magnetic field?

5

A wire is in a 0.07 T magnetic field. It is carrying a current of 28 A and is 2 m long. Calculate the magnetic force on the wire.

3.92 N

A wire is in a 0.07 T magnetic field. It is carrying a current of 28 A and is 2 m long. Calculate the magnetic force on the wire.

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