The motor effect
I can describe the force acting on a current–carrying wire or loop in a uniform magnetic field.
The motor effect
I can describe the force acting on a current–carrying wire or loop in a uniform magnetic field.
Lesson details
Key learning points
- The magnetic field lines around a current-carrying wire are concentric circles
- In a uniform magnetic field, a current carrying wire is forced in one direction
- Fleming’s left–hand rule can be used to predict the direction of movement of a current–carrying wire in a magnetic field
- The force on a current–carrying conductor at right angles to a magnetic field, $$F$$, is found using $$F = B I l$$
- Opposite sides of a conducting coil in a uniform magnetic field are forced to move in opposite directions
Keywords
Uniform magnetic field - has evenly spaced field lines and the strength of the magnetic field is the same everywhere
Fleming’s left-hand rule - indicates the direction a conducting wire is forced to move in a uniform magnetic field
Magnetic flux density, B - is a measure of the strength of a magnetic field
Tesla (T) - is the unit that magnetic flux density is measured in
Common misconception
It is not clear how the magnetic field around a conducting wire interacts with a uniform magnetic field.
Focus on observing and predicting the direction that a conducting wire is forced in by a uniform magnetic field, and openly admit that explaining this in terms of how the magnetic field interact is too challenging to include in the syllabus.
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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Starter quiz
6 Questions
Exit quiz
6 Questions
first finger -
represents the magnetic field direction
second finger -
represents the direction of the current in the wire
third finger -
is not used in Fleming’s left-hand rule
thumb -
represents the direction of the force on the wire
side P -
An upwards force acts.
side Q -
No force acts.
side R -
A downwards force acts.