AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
The magnetic field around a solenoid has a similar shape to that of a bar…
Full specification wording
Electromagnetism: The magnetic field around a solenoid has a similar shape to that of a bar magnet.
Step back from a solenoid and its external field looks just like that of a bar magnet: lines emerge from one end, loop round through the surrounding space and enter the other end, so the coil…
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 5 of 9
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Step back from a solenoid and its external field looks just like that of a bar magnet: lines emerge from one end, loop round through the surrounding space and enter the other end, so the coil behaves as though it had a north pole at one end and a south pole at the other. Which end is which depends on the direction of the current around the turns, so reversing the current swaps the poles, something a bar magnet cannot do. You can find the north end with a plotting compass, or by the right hand grip rule applied to the turns. The internal and external lines join up: each line is a closed loop through the coil and back round outside.
What earns the marks
- Stating that the field outside a solenoid has the same shape as the field of a bar magnet.
- Identifying a north pole at one end of the solenoid and a south pole at the other.
- Stating that reversing the current swaps the poles.
- Drawing the external lines running from the north end round to the south end.
Common mistakes and how to put them right
Drawing the external field as circles around the coil, as though it were a straight wire.
Leaving the arrowheads off the lines outside the solenoid.
Saying the poles of a solenoid are fixed in the way a bar magnet's are.
Drawing the inside and outside lines as two separate systems that never join.
Exam tips
- Draw the parallel lines inside first, then curve them round outside to the other end.
- Label the N and S ends of the solenoid on your diagram.
- If the current direction is given, use it to decide which end is north before labelling.
Try the lesson
The start of the Electromagnetism: The magnetic field around a solenoid has a similar shape to that of a bar magnet. lesson, made from checked teaching notes for this specification point.
Have a go first
Which object has a magnetic field with the same shape as the field around a solenoid?
Listen
Step back from a solenoid and its external field looks just like that of a bar magnet: lines emerge from one end, loop round through the surrounding space and enter the other end, so the coil behaves as though it had a north pole at one end and a south pole at the other. Which end is which depends on the direction of the current around the turns, so reversing the current swaps the poles, something a bar magnet cannot do. You can find the north end with a plotting compass, or by the right hand grip rule applied to the turns. The internal and external lines join up: each line is a closed loop through the coil and back round outside. A strong answer earns marks for these points. stating that the field outside a solenoid has the same shape as the field of a bar magnet. identifying a north pole at one end of the solenoid and a south pole at the other. stating that reversing the current swaps the poles. drawing the external lines running from the north end round to the south end. Exam tip: Draw the parallel lines inside first, then curve them round outside to the other end.
Key words
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solenoid field pattern
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poles of a solenoid
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reversing the current
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closed field lines
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See every definition
- solenoid field pattern
- The field outside a solenoid has the same shape as the field of a bar magnet, with lines running from the north end round to the south end.
- poles of a solenoid
- The coil behaves as though it had a north pole at one end and a south pole at the other.
- reversing the current
- Which end is which depends on the direction of the current around the turns, so reversing the current swaps the poles.
- closed field lines
- The internal and external lines join up, so each line is a closed loop through the coil and back round outside.
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