AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
The magnetic field inside a solenoid is strong and uniform.
Full specification wording
Electromagnetism: The magnetic field inside a solenoid is strong and uniform.
Inside a solenoid, away from the two ends, the field lines run parallel to the axis, evenly spaced and all pointing the same way.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 4 of 9
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Inside a solenoid, away from the two ends, the field lines run parallel to the axis, evenly spaced and all pointing the same way. That is what uniform means: the same strength and the same direction everywhere in that region. It is also a strong field, because the contributions of all the turns add there. Near the ends the lines begin to spread out, so the uniform region is the middle of the coil. This is the contrast with a bar magnet, whose field is never uniform, and it is why solenoids are used where a predictable field is needed, from relays to the magnets in a hospital scanner.
What earns the marks
- Stating that the magnetic field inside a solenoid is strong.
- Stating that the field inside is uniform, meaning the same strength and direction throughout.
- Drawing evenly spaced parallel lines inside the coil, all pointing the same way.
- Contrasting it with the field around a bar magnet, which is not uniform.
Common mistakes and how to put them right
Drawing lines inside the solenoid that curve or converge towards the centre.
Describing uniform as simply meaning all in one direction, while drawing unevenly spaced lines.
Saying the field is strong only on the axis and weak elsewhere inside the coil.
Leaving the inside of the solenoid blank when asked to draw the field pattern.
Exam tips
- Show uniform by drawing equally spaced parallel lines, with arrows all the same way.
- State both properties, strong and uniform, when a question asks about the inside of a solenoid.
- Begin the drawing inside the coil and then continue the lines round the outside.
Try the lesson
The start of the Electromagnetism: The magnetic field inside a solenoid is strong and uniform. lesson, made from checked teaching notes for this specification point.
Have a go first
Which description best matches the magnetic field inside a solenoid carrying a steady current?
Listen
Inside a solenoid, away from the two ends, the field lines run parallel to the axis, evenly spaced and all pointing the same way. That is what uniform means: the same strength and the same direction everywhere in that region. It is also a strong field, because the contributions of all the turns add there. Near the ends the lines begin to spread out, so the uniform region is the middle of the coil. This is the contrast with a bar magnet, whose field is never uniform, and it is why solenoids are used where a predictable field is needed, from relays to the magnets in a hospital scanner. A strong answer earns marks for these points. stating that the magnetic field inside a solenoid is strong. stating that the field inside is uniform, meaning the same strength and direction throughout. drawing evenly spaced parallel lines inside the coil, all pointing the same way. contrasting it with the field around a bar magnet, which is not uniform. Exam tip: Show uniform by drawing equally spaced parallel lines, with arrows all the same way.
Key words
Say what each word means before you turn the card.
uniform field
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field inside a solenoid
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parallel field lines
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comparison with a bar magnet
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See every definition
- uniform field
- A field that has the same strength and the same direction everywhere in that region.
- field inside a solenoid
- A strong and uniform field, where away from the two ends the field lines run parallel to the axis, evenly spaced and all pointing the same way.
- parallel field lines
- Lines that run parallel to the axis, evenly spaced and all pointing the same way, showing the field is uniform.
- comparison with a bar magnet
- The field inside a solenoid is uniform, whereas the field around a bar magnet is never uniform.
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