AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
When a current flows through a conducting wire a magnetic field is…
Full specification wording
Electromagnetism: When a current flows through a conducting wire a magnetic field is produced around the wire.
A current is moving charge, and moving charge always produces a magnetic field.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 1 of 9
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A current is moving charge, and moving charge always produces a magnetic field. Around a long straight wire the field lines are circles centred on the wire, lying in a plane at right angles to it, and they are closest together near the wire. The direction comes from the right hand grip rule: point the right thumb along the conventional current and the curled fingers give the direction of the field, so reversing the current reverses the field. To show the field exists, pass the wire vertically through a horizontal card. Move a plotting compass around the wire and the changing direction of the needle shows a field has been produced, or sprinkle iron filings on the card and tap it so they line up into circles.
What earns the marks
- Describing moving a plotting compass around the wire.
- Stating that the changing direction of the compass needle shows a magnetic field has been produced.
- The alternative of sprinkling iron filings onto the card and tapping it to reveal the pattern.
- Stating that the field around a straight wire is circular and reverses when the current reverses.
Common mistakes and how to put them right
Saying the wire itself becomes magnetised rather than producing a field only while a current passes.
Drawing the field lines as straight lines running along the wire.
Leaving out the tapping step, without which the iron filings do not form the pattern.
Saying the compass is attracted to the wire rather than aligning with the field.
Exam tips
- A two mark demonstration question needs the action and the observation, so write both.
- Mark the current direction on any field diagram you draw.
- Name the apparatus precisely: a plotting compass, a card, iron filings.
Try the lesson
The start of the Electromagnetism: When a current flows through a conducting wire a magnetic field is produced around the wire. lesson, made from checked teaching notes for this specification point.
Have a go first
A student switches on a circuit so that a current flows through a straight conducting wire. What is produced around the wire?
Listen
A current is moving charge, and moving charge always produces a magnetic field. Around a long straight wire the field lines are circles centred on the wire, lying in a plane at right angles to it, and they are closest together near the wire. The direction comes from the right hand grip rule: point the right thumb along the conventional current and the curled fingers give the direction of the field, so reversing the current reverses the field. To show the field exists, pass the wire vertically through a horizontal card. Move a plotting compass around the wire and the changing direction of the needle shows a field has been produced, or sprinkle iron filings on the card and tap it so they line up into circles. A strong answer earns marks for these points. describing moving a plotting compass around the wire. stating that the changing direction of the compass needle shows a magnetic field has been produced. the alternative of sprinkling iron filings onto the card and tapping it to reveal the pattern. stating that the field around a straight wire is circular and reverses when the current reverses. Exam tip: A two mark demonstration question needs the action and the observation, so write both.
See it
Key words
Say what each word means before you turn the card.
magnetic effect of a current
Try answering aloud or in your head before turning the card.
circular field around a wire
Try answering aloud or in your head before turning the card.
right hand grip rule
Try answering aloud or in your head before turning the card.
See every definition
- magnetic effect of a current
- When a current flows through a conducting wire a magnetic field is produced around the wire.
- circular field around a wire
- Around a long straight wire the field lines are circles centred on the wire, lying in a plane at right angles to it, and closest together near the wire.
- right hand grip rule
- Point the right thumb along the conventional current and the curled fingers give the direction of the field, so reversing the current reverses the field.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Electromagnetism: When a current flows through a conducting wire a magnetic field is produced around the wire.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge