AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Draw the magnetic field pattern for a straight wire carrying a current and…
Full specification wording
Electromagnetism: draw the magnetic field pattern for a straight wire carrying a current and for a solenoid (showing the direction of the field)
A straight current-carrying wire has a magnetic field made of concentric circles centred on the wire.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 5 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A straight current-carrying wire has a magnetic field made of concentric circles centred on the wire. The circles lie in planes perpendicular to the wire. To show direction, use the right-hand grip rule: point the thumb of your right hand along the conventional current, and your curled fingers show the field direction. For a solenoid, the field lines outside resemble those of a bar magnet, running from the north end to the south end, while inside the solenoid the field lines are parallel and close together, running from south to north. The ends behave as north and south poles. Reversing the current reverses the field direction. When drawing, use arrows on the field lines, keep the lines smooth and non-crossing, and show the wire or solenoid clearly.
What earns the marks
- For a straight wire, draw concentric circles centred on the wire, with arrows showing the field direction.
- Use the right-hand grip rule: thumb along conventional current, curled fingers give the field direction.
- For a solenoid, draw field lines outside running from the north end to the south end, like a bar magnet.
- Inside the solenoid, draw field lines parallel to the axis, running from south to north, with arrows.
- Mark the ends of the solenoid as north and south poles, and reverse them if the current is reversed.
- Ensure field lines are smooth, do not cross, and include arrows to show direction.
Common mistakes and how to put them right
Drawing straight radial lines around a straight wire instead of concentric circles.
Put it right: The field lines are circles centred on the wire.
Omitting arrows on field lines.
Put it right: Arrows are needed to show the direction of the field.
Drawing the field inside a solenoid running from north to south.
Put it right: Inside the solenoid the field runs from south to north.
Exam tips
- Use a sharp pencil and a compass or circular object to draw neat concentric circles for the straight wire.
- Label the current direction and use the right-hand grip rule to check your arrows.
- For the solenoid, draw the external field like a bar magnet and add parallel internal lines with arrows.
Try the lesson
The start of the Electromagnetism: draw the magnetic field pattern for a straight wire carrying a current and for a solenoid (showing the direction of the field) lesson, made from checked teaching notes for this specification point.
Have a go first
Which description correctly identifies the shape of the magnetic field pattern around a straight wire carrying a steady current?
Listen
A straight current-carrying wire has a magnetic field made of concentric circles centred on the wire. The circles lie in planes perpendicular to the wire. To show direction, use the right-hand grip rule: point the thumb of your right hand along the conventional current, and your curled fingers show the field direction. For a solenoid, the field lines outside resemble those of a bar magnet, running from the north end to the south end, while inside the solenoid the field lines are parallel and close together, running from south to north. The ends behave as north and south poles. Reversing the current reverses the field direction. When drawing, use arrows on the field lines, keep the lines smooth and non-crossing, and show the wire or solenoid clearly. A strong answer earns marks for these points. For a straight wire, draw concentric circles centred on the wire, with arrows showing the field direction. Use the right-hand grip rule: thumb along conventional current, curled fingers give the field direction. For a solenoid, draw field lines outside running from the north end to the south end, like a bar magnet. Inside the solenoid, draw field lines parallel to the axis, running from south to north, with arrows. A common slip: Drawing straight radial lines around a straight wire instead of concentric circles. Instead, the field lines are circles centred on the wire. Exam tip: Use a sharp pencil and a compass or circular object to draw neat concentric circles for the straight wire.
Key words
Say what each word means before you turn the card.
Magnetic field patterns
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Direction of magnetic field
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Right-hand grip rule
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Solenoid as an electromagnet
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See every definition
- Magnetic field patterns
- For a straight wire, concentric circles centred on the wire; for a solenoid, lines outside like a bar magnet and parallel lines inside.
- Direction of magnetic field
- Shown by arrows on the field lines, with the field reversed when the current is reversed.
- Right-hand grip rule
- Point the thumb of your right hand along the conventional current, and your curled fingers show the field direction.
- Solenoid as an electromagnet
- The ends behave as north and south poles, with field lines outside running from the north end to the south end.
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