AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Describe how the magnetic effect of a current can be demonstrated
Full specification wording
Electromagnetism: describe how the magnetic effect of a current can be demonstrated
When a current flows through a conductor, a magnetic field forms around it.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 4 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
When a current flows through a conductor, a magnetic field forms around it. This is the magnetic effect of a current. To demonstrate it, place a straight wire through a horizontal card and connect it to a battery and switch. Sprinkle iron filings on the card and tap gently; the filings form concentric circles around the wire. A plotting compass placed near the wire also shows the field direction. Reversing the battery reverses the current and reverses the field direction. Increasing the current strengthens the field, shown by a denser pattern. The same effect can be shown with a solenoid, where the field resembles a bar magnet. The demonstration therefore links current, magnetic field and direction, and shows that the effect is temporary and disappears when the current stops.
What earns the marks
- A current-carrying wire produces a magnetic field around it; the field is detected using iron filings or a plotting compass.
- Iron filings sprinkled on a card around a straight wire form concentric circles centred on the wire.
- A plotting compass near the wire aligns with the field; reversing the current reverses the compass deflection.
- Increasing the current increases the strength of the magnetic field, giving a denser or more definite pattern.
- The field disappears when the current is switched off, showing the effect is due to the current, not the wire alone.
- A solenoid carrying a current produces a field pattern similar to that of a bar magnet, with a north and south end.
Common mistakes and how to put them right
Thinking the wire itself is magnetic when no current flows.
Put it right: The magnetic field exists only while current flows.
Believing iron filings show the direction of the field.
Put it right: Filings show the shape, while a plotting compass shows direction.
Assuming reversing the current has no effect.
Put it right: Reversing the current reverses the direction of the magnetic field.
Exam tips
- Name the apparatus clearly: straight wire, card, iron filings, plotting compass, battery and switch.
- Describe the pattern as concentric circles around the wire, not just 'lines'.
- State that reversing the current reverses the field direction, and that switching off removes the field.
Try the lesson
The start of the Electromagnetism: describe how the magnetic effect of a current can be demonstrated lesson, made from checked teaching notes for this specification point.
Have a go first
Which piece of equipment is used to detect the magnetic field produced when a direct current flows through a straight wire?
Listen
When a current flows through a conductor, a magnetic field forms around it. This is the magnetic effect of a current. To demonstrate it, place a straight wire through a horizontal card and connect it to a battery and switch. Sprinkle iron filings on the card and tap gently; the filings form concentric circles around the wire. A plotting compass placed near the wire also shows the field direction. Reversing the battery reverses the current and reverses the field direction. Increasing the current strengthens the field, shown by a denser pattern. The same effect can be shown with a solenoid, where the field resembles a bar magnet. The demonstration therefore links current, magnetic field and direction, and shows that the effect is temporary and disappears when the current stops. A strong answer earns marks for these points. A current-carrying wire produces a magnetic field around it; the field is detected using iron filings or a plotting compass. Iron filings sprinkled on a card around a straight wire form concentric circles centred on the wire. A plotting compass near the wire aligns with the field; reversing the current reverses the compass deflection. Increasing the current increases the strength of the magnetic field, giving a denser or more definite pattern. A common slip: Thinking the wire itself is magnetic when no current flows. Instead, the magnetic field exists only while current flows. Exam tip: Name the apparatus clearly: straight wire, card, iron filings, plotting compass, battery and switch.
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.
Magnetic field patterns
Try answering aloud or in your head before turning the card.
Direction of magnetic field
Try answering aloud or in your head before turning the card.
Relationship between current and field strength
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 conductor, a magnetic field forms around it, and the effect is temporary and disappears when the current stops.
- Magnetic field patterns
- Iron filings sprinkled on a card around a straight wire form concentric circles centred on the wire, while a solenoid produces a field pattern similar to that of a bar magnet.
- Direction of magnetic field
- A plotting compass near the wire aligns with the field, and reversing the battery reverses the current and reverses the field direction.
- Relationship between current and field strength
- Increasing the current strengthens the field, shown by a denser pattern.
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