Starter quiz
- Which of the following metals are magnetic?
- iron ✓
- sodium
- cobalt ✓
- copper
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- Which statement about the magnetic field lines round a bar magnet is correct?
- They point out of both the N–pole and the S–pole.
- They point into both the N–pole and the S–pole.
- They point out of the N–pole and into the S–pole. ✓
- They point out of the S–pole and into the N–pole.
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- Earth's magnetic field behaves as if there is a magnet inside the planet. Which of the following statements about this imaginary magnet is correct?
- The S–pole of the magnet is at Earth's North Pole. ✓
- The S–pole of the magnet is at Earth's South Pole.
- The S–pole of the magnet is at Earth's equator.
- The N–pole of the magnet is at Earth's equator.
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- Where is Earth's magnetic field strongest?
- at the equator
- at the north and south poles ✓
- at the Bermuda triangle
- on top of the highest mountain
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- Which of the following will not deflect a magnetic compass needle?
- an iron nail
- a steel fork
- a nickel coin
- an electrostatically charged balloon ✓
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- Which of the following statements about the poles of magnets is correct?
- A north pole will attract a north pole.
- A north pole will attract a south pole. ✓
- A north pole will repel a south pole.
- A south pole will attract a south pole.
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Exit quiz
- Which of the following would not cause a compass needle to deflect?
- an electrostatically charged plastic ruler ✓
- a copper wire carrying current
- Earth's magnetic field
- an iron rod
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- Which of the following is not needed to make a strong electromagnet?
- an iron rod
- insulated wire
- a power supply
- paperclips ✓
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Why do paper clips fall off the electromagnet when the current is turned off?- The magnetism has returned to the power pack.
- There is no current in the coil. ✓
- The wire has overheated.
- The paperclips repel the core.
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- Which of the following changes will not make an electromagnet stronger?
- Increasing the current in the wire.
- Increasing the voltage across the wire.
- Increasing the number of turns in the coil.
- Increasing the number of paperclips. ✓
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- Which of the following will increase the strength of the magnetic field in a coil of insulated wire?
- Increasing the diameter of the coil.
- Increasing the resistance of the wire in the coil.
- Putting an iron core in the coil. ✓
- Putting a copper core in the coil.
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- What is the shape of the magnetic field lines caused by a straight, current–carrying wire?
- spherical around the wire
- straight and away from the wire
- circular around the wire ✓
- straight and in the same direction as the wire
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- When there is an electric current in a wire, there is a magnetic field around the wire.
- When there is an electric current in a coil of wire, the magnetic field around each loop adds to make a stronger field.
- An electromagnet is made by wrapping a coil of wire around a core.
- An electromagnet is a magnet that can be turned on with an electric current, and turned off.
Common misconception
A magnetic field is the same as the electric field around a charged object.
Demonstrate that a balloon with a static electric charge does not affect the magnet in a plotting compass.
Keywords
Magnetic field - this exerts a force on magnets and magnetic materials
Coil - a wire wound round in loops and looks like a spring
Core - the centre of an electromagnet around which a wire is wound to make a coil
Turn - a single loop of wire in a coil
Electromagnet - a magnet made using a coil, a core and a power supply
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