Starter quiz
- Which of the following statements about an object made of a magnetic material are correct?
- It could be used to make a magnet. ✓
- It has a north–seeking pole and a south–seeking pole.
- It is attracted to all other objects made of magnetic material.
- It experiences a force when there is a magnet nearby. ✓
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- A pupil moves two pieces of metal towards each other and they attract each other by a magnetic force. Which of the following statements are correct?
- Both pieces could be magnets. ✓
- One piece could be a magnet and not the other. ✓
- Neither piece could be a magnet.
- Both pieces must be made of a magnetic material. ✓
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- A pupil moves two pieces of metal towards each other and they repel each other by a magnetic force. Which of the following statements are correct?
- Both pieces are magnets. ✓
- Only one piece is a magnet.
- Neither piece is a magnet.
- Both pieces are made of magnetic material. ✓
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- An electromagnet has a coil of wire wrapped around an iron core. A current flows in the wire. Which of the following statements explains why the electromagnet behaves like a magnet?
- A magnet is used to make the core.
- The wires are made of a magnetic material.
- There is a magnetic field around the current–carrying wire. ✓
- The wire gets hot, which heats the core and makes it magnetic.
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- Which of the following would decrease the strength of an electromagnet’s magnetic field?
- reducing the current in the coil ✓
- reducing the resistance of the coil
- increasing the number of turns (loops) in the coil
- replacing the iron core with a wooden core ✓
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- Which of the following statements are correct?
- An electromagnet can attract a magnet. ✓
- An electromagnet can repel another electromagnet. ✓
- Only one end of an electromagnet can pick up iron paperclips.
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Exit quiz
- Match the following key terms to their definition.
- dependent variable⇔The variable that is measured by a person doing an experiment. ✓
- control variable⇔A variable that is kept the same by a person doing an experiment. ✓
- independent variable⇔The variable that is changed by a person doing an experiment. ✓
- Which of the following statements describes a fair test?
- An experiment that has an independent variable.
- An experiment that gives accurate and reliable results.
- An experiment that gives the same results each time it is repeated.
- An experiment in which the experimenter changes only one variable. ✓
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- A pupil tests how the strength of an electromagnet’s magnetic field is affected by the current in its coil. What is the independent variable in this experiment?
- current in the coil ✓
- number of turns in the coil
- strength of the magnetic field
- material the core is made from
- number of paperclips the electromagnet can pick up
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- A pupil tests how the strength of an electromagnet’s magnetic field is affected by the current in the coil. Which of the following are control variables in this experiment?
- strength of the magnetic field
- current in the coil
- number of turns in the coil ✓
- material the core is made from ✓
- number of paperclips the electromagnet can pick up
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- Electromagnets typically have a core made of pure iron inside the coil, known as a soft iron core. What does ‘soft’ mean when describing the iron core?
- The iron is easy to bend.
- The iron is hard to bend.
- The iron remains magnetised after the current is switched off.
- The iron becomes demagnetised after the current is switched off. ✓
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- A pupil wants to make an electromagnet. They wrap bare wire around an iron core and pass a current through the wire. Why does their electromagnet not work?
- It has a very weak magnetic field. ✓
- The coils are repelled by the core.
- The coils of wire melt and stick to the core.
- Current does not go around the turns of the coil. ✓
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- The more turns of wire in the coil of an electromagnet, the stronger its magnetic field.
- The greater the current through the coil of an electromagnet, the stronger its magnetic field.
- The more closely spaced the coils of wire of an electromagnet, the stronger its magnetic field.
- An electromagnet made from bare wire will not work if adjacent turns are touching.
- A soft iron core increases the strength of an electromagnet because it becomes magnetised when it is turned on.
Common misconception
Pupils often refer to the turns of a coil as the number of coils.
Emphasise that turns of wire can be added to a coil to make the coil longer.
Keywords
Independent variable - the variable that the person doing the experiment changes
Dependent variable - the variable that the person doing the experiment measures
Control variable - the variables that may affect the dependent variable and should be kept the same
Fair test - an experiment where the control variables are kept the same
Soft iron core - the centre of a strong electromagnet that becomes magnetised
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