Starter quiz
Two magnets have their poles on their large, flat faces. They are positioned as shown in the diagram. Which of the following statements about the magnetic field between them are correct?- The field line arrows point from left to right.
- The field line arrows point from right to left. ✓
- The field lines are parallel to each other. ✓
- The field lines are perpendicular to each other.
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- Which of the following diagrams show a uniform magnetic field between two magnets?
- Which of the following can be caused by moving a wire through a magnetic field?
- an induced potential and an induced current at the same time ✓
- an induced current without an induced potential
- an induced potential without an induced current ✓
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- A pupil induces a current in a coil by moving a magnet into the coil. Which of the following changes would increase the induced current?
- increasing the number of turns in the coil ✓
- moving the magnet for a longer time
- increasing the speed of the magnet ✓
- increasing the strength of the magnet ✓
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- Which of the following actions induces a potential across a wire that is in an unchanging magnetic field?
- leaving the wire stationary in the magnetic field
- moving the wire parallel to the magnetic field lines
- moving the wire perpendicular to the magnetic field lines ✓
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- A simple circuit has a resistor connected to a battery. The resistor does not heat up significantly. Which of the following statements are correct?
- The current is always in the same direction. ✓
- Current goes from the positive terminal around the circuit to the negative. ✓
- If the resistor is changed, the current in the battery changes. ✓
- If the resistor is changed, the potential difference across the battery changes.
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Exit quiz
- Current that always goes in the same direction is called ______ current.
- 'direct' ✓
- Match each key term with the correct description.
- alternator⇔A device that produces AC in a rotating coil. ✓
- motor⇔A device that makes a current-carrying coil rotate. ✓
- dynamo⇔A device that produces DC in a rotating coil. ✓
- Which of the following statements about Fleming’s right–hand rule are correct?
- The thumb represents the direction of motion. ✓
- The second finger represents the magnetic field direction.
- This rule is used to find the direction of an induced current. ✓
- This rule is used to find the direction of movement in the motor effect.
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- The diagrams show a wire loop in a magnetic field with direction shown by the grey arrow. The wire is pushed as shown by black arrows. It is part of a circuit. In which diagram is no current induced?
- Which of the following statements about a dynamo are correct?
- It produces direct current. ✓
- It produces a current that does not change.
- It can have exactly the same design as a motor, with a handle added. ✓
- Increasing the number of turns in the coil increases the induced potential. ✓
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The diagram shows an alternator’s magnets and coil (but no other parts). One side of the coil is painted orange; it is on the right, touches the left contact, and moves up. Which statement is correct?- The orange side of the coil will always be on the right.
- The orange side of the coil will always move upwards.
- The orange side of the coil will never touch the right–hand contact. ✓
- The current in the orange side will always be in the same direction.
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- Rotating a conducting loop in a uniform magnetic field induces a potential across the ends of the loop.
- An electrical generator can be made in the same way as an electric motor.
- A DC generator (dynamo) generates a varying DC current.
- The connections in an AC generator (an alternator) are different to those of a dynamo.
- An alternator makes an alternating current that repeatedly reverses direction as the coil spins round.
Common misconception
Magnets can attract or repel electric charges in a wire.
Explain that the correct explanation for what is happening is usually taught to pupils studying physics at university. At this point, it is sufficient to be able to describe and predict what happens when a conductor is moving in a magnetic field.
Keywords
Induced potential - The potential difference generated in a conductor moving relative to a magnetic field.
Direct current (dc) - An electric current that consistently flows in one direction.
Dynamo - A generator of direct current.
Alternating current (ac) - An electric current that repeatedly reverses direction.
Alternator - A generator of alternating current.
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