The region around a magnet where iron or steel would be attratced.
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What does an electromagnet consist of?
An electromagnet consists of a piece of insulated wire wrapped around an iron core.
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Where are electromagnets used?
Scrapyard cranes, circuit breakers, electric bells and relays.
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What does Fleming's left hand rule stand for?
First finger = field, second finger = current and thumb = movement.
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What is the motor effect?
When we place a wire carrying an electric current in a magnetic field and it experiences force.
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What happens to the direction of the force on a wire carrying current if both the direction of current and the magnetic field are reversed?
It stays the same.
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How can the size of the force in a motor be increased?
By increasing the strength of the magnetic field or the size of the current.
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What does a split ring commutator do?
It reverses the direction of current around the coil every half turn.
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In an electric motor why does the coil spin when current is passed through it?
Because a force acts on each side of the coil due to the motor effect and because the force on one side of the coil is in the opposite direction to the force on the other side.
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What is the force if the wire is parallel to the magnetic field?
Zero.
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When is the force at its maximum?
90*
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What is electromagnetic induction?
The process of creating a potential difference using a magnetic field.
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What is increased to increase the size of the induced potential difference?
The speed of movement, the strength of the magnetic field and the number of turns on the coil.
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Why is there no potential difference induced when a bar magnet is held stationary inside a coil of wire?
The stationary bar magnet is not cutting any magnetic field lines,
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How is potential difference induced?
By cutting the lines of a magnetic field.
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What does a transformer consist of?
Two coils of insulated wire called the primary and secondary coil. They are both wound onto the same iron core.
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What does a step-up transformer do?
Makes the pd across the secondary coil greater than the pd across the primary coil.
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Why are the coils of wire insulated?
So the current doesn't short across the core or turns of wire.
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Why is the core of a transformer made of iron not copper?
Iron can be magnetised.
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How is a switch mode transformer different to a traditional transformer?
Its lighter, smaller, uses little power and operates at a much higher frequency.
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Why is a transformer used to step-up the potential difference from a power station?
So that the electrical energy can be transmitted at a high pd, reducing energy wasted in cables.
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Why are step-down transformers used?
To reduce the pd so that its safe for consumers to use.
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Why do bones show up on x-rays?
X-rays are absorbed by bones.
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Other cards in this set
Card 2
Front
What does an electromagnet consist of?
Back
An electromagnet consists of a piece of insulated wire wrapped around an iron core.
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