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18 Cards in this Set
- Front
- Back
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Electromagnetic induction |
Induction of the p.d across a conductor which experiences a change in the m.g field |
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How can the speed of of simple d.c be increased |
Increase the strength of he m.g field Increase the current |
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What is a magnetic field? |
A region where magnets experience no contact force |
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What is an induced magnet |
Only gains its magnetic field when it’s in another m.g field |
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Do like poles attract or repel each other |
Repel |
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What causes this force? |
The m.g field lines of the two magnets interact with each other |
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How do we know the earths core is magnetic? |
Compass points north because of the force experienced. For the earth to hv a magnetic field it’s core must be magnetic |
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The current through a wire is increased. How does this effect the m.g field around the wire? |
Increased strength |
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What is an electromagnet? |
It’s m.g field can be switched on and off when in an electrical current |
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One use of m.g materials |
Permanent magnets in fridge doors to keep it closed |
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Explain why the bolt is pulled up across the door when the current flows through the circuit |
The current flows in the the circuit the electromagnet has a m.g field Iron bolt is magnetised and the electromagnet is attracted to it |
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Why does breaking the circuit allow the door to be opened? |
When the circuit is opened the current stops flowing through the electromagnet and it demagnetises and the iron bolt is no longer attracted to it |
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Why is a split ring commutator needed in an electric motor that uses direct current? |
Reversed the direction of the current every half turn so that force always acting in the direction that causes the coil to turn |
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How do loudspeakers use the motor effect to produce sound waves? |
Paper cone of the loudspeaker is attached to the coil of wire that sits on the pole of the permanent magnet surrounded by the other pole When the current flows through the coil a force is experienced With an a.c the force changes direction every time the current does moves b and f Which makes the air around the cone vibrate |
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Electromagnet induction |
P.d is created across a conductor which is experiencing a change in the m.g field |
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How can can electromagnet induction be used to generate a p.d across a coil of wire? |
Move the coil of wire in and out a magnetic field Move external m.g field around the coil of wire |
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Earphones |
When the a.c flows through the coil of wire the m.g field of the permanent magnet force is exerted on it Which causes a movement The a.c constantly changes direction which causes the direction of the force to do this also- vibrates back and forth Causes pressure vibrations |
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What are transformers used for in the national grid |
The increase the voltage but decrease the current as that reduces the amount of energy lost Decrease the current to safe levels before it reaches users |
