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24 Cards in this Set
- Front
- Back
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What is a magnetic field? |
The area around a magnet in which another magnet would feel a force. |
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What do magnetic field lines show? |
-Direction of field lines (north to south) -Strength of magnetic field (stronger at poles) -Shape of magnetic field |
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What happens if you break a magnet? |
Two new magnets are produced. |
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What are the differences between soft and hard magnetic materials? |
Soft magnetic materials are easy to induce magnetism on but lose magnetism easily afterwards. |
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What are the magnetic materials? |
Nickel, cobalt and iron (and steel) |
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What is magnetic induction? |
When a magnetic material is close to another magnet and becomes a magnet itself. |
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What is an electromagnet? |
A magnet in which the magnetic field is produced by an electric current. |
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How do you know the directions of the electric current and magnetic fields in an electromagnet? |
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Electromagnets can be made stronger by... |
-Increasing the number of coils -Increasing the current -Using a stronger magnetic core |
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What is a solenoid? |
A cylindrical coil of wire acting as a magnet when carrying an electric current. Lots of coils around a core, creating a strong electromagnet. |
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If the coils of a solenoid are anticlockwise, what is the polarity of the solenoid? What happens if the direction of current is reversed? |
North Then the polarity changes. |
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Explain how motors work. |
-magnetic field forms around the coil -magnetic field interacts with permanent magnetic field -coil experiences a force which causes it to turn -split ring commutators reverse the direction of current so the direction of the motor is the same |
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When is the force greatest? |
When the wire is perpendicular to the magnetic field. |
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How can the direction of a wire be determined? |
Fleming's left hand rule |
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What kind of current do electric motors have? |
Direct current |
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What is electromagnetic induction? |
When a magnet if moved inside a coil and an electric current is induced (because the coil cuts through the magnetic field lines). |
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How do you create a stronger current? |
-Move the magnet faster -Use a stronger magnet -More coils |
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Electromagnetic induction is how generators work. What kind of current do generators have? |
alternate current |
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What can be calculated using Fleming's right hand rule? |
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What is the function of a transformer? |
To change the voltage of A.C. currents. |
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How do generators work?
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-electric current is induced because the magnetic field around the coil is changing -alternating current produced |
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How do transformers work? |
-this current is AC so the magnetic field is changing -the secondary coil experiences a changing magnetic field -so a current is induced in the secondary coil |
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Why do we need transformers? |
-the power stays the same, but the voltage is increased and the current is decreased (power = voltage x current) -the decreased current means less energy is lost through heat, especially when travelling over long distances |
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What is the equation for transformers?
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Voltage primary / voltage secondary = no. of turns primary / no. of turns secondary |
