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6.15 starter
01 December 2011
18:08
· What’s the motor effect?
· "If there’s a magnetic field perpendicular to a current in a wire, the wire moves in a direction perpendicular to the field and the current" (FLHR)
· So what about if we move a wire in a magnetic field? What happens in the wire?
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· When we move a wire in a magnetic field, a current is induced in the wire
6.15
01 December 2011
18:08
· 6.15 recall that a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it; also recall the factors which affect the size of the induced voltage
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6.15 Practical - model answers
17 January 2012
14:33
· If you...
· Push the North pole of the magnet into the coil
A negative current flow shown by a negative deflection on the ammeter
· Keep the magnet stationary within the coil
No current
3. Pull the North pole of the magnet out of the coil
A positive current
4. Push the South pole of the magnet into the coil
A positive current
5. Push the North pole of the magnet slowly into the coil
A smaller negative current
6. Push the North pole of the magnet quickly into the coil
A larger negative current
7. Change the coil for one with more turns of wire and push the North pole of the magnet into the coil
A larger negative current
8. Push the North pole of a neodymium (strong) magnet into the coil
A larger negative current
9. Move the magnet in and out of the coil repeatedly. What sort of current is this?
An alternating current
6.15 Plenary answers
16 January 2012
· Explain carefully how you can induce a current in a wire (3 marks)
· State 3 ways you can increase the size of this induced current (3 marks)
Answers
· The wire must be perpendicular to a magnetic field
· The wire and magnetic field must move relative to each other – the wire must “cut” through the magnetic field lines/lines of magnetic flux as it moves
· A current is induced in the wire. The induced current is perpendicular to both the field and the motion
· Increase the strength of the magnets
· Increase the speed of the relative motion
· Use a coil of wire instead of a single piece of wire
