GCSE Physics Electromagnetism Question (5 Marks)

The handle of the alternator is turned, causing the coil to rotate.
Explain why an alternating current is induced in the coil
GCSE PHYSICS QUESTION.PNG

(edited 2 years ago)

Reply 1

JGLM

15

Think about the magnetic field relative to the actual coil when it has turned 180° and is upside down - lets call the left side of the coil before it moves A, and the right side the coil before it moves B. Initially, the magnetic field goes from A to B. Once the coil has rotated 180°, the magnetic field now flows from B to A. Since the direction of the field relative to the coil has changed, the induced current must also have changed direction, and this repeats as the coil continues to turn.

Reply 2

GojoSatoru822

OP

7

Original post by JGLM

Think about the magnetic field relative to the actual coil when it has turned 180° and is upside down - lets call the left side of the coil before it moves A, and the right side the coil before it moves B. Initially, the magnetic field goes from A to B. Once the coil has rotated 180°, the magnetic field now flows from B to A. Since the direction of the field relative to the coil has changed, the induced current must also have changed direction, and this repeats as the coil continues to turn.

Okay thanks for the help!

Reply 3

ertiop

5

Original post by JGLM

Think about the magnetic field relative to the actual coil when it has turned 180° and is upside down - lets call the left side of the coil before it moves A, and the right side the coil before it moves B. Initially, the magnetic field goes from A to B. Once the coil has rotated 180°, the magnetic field now flows from B to A. Since the direction of the field relative to the coil has changed, the induced current must also have changed direction, and this repeats as the coil continues to turn.

This makes sense but I wouldn't know how to phrase to get 5 marks dude
I know this is a dead thread but if anyone happens to see this message, could you please reply because I am shi*ting myself for electromagnetism.

Reply 4

username6089379

8

Original post by ertiop

This makes sense but I wouldn't know how to phrase to get 5 marks dude
I know this is a dead thread but if anyone happens to see this message, could you please reply because I am shi*ting myself for electromagnetism.

If the coil rotates, naturally, it will move, and as there is a permanent magnetic field which was created by the North and South magnet, it 'cuts' through the magnetic field lines, and this induces a PD across the coil, and (always remember) that if there is voltage across the coil, if it is in a complete circuit, a current will also be induced. The split ring commutator switches every half turn, so the P.D. also reverses direction, so every half turn the current reverses direction.

With electromagnetism questions, usually for the motor its always the first 3 points plus something more, usually being a 4 or 5 marker, therefore what my steps are:

Coil moves
Coil cuts through lines
P.D. is induced.
x
x

And these usually give you the marks, with the last two (x's) being for example as previously shown above regarding the alternating current and how the commutator allows the current to alternate between the polarities.

Hope this helped! (I am also scared about my physics paper 2 😭)

GCSE Physics Electromagnetism Question (5 Marks)

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