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# phya4 coils watch

1. so say if there was a coil and its connected to a battery and the coil was standing vertically.
if you drop a magnet in there face down at north pole, the coil would create a field that is in the opposite way to the field lines for the magnet. so the magnet would decelerate as it would repel. this means the force is upwards but isnt the magnetic field direction upwards too? i dont get that. the field lines represent the direction of the magnetic field doesn't it? or is that the force.

and do you use your left hand to find the current direction? im guessing not because it is dealing with electrons.
2. The magnet has its field pointing and moving downwards because the N pole is facing downwards.
The field in the coil opposes this (Lenz's Law) and points upwards as if there is a N pole at the top of the coil.
The two N-poles repel, slowing down the falling magnet.
3. (Original post by Stonebridge)
The magnet has its field pointing and moving downwards because the N pole is facing downwards.
The field in the coil opposes this (Lenz's Law) and points upwards as if there is a N pole at the top of the coil.
The two N-poles repel, slowing down the falling magnet.
so the coil makes a field that is in the opposite direction to the magnet's field, which is like upwards and curving in both directions trying to reach the bottom of the coil right? what im not understanding is when they repel, there is a force, isnt the direction of the force found by flemmings rule? if it is, then why is the force in the same direction as the field?
4. (Original post by cooldudeman)
so the coil makes a field that is in the opposite direction to the magnet's field, which is like upwards and curving in both directions trying to reach the bottom of the coil right? what im not understanding is when they repel, there is a force, isnt the direction of the force found by flemmings rule? if it is, then why is the force in the same direction as the field?
The force rule I'm referring to is just the one that says that N poles repel.
In the case of the end of a coil, the direction of the induced current is either clockwise or anti clockwise. The usual way to remember this is that if the current is clockwise, that end behaves as if it is a South Pole. If it's aNticlockwise it's a N pole.
So in your question, the current will flow anticlockwise looking down the end of the coil as the N pole of the magnet approaches it.
5. (Original post by Stonebridge)
The force rule I'm referring to is just the one that says that N poles repel.
In the case of the end of a coil, the direction of the induced current is either clockwise or anti clockwise. The usual way to remember this is that if the current is clockwise, that end behaves as if it is a South Pole. If it's aNticlockwise it's a N pole.
So in your question, the current will flow anticlockwise looking down the end of the coil as the N pole of the magnet approaches it.
ahh yeah i get the current situations now. but for the force thing, doesn't any of the flemming RH/LH rules apply? if you wanted to find the direction of the force?

or am i just worrying about something that doesn't matter, because its seems like common sense where the forces would act.
when the magnet falls faced N, the coil makes N at top and S at bottom so the magnet decelerates twice, when falling in and falling out right since S and S repel too. so two upward forces.
6. (Original post by cooldudeman)
ahh yeah i get the current situations now. but for the force thing, doesn't any of the flemming RH/LH rules apply? if you wanted to find the direction of the force?

or am i just worrying about something that doesn't matter, because its seems like common sense where the forces would act.
when the magnet falls faced N, the coil makes N at top and S at bottom so the magnet decelerates twice, when falling in and falling out right since S and S repel too. so two upward forces.
In this question you don't need to think about left or right hand rules to work out what's going to happen.
The left and right hand rules tend to be needed in cases where you have a straight wire in a field.
It's better if you post an actual exam question, as then it's possible, from the context, to see what they want.
7. (Original post by Stonebridge)
In this question you don't need to think about left or right hand rules to work out what's going to happen.
The left and right hand rules tend to be needed in cases where you have a straight wire in a field.
It's better if you post an actual exam question, as then it's possible, from the context, to see what they want.
ahh ok i get you.
thanks for the help. i was just curious about using the hand rules in this case.

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