A2 physics CIE 22nd May 2013 Doubts

[TaffsAsLevel]

There's a question of paper 4 June 2009 6(b) about a horse shoe magnet, it says that the reading on the top pan balance increased by 2.3 grams. Then they ask to explain the polarity of the pole P of the magnet, isn't the force downwards because the reading increased? But mark scheme said upwards, and these kind of questions have been repeated in some years and is related to Newton's third law. Please help http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s09_qp_4.pdf

 

[victorzhaoyang]

hi, i'm glad to help you.
according to lenz's law, effect must oppose the change that producing the induced current, thus induced current must rise a force to repel your motion of the wire.
that force must be upward, and the increase in reading is due to the Newton's Third law of motion.
calculate the difference in reading rise the force hence current.
thank you!

 

[TaffsAsLevel]

hi, i'm glad to help you.
according to lenz's law, effect must oppose the change that producing the induced current, thus induced current must rise a force to repel your motion of the wire.
that force must be upward, and the increase in reading is due to the Newton's Third law of motion.
calculate the difference in reading rise the force hence current.
thank you!

But this is electromagnetism not induction?

 

[victorzhaoyang]

But this is electromagnetism not induction?

it is induction for sure.
after induction, there is electromagnetism which rise the motor effect force.
this force repel the motion of wire, just for conservation of energy. ~

 

[victorzhaoyang]

But this is electromagnetism not induction?

how was that? uh, it's midnight in China..waiting for response.

 

[TaffsAsLevel]

how was that? uh, it's midnight in China..waiting for response.

I will recheck it all on my own thanks alot