The Student Room Group

A2

(edited 7 years ago)
Reply 1
Ahh okay this did help thanks
Reply 2
Okay i need help on q7 again, whats l?
Reply 3
(edited 7 years ago)


For question 15, draw a free-body diagram to "see" what are the forces acting on the charge. Remember that weight is always pointing downward.

Then make use of Newton's second law to solve for the magnitude of the electric field strength. You need to make use of the charge-to-mass ratio.

For question 20, take a look at this video to see if you can explain what is going on.
https://www.youtube.com/watch?v=9fhVn4YgwB8

When the switch is closed, the current in the wire would give rise to a magnetic field and the interaction of the two magnetic fields results in a magnetic force acting on the wire. According to the Newton's third law, a magnetic force would act on the magnet due to the wire, which is the reading of 161 g. (I did not state the direction of the force - I hope you can figure it out or else reply to ask for help).

Remember the question ask when the current is reversed and doubled......

I did not give the full solutions but I hope the hints are enough for you work out the answer.

Quick Reply

Latest