few q's

[fredrick]

q1)two current carrying conductors are placed parallel as shown. what is the direction of the net force on point X.
[IMG]http://img232.imageshack.us/img232/62/q1mw3.th.png[/img][IMG]http://img232.imageshack.us/images/thpix.gif[/img]

q2)when a bar magnet moves into a coil as shown, desbribe what happens in terms of induced current when the bar enter and then leaves the solenoid out the other end.
[IMG]http://img139.imageshack.us/img139/7051/q2by8.th.png[/img][IMG]http://img139.imageshack.us/images/thpix.gif[/img]

[Collin Li]

Question 1

Use right hand grip rule (on the top wire) to figure out the magnetic field that is in the vincinity of X (into the page).

Now, using that as the magnetic field, use the right hand slap rule (at point X) to figure out the force (up).

Question 2

Firstly, it will experience a change in flux, coming into the coil. By Lenz' law this will cause a current that would oppose this change in flux (around the circuit from Y to X).

As the bar leaves, it will experience a change in flux, leaving the coil. By Lenz' law this will cause a current that would opposte this change in flux (around the circuit form X to Y).

In the middle, you can either say that there is no change in flux (no current induced), or the change in flux gradually approaches zero as it gets to the centre of the coil.