Silly magnetic field question thing.

Right. Could someone give me a hint or a formula for this question?

Two power lines, each 300m in length, run parallel to each other with a separation of 35 cm. If the lines carry anti-parallel currents of 130A, what is the magnitude and direction of the magnetic force each exerts on the other?

Also, I'm really confused about all of these hand rules. Could someone list a few (as well as which finger is which) that I might need for A level?
The only one I know is the directions in F=qvB, but that's only because I remember it as

which makes things simpler...

Thanks! :suith:

Reply 1

W0nker

Not sure about that question.

But for the hand rules - it's hard to explain it in text but i'll try!

Flemmings left hand rule - hold your left hand as if in the shape a gun with your tumb pointing upwards and your first finger straight on (perpendicular to your thumb) and with your second finger, point that out to the right of your first finger (perpendicular to your first finger).

Rules are that:

thumb - motion
first finger- field
second finger - current

You can think of the field as if it was an arrow coming away from you or twoards you.

Away from you would be an X because you would see this if an arrow was firing away from you.

Towards you would be a circle with a dot in the middle because you would see this if it was coming towards you.

On diagrams in questions they might show the field with X or circles with dots in the middle to show you the direction.

Some people might rofl at this but it works perfect for me!