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The magnetic force on a currentcarrying wire
A magnetic field will exert a force on a single moving charge, so it follows that it will
also exert a force on a current, which is a collection of moving charges.
The force experienced by a wire of length l carrying a current I in a magnetic field B
is given by
Again, the righthand rule can be used to find the direction of the force. In this case,
your thumb points in the direction of the current, your fingers point in the direction of
B. Your palm gives the direction of F.
The force between two parallel wires
Parallel wires carrying currents will exert forces on each other. One wire sets up a
magnetic field that influences the other wire, and vice versa. When the current goes
the same way in the two wires, the force is attractive. When the currents go opposite
ways, the force is repulsive. You should be able to confirm this by looking at the
magnetic field set up by one current at the location of the other wire, and by applying
the righthand rule.
Here's the approach. In the picture above, both wires carry current in the same
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This note was uploaded on 11/22/2011 for the course PHY PHY2053 taught by Professor Davidjudd during the Fall '10 term at Broward College.
 Fall '10
 DavidJudd
 Physics, Charge, Current, Force

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