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Magnetic Force on a Wire

Student 5051 9 years ago updated by Physics Tutorial Center Staff 9 years ago 1

The magnetic force on a wire I understand to be dF = I dl x B. However, is this assuming the magnetic field and current is constant. If neither of them are, doesn't that mean you would need to apply the product rule?


Thank you

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The formula you provided is a differential, meaning you're finding the force dF on a small piece of wire dl. This bit of wire is infinitesimally small, so B and I are essentially constant.


If B is not constant then you will need to take an integral over the path of the wire. In general this is not what we do to solve problems, though, so usually you use F = I L x B for a straight piece of wire L and constant B

Answer
Closed

The formula you provided is a differential, meaning you're finding the force dF on a small piece of wire dl. This bit of wire is infinitesimally small, so B and I are essentially constant.


If B is not constant then you will need to take an integral over the path of the wire. In general this is not what we do to solve problems, though, so usually you use F = I L x B for a straight piece of wire L and constant B