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Hi, I'm confused about the formula to find the magnetic force exerted on a current by a magnet, given by the formula F = number of wires (n) * current in each wire (I) * length of wire (l) * strength of magnetic field (B) so: F = nIlB

It also says that only the component of the magnetic field that is perpendicular to the current causes the force.

So I was wondering, the book says the l value changes depending on the location of a magnet, so if the wire is 8cm long and the field is perpendicular (and I assume 8cm long?) the l value is 8*10^-2m. However if the wire is parrellel to the field then the l value is 0. So I'm abit confused as to what the l means. So how does l change if the field is at an angle to the wire, can it be? Like if it's at an angle of 30 degrees to the wire does that mean I have to multiply the value of l by sin30 to get the verticle component? Or is the books definition of l abit loose and does it refer to like the length of the wire in the field? But how does this relate if the field is at an angle?

Sorry if my questions are confused, I'm very confused myself :( Thanks!

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# Homework Help: Force of a magnetic field on a current

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