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Electricity and Magnetism

Force per Unit Length between Two Long Parallel Conductors Carrying Current
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Flux density, B, near conductor 2 due to I1 is given by

So, the force which acts on length   of conductor 2 is given by

Therefore, the force per unit length is given by

Also, by Newton’s third law we can say that there is an equal but opposite force acting on conductor 1.

Now, if F/ .= 2 × 10-7 Nm-1 and r = 1m and I1 = I2, then the current in each conductor is 1 Amp.

One Amp is that current which, when flowing in each of two straight, parallel, infinitely long wires, separated by 1m, in a vacuum, produces a force per unit of 2 ×10-7Nm-1.

 

© David Hoult 2008