## Sunday, September 4, 2016

### Force between two infinitely straight long conductors

Let us consider two infinitely straight long conductors carrying current in the same direction.We can measure the force between the two conductors as shown below. We need to use the formula that we have derived the formula for the magnetic field at a given point using the Ampere’s law.

Basing on the magnetic field, we have derived for the force experienced by the point at a distance using the formula that was also derived.

The second conductor also carrying current and experience due to the other conductor similar to the first conductor. These forces are mutual and we can derive as shown below.

Definition of ampere

We can  define  the ampere basing on the derivation as derived earlier. If two infinitely long straight conductors carrying a certain  current separated by  unit distance experience a force of repulsion per  unit length, the current passing through each conductor is one ampere.

This is treated like a fundamental unit in the SI system  and is defined  As shown below.

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