State the principle on which the definition of the ampere is based. - Leaving Cert Physics - Question h - 2007

The definition of the ampere is based on the principle of the force between two current-carrying conductors. Specifically, when two conductors carry an electric current, they experience a force of attraction or repulsion depending on the direction of the currents flowing through them.

This principle can be expressed mathematically as:

F = k rac{I_1 I_2}{d}

where:

• $F$ is the force between the conductors,
• $I_1$ and $I_2$ are the currents flowing through each conductor,
• $d$ is the distance between the conductors,
• and $k$ is the proportionality constant related to the nature of the medium between the conductors.