Question

(a) Consider two parallel wires running 2 cm apart. Each wire carries a current of 10 A

running in the same direction. Sketch the set-up and calculate the magnitude

of the force per unit length between the wires. Indicate the direction of the forces

acting on the wires in your sketch.

(b) Consider that this experimental set-up was used to originally define a current of 1 A in magnitude,

i.e a current of 1 A corresponds to the current that runs through two parallel wires that experience a

force per meter of length of 2 × 10^(−7) (N / m). Why do you think physicists defined

the unit of Ampere this way rather than by counting charges moving through a wire?

Answer 1

The magnitude of force is 1.0 * 10^-3 N