Exercise 1 Two wires with currents in them are parallel. Which directions must t

Question

Exercise 1

Two wires with currents in them are parallel. Which directions must the currents flow so the wires experience an attractive force between them? Which directions must the currents flow so the wires experience a repulsive force between them?

Exercise 2

The magnetic field strength B created by a straight wire with current I can be found from Amp`ere’s Law. 2dB = µ0I. The magnitude of the magnetic force Fb acting on a length of wire L that carries a current I will depend on its alignment angle with an external magnetic field of strength B. Fb = ILB sin Determine the equation for the magnitude of the magnetic force between two parallel currents I1 and I2 that are moving through wires of length L, and separated by a distance d.

Explanation / Answer

1)
When current is in same direction, they will experience attractive force

When current is in opposite direction, they will experience repulsive force

2)
use Ampere's law to find magnetic field due to 1 wire:
2dB = µ0I1
B = µ0*I1 / 2d

Force on other wire = B*I*L

So,
F = µ0*I1 / 2d * I2*L
= µ0*I1*I2*L/2d

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