Question

A square loop of wire, 5 cm on each side sits in a magnetic field of 1.2 T such that maximum flux occurs. If the loop of wire has 2 A run through it, what is the initial torque on the wire? In the problem above, the loop begins oriented so the flux through the loop is zero. What is the initial torque on the wire when the current begins?

Answer 1

In first case
`\tau =6* 10^(-3)N/m`, In second case torque = 0

Step-by-step explanation:

We have given length of the square loop = 5 cm = 0.05 m

So area
`A=side^2=0.05^2=2.5* 10^(-3)m^2`

Current through the loop = 2 A

Magnetic field B = 1.2 T

We know that expression for flux
`\Phi =BAcos\Theta`

In first case there is maximum flux so
`\Theta` must be zero

So initial torque
`\tau=IBAsin\Theta`, here B is magnetic field, I is current and
`\Theta` is angle between magnetic field and area vector.

So
`\tau=2* 1.2* 2.5* 10^(-3)cos0=6* 10^(-3)N/m`

In second case flux is zero so
`\Theta` must be 90°

So initial torque
`\tau=2* 1.2* 2.5* 10^(-3)cos90^(\circ)=0`