A 10.0-m-long copper wire with cross-sectional area 1.25 * 10-4 m2 is bent into a square loop, and then connected to a 0.25-V battery. The loop is then placed in a uniform magnetic field of magnitude 0.19 T. What is the maximum torque that can act on this loop? The resistivity of copper is 1.70 * 10-8 Ω·m.

Length of copper is L = 10m

Cross sectional area

A = 1.25*10^-4m²

Potential difference V = 0.25V

Magnetic field B = 0.19T

Resistivity ρ = 1.70 * 10^-8 Ω·m.

The resistance of the wire can be calculated using

R = ρL/A

R = 1.70 * 10^-8 * 10/1.25*10^-4

R = 1.36*10^-3 ohms

Using ohms law

v = IR

Then, I = V/R

I = 0.25/1.36*10^-3

I = 183.82 Amps

Maximum torque is give as

τ = NiAB

If the wire form a square

Then each side is L/4 = 10/4 = 2.5m

Then, Area of a square is L²

A = 2.5² = 6.25m²

Number of turn is assume to be 1

N=1

Therefore

τ = 1*183.82*6.25*0.19

τ = 218.29 Nm