Two long straight wires are parallel and carry current in the same direction. The currents are 8.0 and 12 A and the wires are separated by 0.40 cm. The magnetic field in tesla at a point midway between the wires is: A) 0 B) 4.0 *10^-⁴ C) 8.0 * 10^-⁴ D) 12 *10^-⁴ E) 20 * 10^-⁴

Question

Quizplus · Accepted Answer

Using the formula for the magnetic field due to a straight wire, we have:
B1 = μ0I1/(2πr)
B2 = μ0I2/(2πr)
The total magnetic field at the midpoint between the wires is the sum of the magnetic fields due to each wire:
B = B1 + B2 = μ0I1/(2πr) + μ0I2/(2πr)
B = (μ0/2πr)(I1 + I2)
B = (4π×10^-7 T·m/A)(20 A)/(0.004 m)
B ≈ 4.0×10^-4 T ≈ 0.40 mT
Therefore, the best choice is B) 4.0×10^-4 T.

Two Long Straight Wires Are Parallel and Carry Current in the Same