What is the force per unit length between two long parallel wires separated by distance d carrying currents I_1 and I_2 in the same direction?
Answer and explanation
Correct answer: A. Attractive force F/L = mu_0 I_1 I_2 / (2pid)
- Step 1: Wire 1 produces magnetic field B = mu_0 I_1 / (2pid) at wire 2. Step 2. By Lorentz force F = I_2 L B, force per unit length is mu_0 I_1 I_2 / (2pid). Using right-hand rule, like currents attract. Answer: Attractive force F/L = mu_0 I_1 I_2 / (2pid). Why not the others:* Opposite (antiparallel) currents exert a repulsive force.
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