Question

An electric bus operates by drawing current from two parallel overhead cables, at a potential difference of 600 V, and spaced 53 cm apart.

1. When the power input to the bus’s motor is at its maximum power of 90 hp , what current does it draw?

2. When the power input to the bus’s motor is at its maximum power of 90 hp , what is the attractive force per unit length between the cables?

Answer 1

P = 90 hp = 67113 w I = P/V = 11.855 A I TildeEqual 111.86 A B = mu.I/2 pi r F = BIL F/L = BI = mu.I^2/2 pi r Force per unit length = mu_0 I^2/2 pi r = 4 pi times 10^-7 times (111.86)^2/(2 pi) (0.35) = 4.72 times 10^-3 (N/m)