Question

The hot and neutral wires supplying DC power to a light-rail commuter train carry 700 A and are separated by 70.0 cm. What is the magnitude (in N) of the force between 30.0 m of these wires?

Answer 1

4.197 N

Step-by-step explanation:

current through the wires I = 700 A

distance between wires r = 70 cm = 0.7 m

length of each wire L = 30 m

force per unit length on the wires is given as

`(F)/(L)` =
`(u*I^(2) )/(2\pi r )`

where u = permeability of vacuum = 1.256
`10^(-6)` m-kg-
`s^(-2)`
`A^(-2)`

F =
`(u*I^(2)L )/(2\pi r )`

F =
`(1.256*10^(-6) *700^(2)*30 )/(2*3.142*0.7 )` = 4.197 N