The force per meter between the two wires of a jumper cable being used to start a stalled car is 0.244 N/m. (a) What is the current (in A) in the wires, given they are separated by 1.70 cm

Answer: current I is 144amp (A)

Explanation: The force per lenght F/L, current l, and separation distance r are related by the formula

F/L = permeability of space * I²/2*pi*r

Permeability of free space is 1.257*EXP {-6} Henry/meter

F/L is 0.244 N/m, pi is 3.142,

r is 1.7cm which is equal to 0.017meter.

I is what we are looking for.

Now we have after substitution,

0.244

= 1.257*EXP {-6} * I² / (2*3.142*0.017)

After cross multiplying and making I² subject of formula we have,

0.0261 / (1.257*EXP {-6}) = I²

I = √{20736.7} = 144ampere (A)

That means in each of the jumper wire there is 144amp (A)