Five very long, straight insulated wires are closely bound together to form a small cable. Currents carried by the wires are: `I_1=20A, I_2=-6A, I_3=12A, I_4=-7A, I_5=18A`. (Negative currents are opposite in direction to the positive.) The magnetic field induction at a distance of 10cm from the cable is (current enters at A and leaves at B and C as shown)

Options

A. `34 muT`
B. `74 mT`
C. `34 mT`
D. `74 muT`

Answer

D

Explanation

`i_(net) = 20 - 6 + 12 - 7 + 18 = 37A`
`B = (mu_(0))/(4pi), (2i)/(a) = 10^(-7) xx (2xx37)/(10xx10^(-2))`
`= 74xx10^(-6)T = 74 mu T`