Question

Point A in (Figure 1) is 4.5 mm from the wire. Assume that the wire is very long and that all other wires are too far away to contribute to the magnetic field. What is the magnetic field strength at point A?

Answer 1

Given

resistors 30 ohm and 20 ohm are in series net resistance is R20,30 = 30+20 = 50 ohm

and resistance 100 ohm and 50 ohm are in parallel to each other

now calculating the current through each resistor is I1 = 60/100 = 0.6 A, I2 = 60/50 = 1.2 A

now the point is A is at 4.5 mm = 0.0045 m from a wire of current carryin 1.2A ,

the magnetic field due toa current carrying conductor at a distance r is

   B = mue not*I/(2pi*r)
   B = 1.256*10^-6*1.2/(2pi*0.0045)T

   B = 53.3*10^-6 T

magnetic filed at point A is B = 53.3*10^-6 T