Question

Find the magnetic field intensity at the radius of 6cm of a coaxial cable with inner and outer radii are 1.5cm and 4cm respectively. The current flowing is 2A.

(a) 2.73

(b) 3.5

(c) 0

(d) 1.25

The question was posed to me during an interview.

Question is taken from Magnetic Field Intensity topic in chapter Magnetostics of Electromagnetic Theory

Answer 1

The correct choice is (c) 0

For explanation: The inner radius is 1.5cm and the outer radius is 4cm. It is clear that the magnetic field intensity needs to be calculated outside of the conductor ie, r>4cm. This will lead to zero, since H outside the conductor will be zero.