Case : Read the passage and answer the question(s).
Magnetic Field of a hollow wire with a constant current is homogenous. Curves in the graph shown, give, as functions of distance r, the magnitude B of the magnetic field inside and outside four long wires a, b, c and d carrying currents that are uniformly distributed across the cross sections of the wires. Overlapping portions of the plots are indicated by double labels.
What is true about magnetic field if a direct current I flows along the length of an infinitely long straight thin walled pipe?
Answer & explanation
Correct answer: option 3
The amperian loop imagined inside the pipe will not enclose any current and hence using ampere circuital law, magnetic field is zero.