Question

If the key in the arrangement (Figure) is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are 

(a) concentric circles 

(b) elliptical in shape 

(c) straight lines parallel to each other

(d) concentric circles near the point O but of elliptical shapes as we go away from it

Answer 1

Correct option is (c) straight lines parallel to each other

We know that magnetic field produced  due to current flow. When current is not flow, then magnetic field line not produced. But magnetic field at ground exits, if we see a small point on the ground magnetic field line will be uniform, in case of uniform magnetic field, line will be straight lines parallel to each other.