A square loop ABCD of side 8 cm lies flat on a horizontal table
MATHEMATICS · Multi-part · ISC · Physics · Magnetic Effects of Current and Magnetism · Ampere's circuital law
Problem
A square loop ABCD of side 8 cm lies flat on a horizontal table. A long straight wire passes vertically through the centre of the square carrying a current of 10 A downward (into the table). Mid-points of the four sides are labelled P (on AB), Q (on BC), R (on CD) and S (on DA).
(a) For the given direction of current in the wire, indicate the direction of the magnetic field at each of the points P, Q, R and S.
(b) Arrange the points P, Q, R and S in order of decreasing magnetic field strength, giving a clear justification for your order.
(c) If the direction of current in the wire is suddenly reversed while its magnitude remains 10 A, state the changes you would observe in the directions of the magnetic fields at P, Q, R and S and explain your reasoning.