Practice portal › Moving Charges and Magnetism › Torque on a Current Loop and Magnetic Dipole Moment

A wire carrying current I is bent in the shape ABCDEFA as shown, where rectangle ABCDA and ADEFA are perpendicular to each other. If the sides of the rectangles are of lengths a and b, then the magnitude and direction of magnetic moment of the loop ABCDEFA is

Asked in JEE Main 2nd Sept 2nd Shift 2020 · Magnetic moment of loops and charges

• (1) abI, along ((ȷ̂)/(√5) + (2k̂)/(√5))
• (2) √2 abI, along ((ȷ̂)/(√2) + (k̂)/(√2))
• (3) √2 abI, along ((ȷ̂)/(√5) + (2k̂)/(√5))
• (4) abI, along ((ȷ̂)/(√2) + (k̂)/(√2))

Step-by-step solution

Why the other options are wrong

• (1) Gave one rectangle twice the area of the other and took only one moment's magnitude.
• (3) Right magnitude but wrong direction: the two rectangles have equal areas, so the components are equal.
• (4) Took the magnitude of a single rectangle instead of adding two perpendicular moments of abI each.

Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.