Question

Two identical bar magnets are placed on above the other such that they are mutually perpendicular and bisect each other. The time period of this combination in a horizontal magnetic field is T. The time period of each magnet in the same field is

• A. $\sqrt { 2 } T$
• B. $2 ^ { \frac { 1 } { 4 } } T$
• C. $2 ^ { - \frac { 1 } { 4 } } T$
• D. $2 ^ { - \frac { 1 } { 2 } } T$

Answer 1

Answer: (C)

$2 ^ { - \frac { 1 } { 4 } } T$

Answer 2

Time period of combination

$T = 2 \pi \sqrt { \frac { 2 I } { \sqrt { 2 } M \cdot H } }$ …..(i)

and time period of each magnet

$T ^ { \prime } = 2 \pi \sqrt { \frac { I } { M H } }$ ……(ii)

From (i) and (ii) we get

$T ^ { \prime } = \frac { T } { 2 ^ { 1 / 4 } } = 2 ^ { - 1 / 4 } T$