Question

A magnet is suspended in such a way that it oscillates in the horizontal plane. It makes 20 oscillations per minute at a place where dip angle is 30⁰ and 15 oscillations per minute at a place where dip angle is 60⁰. The ratio of the total earth's magnetic field at the two places is –

• A. 3$\sqrt { 3 }$ : 8
• B. 16 : 9$\sqrt { 3 }$
• C. 4 : 9
• D. 2$\sqrt { 3 }$ : 9

Answer 1

Answer: (B)

16 : 9$\sqrt { 3 }$

Answer 2

T µ $\frac { 1 } { \sqrt { \mathrm {~B} } }$

$\frac { 3 } { 4 }$= $\sqrt { \frac { \mathrm { B } _ { \mathrm { H } _ { 2 } } } { \mathrm {~B} _ { \mathrm { H } _ { 1 } } } }$= $\sqrt { \frac { \mathrm { Be } _ { 2 } \cos 60 ^ { \circ } } { \mathrm { Be } _ { 1 } \cos 30 ^ { \circ } } }$

Ž $\frac { \mathrm { Be } _ { 1 } } { \mathrm { Be } _ { 2 } }$ = $\frac { 16 } { 9 \sqrt { 3 } }$