A magnetic needle has a frequency of 20 oscillations per minute in the earth’s horizontal field. when the field of a magnet supports the earths horizontal field, the frequency increases to 30 oscillations per minute. The ratio of the field of the magnet to that of the earth is

see full answer

Start JEE / NEET / Foundation preparation at rupees 99/day !!

21% of IItians & 23% of AIIMS delhi doctors are from Sri Chaitanya institute !!

An Intiative by Sri Chaitanya

7:4

4:5

4:7

5:4

answer is C.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

$\begin{array}{l} \frac{n_{1}}{n_{2}} = \sqrt{\frac{B_{H}}{B + B_{H}}}; \\ \frac{20}{30} = \sqrt{\frac{B_{H}}{B + B_{H}}} \Rightarrow \frac{B + B_{H}}{B_{H}} = 9 / 4; \frac{B}{B_{H}} = 5 / 4 \end{array}$

Watch 3-min video & get full concept clarity

hear from our champions

Result Producing online coaching for JEE/NEET of south India

Largest All India Test Series for JEE/NEET

Best Books for IIT JEE

Best Books for NEET

🔥 Start Your JEE/NEET Prep at Just ₹1999 / month - Limited Offer! Check Now!

Get Expert Academic Guidance – Connect with a Counselor Today!

Result Producing online coaching for JEE/NEET of south India

Largest All India Test Series for JEE/NEET

Best Books for IIT JEE

Best Books for NEET