AP EAMCET · PHYSICS · Magnetic Properties of Matter

A compass needle oscillates $20$ times per minute at a place where the dip is $45 °$ and the magnetic field is $B_{1}$ . The same needle oscillates 30 times per minute at a place where the dip is $30 °$ and magnetic field is $B_{2}$ . Then $B_{1} : B_{2}$ is

A $9 \sqrt{3} : 4 \sqrt{2}$
B $4 \sqrt{2} : 9 \sqrt{3}$
C $3 \sqrt{3} : 2 \sqrt{2}$
D $2 \sqrt{2} : 3 \sqrt{3}$

Verified Solution

Answer & Solution

Correct Answer

(D) $2 \sqrt{2} : 3 \sqrt{3}$

Step-by-step Solution

Detailed explanation

The frequency of oscillations of a magnetic needle in earth’s magnetic field is given as f=12πμBHI, where, horizontal component of earth’s magnetic field BH=Bcosθ, μ is the magnetic moment of the magnetic needle and I is moment of inertia of the…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Explore more questions on app

From AP EAMCET

Explore more questions on app

A compass needle oscillates 20 times per minute at a place where the dip is 45° and the magnetic field is B1. The same needle oscillates 30 times per minute at a place where the dip is 30° and magnetic field is B2. Then B1:B2 is

Step-by-step Solution

A compass needle oscillates $20$ times per minute at a place where the dip is $45 °$ and the magnetic field is $B_{1}$ . The same needle oscillates 30 times per minute at a place where the dip is $30 °$ and magnetic field is $B_{2}$ . Then $B_{1} : B_{2}$ is