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 magne…

Question

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

Accepted Answer

Correct answer: D. (a) We have that T=2 I MB_H T ∝ 1 B_H T ∝ 1 Bcos ⇒B ∝ 1 T^2 cos So, B_1B_2= ( T_2T_1 )^2 cos ⁡ _2 cos ⁡ _1 = ( 3020 )^2 3 22 1 = 94 3 22 = 9 34 2

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

Solution

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