question_answer

A thin strip 10 cm long is on a U shaped wire of negligible resistance and it is connected to a spring of spring constant 0.5 \[N{{m}^{-1}}\] (see figure). The assembly is kept in a uniform magnetic field of 0.1 T. If the strip is pulled from its equilibrium position and released, the number of oscillation it performs before its amplitude decreases by a factor of e is N. If the mass of the strip is 50 grams, its resistance \[10\Omega \]and air drag negligible, N will be close to : [JEE Main 8-4-2019 Morning]

A) 50000

B) 5000

C) 10000

D) 1000

Correct Answer: B

Solution :

[b]

for

No of oscillation.