COMEDK2024PhysicsElectromagnetic InductionActual
A wire ' l ' m long bent into a circular loop is placed perpendicular to the magnetic field of flux density B Wbm ⁻² . Within 0.1sec, the loop is changed into a square of side ' a ' m and flux density is doubled. The value of e.m.f. induced is
Options
- A5 B (8 a^2-l^2 ) 2
- B-5 B (8 a^2-l^2 ) 2
- C-5 B (8 a ^2- l ^2 ) 2
- D-5 B (8 a^2-l^2 ) 2
Correct answer
B. -5 B (8 a^2-l^2 ) 2
Step-by-step solution
Initial flux: ₁ = B r^2 = B ( l 2 )^2 = Bl^2 4 Final flux: ₂ = 2B a^2 = 2Ba^2 Induced e.m.f.: e = - t = - 2Ba^2 - Bl^2 4 0.1 e = -10B ( 8 a^2 - l^2 4 ) = -5B(8 a^2 - l^2) 2