JEE Main 2026 Physics question
A 30 cm long solenoid has 10 turns per cm and area of 5 cm². The current through the solenoid coil varies from 2 A to 4 A in 3.14 s. The e.m.f. induced in the coil is α×10⁻⁵ V. The value α is .
Answer: (B)
Solution
n=1000 turns/m. L=μ₀n²Al=4π×10⁻⁷×10⁶×5×10⁻⁴×0.3=1.885×10⁻⁴ H (π=3.14). EMF=L ΔI/Δt=1.885×10⁻⁴×2/3.14=1.2×10⁻⁴ V=12×10⁻⁵ V.