COMEDK20269 May 2026Evening ShiftPhysicsElectromagnetic InductionActual
A metallic circular loop is placed with its plane perpendicular to a uniform magnetic field of 0.3 T. If the radius of the loop decreases at a constant rate of 2 mm s⁻¹ , what will be the induced emf in the loop, when the radius of the loop becomes 5 cm.
Options
- A1.89 10⁻⁴ V
- B0.75 10⁻⁶ V
- C1.84 10⁻⁶ V
- D1.5 10⁻⁶ V
Correct answer
A. 1.89 10⁻⁴ V
Step-by-step solution
Magnetic flux through the loop is given by = BA = B r^2 According to Faraday's law of induction, the magnitude of the induced emf is: |e| = | d dt | = B 2 r | dr dt | Given: B = 0.3 T r = 5 cm = 5 10⁻² m | dr dt | = 2 mm s⁻¹ = 2 10⁻³ m s⁻¹ Substituting the values: |e| = 0.3 2 (5 10⁻²) (2 10⁻³) |e| = 0.3 20 10⁻⁵ = 6 10⁻⁵ V |e| = 6 22 7 10⁻⁵ 18.857 10⁻⁵ V |e| 1.89 10⁻⁴ V Answer: 1.89 10⁻⁴ V