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Question:

For MRI, a patient is slowly pushed in a time of 10 s within the coils of the magnet where magnetic field is B = 2.0 T. If the patient's trunk is 0.8 m in circumference, the induced emf around the patient's trunk is?

10.18×10𕒶V

9.66×102V

10.18×10𕒷V

1.51×10𕒶V

Solution:

Change in magnetic field in 10 s = 2.0 T
As ε = −dΦ/dt = −A dB/dt (≈ Φ = BA)
Circumference of patient's trunk, 2πr = 0.8 m (given)
∴r = 0.8/2π m = 0.4π m
Area of cross section, A = πr² = π(0.4π)² = 0.16π m²
∴|ε| = 0.16π × 2/10 V ≈ 10.18 × 10⁻²V