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A boat travels straight toward the east in a place where Earth’s magnetic field is horizontal, points due north, and has magnitude 5.0 × 10⁻⁵ N A⁻¹ m⁻¹. A 2 m long vertical antenna is mounted on the boat. If the boat’s speed is 1.50 m s⁻¹, what emf is induced across the antenna wire?

1. 0.75 mV
2. 0.50 mV
3. 0.15 mV
4. 1 mV

Correct answer: 0.15 mV

Solution

v (east) x B (north) is vertical, along the vertical antenna, so emf = B*L*v = 5*10^-5 * 2 * 1.5 = 1.5*10^-4 V = 0.15 mV.

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