Chapter 23, Problem 98PP

A truck drives onto a loop detector and increases the downward component of the magnetic field within the loop from 1.2 × 10⁻⁵ T to the larger value B in 0.38 s. The detector is circular, has a radius of 0.67 m, and consists of three loops of wire. What is B, given that the induced emf is 8.1 × 10⁻⁴V?

1. A.    3.6 × 10⁻⁵T
2. B.     7.3 × 10⁻⁵T
3. C.     8.5 × 10⁻⁵T
4. D.    24 × 10⁻⁵T