An aerospace sensor uses a flat, circular search coil consisting of N=250N = 250N=250 turns of wire, each of cross-sectional area A=2.0×10−4 m2A = 2.0 \times 10^{-4}\text{ m}^2A=2.0×10−4 m2. The coil is placed in a vacuum chamber where a magnetic field is directed perpendicular to the plane of the coil.
The magnetic flux density B B\,B of this field varies with time t t\,t as shown in the graph below.
Which of the following descriptions correctly identifies the induced electromotive force (emf) ε \varepsilon\,ε in the coil during the two intervals of this 25.0 ms period?
The induced emf is constant at −1.2 V-1.2\text{ V}−1.2 V from t=0t = 0t=0 to 5.0 ms5.0\text{ ms}5.0 ms, and constant at +0.3 V+0.3\text{ V}+0.3 V from t=5.0 mst = 5.0\text{ ms}t=5.0 ms to 25.0 ms25.0\text{ ms}25.0 ms.
The induced emf is constant at +1.2 V+1.2\text{ V}+1.2 V from t=0t = 0t=0 to 5.0 ms5.0\text{ ms}5.0 ms, and constant at −0.3 V-0.3\text{ V}−0.3 V from t=5.0 mst = 5.0\text{ ms}t=5.0 ms to 25.0 ms25.0\text{ ms}25.0 ms.
The induced emf is constant at −0.3 V-0.3\text{ V}−0.3 V from t=0t = 0t=0 to 5.0 ms5.0\text{ ms}5.0 ms, and constant at +1.2 V+1.2\text{ V}+1.2 V from t=5.0 mst = 5.0\text{ ms}t=5.0 ms to 25.0 ms25.0\text{ ms}25.0 ms.
The induced emf is constant at +0.3 V+0.3\text{ V}+0.3 V from t=0t = 0t=0 to 5.0 ms5.0\text{ ms}5.0 ms, and constant at −1.2 V-1.2\text{ V}−1.2 V from t=5.0 mst = 5.0\text{ ms}t=5.0 ms to 25.0 ms25.0\text{ ms}25.0 ms.