Question

magnetic field shown in Figure 4 has a uniform magnitude of 25.0 mT paper. The initial diameter of the kink is 2.00 cm. (a) The wire is 3. The directed into the quickly pulled taut, and the kink shrinks to a diameter of zero in 50.0 ms. Determine the average voltage induced between endpoints A and B. Include the polarity. (b) Suppose the kink is undisturbed, but the magnetic field increases to 100 mT in 4.00 x10" s. Determine the average voltage across terminals A and B, including polarity, during this period. (15) 2.00 cm Figure 4

Answer 1

(a) Initially Area of kink = A = pi r^2 oR A = 3.14 times (10^-2)^2 = 3.14 times 10^-4 m^2 Final area of kink = 0 so average voltage = B times dA/dt = 25.0 times 10^-3 times (3.14 times 10^-4/50 times 10^-3) = 25.0 times 10^-3 times 0.0628 times 10^-1 volt = 1.57 times 10^-4 volt V_avg = 1.57 times 10^-4 volt and polarity with A in (-) negative and end B is positive (b) dB/dt = +(100 - 25) times 10^-3/4.00 times 10^3 = 18.75 times 10^-6 T/5 and so average voltage = V_avg = dB/dt times A OR V_avg = 18.75 times 10^-6 times 3.14 times 10^-4 = 5.8875 times 10^-8 volt V_avg = 5.8875 times 10^-8 volt and polarity with A is (+) positive and B is (-) negative Polarity is obtained from lenz law