Question
You MUST answer all parts of the question to receive points. That means answering parts A (i, ii) and parts B (i, ii)
The magnetic field shown has a uniform magnitude of 25.0 mT directed into the paper. The initial diameter of the kink in the wire is a 2.00 cm. The wire is quickly pulled taut and the kink shrinks to a diameter of zero in 50.0 ms. Determine the average voltage induced between the endpoints A and B. Include the polarity (i.e., which side is positive and which is negative). If the coil has a resistance of 10.0 Ohm, what is the magnitude and direction of the current in the coil during this time. Suppose the kink is undisturbed, but the magnetic field increases to 100 mT in 4.00 x 10-3 s. Determine the average voltage across terminals A and B, including polarity (i.e., which side is positive and which is negative), during this period. What is the magnitude and direction of the current in the coil during this time?
Explanation / Answer
Given magnitude of magnetic field B = 25 mT diameter of kink is 2 cm The wire is quickly pulled taut, and the kink shrinks to a diameter of zero in 50 ms emf induced between points A and B is ? = -d ? / dt = - B ( A2 - A1 ) / ( t 2 - t 1 ) = B A / t = 0.025 * ( ?*(1*10-2 ) 2 / 0.05 s = 0.5208*10-4 V = 0.0499 mV Suppose the kink is undisturbed, but the magnetic field increases to 100 mT in 4.0 x10-3 s ? = A dB / dt = A ( B 2 -B 1 ) ( t2 - t 1 ) = ( ?*(1*10-2 ) 2 ( 100-25 ) mT / 4 ms = 5.887 mV