(a) Using the expression provided for the flux, show that the magnitude of the induced emf as a function of time is given by |E| = Bπr² (2π f) sin(2π ft). (b) Using your result from part (a), Ohm's law, and the numerical values given in the problem, find the radius of the loop. (c) If the loop is rotated more slowly, then if we wanted to get the same induced current we would need a larger loop. Explain why this is true, and check that your solution is consistent with this prediction.
(a) Using the expression provided for the flux, show that the magnitude of the induced emf as a function of time is given by |E| = Bπr² (2π f) sin(2π ft). (b) Using your result from part (a), Ohm's law, and the numerical values given in the problem, find the radius of the loop. (c) If the loop is rotated more slowly, then if we wanted to get the same induced current we would need a larger loop. Explain why this is true, and check that your solution is consistent with this prediction.
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Transcribed Image Text:Problem 4
Your textbook calls the electric generator "probably the most important technological application of
induction." Let's consider an example of such a generator, consisting of a single round loop of wire of
R = 100. The loop is rotated at a frequency f of 60 turns per second (and thus at 60 × 2 radians
per second). As shown in the figure below, the rotation axis of the loop is through its diameter and
perpendicular to the page, and the loop rotates clockwise. We place the loop in a uniform magnetic
field of strength B = 0.50 T that points to the right. Note that the loop is arranged so that its
rotation axis is perpendicular to the field. The angle measures the angle between the field and the
normal onto the plane of the loop. An oscillating current with an amplitude of Io = 1.5 A is induced.
B
Pivot
Circular loop
Assuming we let t = 0 correspond to 0 = 0° (i.e., the loop is vertical), the flux through the loop as
a function of time is given by
PB (t) = Bлr² сos (2π ft),
where r is the (unknown) radius of the loop.
Transcribed Image Text:(a) Using the expression provided for the flux, show that the magnitude of the induced emf as a
function of time is given by
|E| = Bπr² (2π f) sin(2π ft).
(b) Using your result from part (a), Ohm's law, and the numerical values given in the problem, find
the radius of the loop.
(c) If the loop is rotated more slowly, then if we wanted to get the same induced current we would
need a larger loop. Explain why this is true, and check that your solution is consistent with this
prediction.
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