Mastering Physics- Induced EMF and Current in a Shrinking Loop?

Shrinking Loop. A circular loop of flexible iron wire has an initial circumference of 168 cm, but its circumference is decreasing at a constant rate of 15.0 cm/s due to a tangential pull on the wire. The loop is in a constant uniform magnetic field of magnitude 1.00 T, which is oriented perpendicular to the plane of the loop. Assume that you are facing the loop and that the magnetic field points into the loop.

Answer

induced emf V = d(B*A)/dt = B*dA/dt B = 1.00 T A = pi*r^2 circumference c = 2pi*r r = c / 2pi so A = pi*(c / 2pi)^2 A = c^2 / 4pi so dA/dc = c / 2pi = r dA/dt = dA/dc * dc/dt dc/dt = -15 cm/s = -0.15 m/s At t = 8.00s, c = 168 – (8*15)m = 48 cm = 0.48m so dA/dc = r = 0.48m / 2pi = 0.0764 m so dA/dt = 0.0764m * 0.15 m/s = 0.01146 m^2 /s so E = 1.00T * 0.01146 m^2/s = 0.01146V = 11.5 mV <= ANS

Leave a Comment