AP® Physics C: E&M - Induced Currents and Magnetic Forces - MCQs
Quesstions
A metal wire of resistance 10 Τ is bent into a circular hoop of radius 0.10 meter and placed in a uniform magnetic field, as shown in Figure 1 above. The magnetic field strength B as a function of time is shown in Figure 2, where positive refers to a magnetic field directed out of the page. What are the magnitude and direction of the current induced in the ring at time t = 6 s?
Magnitude Direction
(A) 3.8 mA Clockwise
(B) 3.8 mA Counterclockwise
(C) 0.42 mA Clockwise
(D) 0.42 mA Counterclockwise
(E) 0 No direction
▶️Answer/Explanation
Ans: D
Questions
A loop of wire lies in the plane of the page in a region with a uniform magnetic field B directed into the page, as shown in the figure above. In which of the following cases, if any, will an emf be induced in the loop at the moment shown in the figure?
(A) The loop is moving toward the right.
(B) The loop is moving toward the top of the page.
(C) The loop is moving out of the plane of the paper so that the loop’s plane remains perpendicular to the magnetic field.
(D) The loop is moving into the plane of the paper so that the loop’s plane remains perpendicular to the magnetic field.
(E) An emf cannot be induced in the loop without changing its orientation relative to the magnetic field.
▶️Answer/Explanation
Ans: E
Questions
A permanent magnet of mass M is dropped down the interior of a hollow cylindrical tube made of copper, as shown at left in the figure above. Friction between the inside of the tube and the magnet is negligible. As the magnet moves downward, an upward magnetic force \(F_{B}\) induced, and the magnet’s velocity quickly reaches a constant terminal value \(V_{T}\) . A nonmagnetic object of mass M is attached to the permanent magnet and the drop is repeated, as shown at right in the figure above. When terminal velocity is reached, how do the new values of \(F_{B}\) and \(V_{T}\) compare with their values without the object?
▶️Answer/Explanation
Ans: D