Suppose you are holding a circular ring of wire and suddenly thrust a magnet, south pole first, away from you toward the center of the circle. Is a current induced in the wire? Is a current induced when the magnet is held steady within the ring? Is a current induced when you withdraw the magnet? In each case, if your answer is yes, specify the direction.

Suppose you are holding a circular ring of wire in front of you and suddenly thrust a magnet, south pole first, away from you toward the center of the circle. Is a current induced when you withdraw the magnet? For each yes answer, specify the direction. Explain your answer.

Explain the difference between a magnetic field and a magnetic flux.

An electron is moving in a circular orbit in the earth's magnetic field directly above the north magnetic pole. Viewed from above, is the rotation clockwise or counterclockwise?

Can you set a resting electron into motion with a magnetic field? With an electric field? Explain.

While demonstrating Faraday's law to her class, a physics professor inadvertently moves the gold ring on her finger from a location where a $0.68 \mathrm{~T}$ magnetic field points along her finger to a zero-field location in $45 \mathrm{~ms}$. The $1.5 \mathrm{~cm}$ diameter ring has a resistance and mass of $55 \mu \Omega$ and $15 \mathrm{~g}$, respectively. Find the temperature rise of the ring, assuming all of the thermal energy produced goes into increasing the ring's temperature. The specific heat of gold is $129 \mathrm{~J} / \mathrm{kg} \cdot \mathrm{C}^{\circ}$.

The back emf in a motor is 95 V when the motor is operating at 1000 rpm. How would you change the motor's magnetic field if you wanted to reduce the back emf to 65 V when the motor was running at 2500 rpm?

Compare the oscillations of an LC circuit to the vibration of a mass m on a spring. What do L and C correspond to in the mechanical system?

A charged particle is moving in a circle under the influence of a uniform magnetic field. If an electric field that points in the same direction as the magnetic field is turned on, describe the path the charged particle will take.

Draw the magnetic field lines around a straight section of wire carrying a current horizontally to the left.

Two identical bar magnets are dropped vertically from the same height. One magnet passes through an open metal ring, and the other magnet passes through a closed metal ring. Which magnet will reach the ground first? (a) The magnet passing through the closed ring (b) The magnet passing through the open ring (c) The magnets arrive at the ground at the same time. (d) There is too little information to answer this question.

Two coils are placed next to each other on the table. The coil on the right is connected in series to a battery and a switch. With the switch closed, there is a clockwise current in the right coil as seen from above. When the switch is opened, the current in the right coil decreases abruptly to zero. What is the induced current in the coil on the left as seen from above while the current in the right coil decreases? (a) Clockwise (b) Counterclockwise (c) Zero because the current is only present when the coils move relative to each other (d) Zero because there is no magnetic field through the coil on the left

A dc generator is rated at 10 kW, 200 V, and 50 A when it rotates at $1000$ rpm. The resistance of the armature windings is $0.40 ~\Omega$. (a) Calculate the "no-load" voltage at $1000$ rpm (when there is no circuit hooked up to the generator). (b) Calculate the full-load voltage (i.e. at $50 ~\mathrm{A}$) when the generator is run at $800$ rpm. Assume that the magnitude of the magnetic field remains constant.

While demonstrating Faraday's law to her class, a physics professor inadvertently moves the gold ring on her finger from a location where a $0.68 \mathrm{~T}$ magnetic field points along her finger to a zero-field location in $45 \mathrm{~ms}$. The $1.5 \mathrm{~cm}$ diameter ring has a resistance and mass of $55 \mu \Omega$ and $15 \mathrm{~g}$, respectively. Estimate the thermal energy produced in the ring due to the flow of induced current.