Part A = There is no magnetic flux through the wire loop.

Part B = There is no induced current.

Part C = The induced current is counterclockwise.

Part D = B, B

When the switch is open, which of the following statements about the magnetic flux through the wire loop is true? Assume that the direction of the vector area of the wire loop is to the right.

What is the direction of the induced current in the wire loop (as seen from the left) when the switch is open?

Now the switch on the electromagnet is closed. What is the direction of the induced current in the wire loop immediately after the switch is closed (as seen from the left)?

Finally, the switch on the electromagnet is reopened. The magnitude of the external magnetic flux through the wire loop ______ (A. increases, B. decreases, C. remains constant), and there is _______ (A. zero, B. a clockwise, C. a counterclockwise) current induced in the loop (as seen from the left).

Part A = 0.33 m^{2}

Part B = 42 V

Part C = 83 V

A uniform magnetic field is at right angles to the plane of a wire loop. The field decreases by 0.25 T in 1.0*10^−3 s and the magnitude of the average emf induced in the loop is 83 V.

What is the area of the loop?

What would be the value of the average induced emf if the field change was the same but took twice as long to decrease?

What would be the value of the average induced emf if the field decrease was twice as much and it also took twice as long to change?

Part A = 1.7 V

Part B = 0.44 V

A square loop of wire with sides of length 40 cm is in a uniform magnetic field perpendicular to its area.

If the field’s strength is initially 120 mT and it decays to zero in 0.011 s, what is the magnitude of the average emf induced in the loop?

What would be the average emf if the sides of the loop were only 20 cm?

Part A = south

A bar magnet is thrust toward the center of a circular metallic loop. The magnet approaches perpendicularly with its length perpendicular to the coil’s plane. As the bar recedes from your view and approaches the coil, a clockwise current is induced in the loop. What polarity is that end of the bar magnet nearest the coil?

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Part A = clockwise

Part B = no current

Part C = counterclockwise

A loop of wire is initially held above a short solenoid. A constant counterclockwise (as viewed from above) current passes through the turns of the solenoid. The loop of wire is steadily lowered, eventually “encircling” the solenoid.

What is the direction of the induced current in the loop when the loop is above the solenoid, moving downward?

What is the direction of the induced current at the instant that the loop is at the midpoint of the solenoid and still moving downward?

What is the direction of the induced current when the loop is below the solenoid and moving downward?

Part A = twice as great

Part B = unchanged

When a magnet is plunged into a coil at speed v, as shown in the figure, a voltage is induced in the

coil and a current flows in the circuit.

If the speed of the magnet is doubled, the induced voltage is?

The same magnet is plunged into a coil that has twice the number of turns as before. The magent

is shown before it enters the coil in the figure. If the speed of the magnet is again , the induced

current in the coil is?