23.4 Eddy Currents and Magnetic Damping Eddy Currents and Magnetic Damping As discussed in Motional Emf, motional emf is induced when a conductor moves in a magnetic field or when a magnetic field moves relative to a conductor. If motional emf can cause a current loop in the conductor, we refer to that current as an eddy current. Eddy currents can produce significant drag, called magnetic damping, on the motion involved. Consider the apparatus shown in Figure 23.13, which swings a pendulum bob between the poles of a strong magnet. (This is another favorite physics lab activity.) If the bob is metal, there is significant drag on the bob as it enters and leaves the field, quickly damping the motion. If, however, the bob is a slotted metal plate, as shown in Figure 23.13(b), there is a much smaller effect due to the magnet. There is no discernible effect on a bob made of an insulator. Why is there drag in both directions, and are there any uses for magnetic drag? Pivot Pivot Pivot N. (a) (b) (c) Figure 23.13 A common physics demonstration device for exploring eddy currents and magnetic damping. (a) The motion of a metal pendulum bob swinging between the poles of a magnet is quickly damped by the action of eddy currents. (b) There is little effect on the motion of a slotted metal bob, implying that eddy currents are made less effective. (c) There is also no magnetic damping on a nonconducting bob, since the eddy currents are extremely small.
23.4 Eddy Currents and Magnetic Damping Eddy Currents and Magnetic Damping As discussed in Motional Emf, motional emf is induced when a conductor moves in a magnetic field or when a magnetic field moves relative to a conductor. If motional emf can cause a current loop in the conductor, we refer to that current as an eddy current. Eddy currents can produce significant drag, called magnetic damping, on the motion involved. Consider the apparatus shown in Figure 23.13, which swings a pendulum bob between the poles of a strong magnet. (This is another favorite physics lab activity.) If the bob is metal, there is significant drag on the bob as it enters and leaves the field, quickly damping the motion. If, however, the bob is a slotted metal plate, as shown in Figure 23.13(b), there is a much smaller effect due to the magnet. There is no discernible effect on a bob made of an insulator. Why is there drag in both directions, and are there any uses for magnetic drag? Pivot Pivot Pivot N. (a) (b) (c) Figure 23.13 A common physics demonstration device for exploring eddy currents and magnetic damping. (a) The motion of a metal pendulum bob swinging between the poles of a magnet is quickly damped by the action of eddy currents. (b) There is little effect on the motion of a slotted metal bob, implying that eddy currents are made less effective. (c) There is also no magnetic damping on a nonconducting bob, since the eddy currents are extremely small.
Chapter8: Electromagnetism And Em Waves
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Eddy Currents and Magnetic Damping
• Explain the magnitude and direction of an induced eddy current, and the effect this will have on the object it is
induced in.
• Describe several applications of magnetic damping.
Transcribed Image Text:23.4 Eddy Currents and Magnetic Damping
Eddy Currents and Magnetic Damping
As discussed in Motional Emf, motional emf is induced when a conductor moves in a magnetic field or when a magnetic field
moves relative to a conductor. If motional emf can cause a current loop in the conductor, we refer to that current as an eddy
current. Eddy currents can produce significant drag, called magnetic damping, on the motion involved. Consider the apparatus
shown in Figure 23.13, which swings a pendulum bob between the poles of a strong magnet. (This is another favorite physics
lab activity.) If the bob is metal, there is significant drag on the bob as it enters and leaves the field, quickly damping the motion.
If, however, the bob is a slotted metal plate, as shown in Figure 23.13(b), there is a much smaller effect due to the magnet.
There is no discernible effect on a bob made of an insulator. Why is there drag in both directions, and are there any uses for
magnetic drag?
Pivot
Pivot
Pivot
N.
(a)
(b)
(c)
Figure 23.13 A common physics demonstration device for exploring eddy currents and magnetic damping. (a) The motion of a metal pendulum bob
swinging between the poles of a magnet is quickly damped by the action of eddy currents. (b) There is little effect on the motion of a slotted metal bob,
implying that eddy currents are made less effective. (c) There is also no magnetic damping on a nonconducting bob, since the eddy currents are
extremely small.
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