Chapter 25 Electromagnetic Induction and Electromagnetic Waves
Chapter 25 Electromagnetic Induction and Electromagnetic Waves
Chapter 25 Electromagnetic Induction and Electromagnetic Waves
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<strong>Chapter</strong> <strong>25</strong> <strong>Electromagnetic</strong> <strong>Induction</strong> <strong>and</strong> <strong>Electromagnetic</strong> <strong>Waves</strong><br />
Wednesday, March 24, 2010<br />
3:16 PM
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CP 3 A 10-cm-long wire is pulled along a U-shaped<br />
conducting rail in a perpendicular magnetic field. The total<br />
resistance of the wire <strong>and</strong> rail is 0.20 Ω. Pulling the wire with<br />
a force of 1.0 N causes 4.0 W of power to be dissipated in the<br />
circuit. (a) Determine the speed of the wire. (b) Determine<br />
the strength of the magnetic field.<br />
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CP 14 Patients undergoing an MRI scan occasionally report<br />
seeing flashes of light. Some practitioners assume that this<br />
results from electrical stimulation of the eyes by the emf<br />
induced by the rapidly changing fields of an MRI solenoid.<br />
We can do a quick calculation to see if this is a reasonable<br />
assumption. The human eyeball has a diameter of about <strong>25</strong><br />
mm. Rapid changes in current in an MRI solenoid can<br />
produce rapid changes in the magnetic field, with B/ t as<br />
large as 50 T/s. How much emf would this induce in a loop<br />
circling the eyeball? How does this compare with the 15 mV<br />
necessary to trigger an action potential?<br />
CP 15 A 1000-turn coil of wire 2.0 cm in diameter is in a<br />
magnetic field that drops from 0.10 T to 0 T in 10 ms. The<br />
axis of the coil is parallel to the field. Determine the emf in<br />
the coil.
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the coil.<br />
CP 18 A 5.0-cm-diameter loop of wire has resistance 1.2 Ω.<br />
A nearby solenoid generates a uniform magnetic field<br />
perpendicular to the loop that varies with time as shown<br />
in the figure. Graph the magnitude of the current in the<br />
loop over the same time interval.<br />
CP 21 A microwave oven operates at 2.4 GHz with an<br />
intensity inside the oven of <strong>25</strong>00 W/m 2 . Determine the<br />
amplitudes of the oscillating electric <strong>and</strong> magnetic fields.
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amplitudes of the oscillating electric <strong>and</strong> magnetic fields.<br />
CP 29 At what distance from a 10 W point source of<br />
electromagnetic waves is the electric field amplitude<br />
(a) 100 V/m, <strong>and</strong> (b) 0.010 V/m.
CP 31 Only <strong>25</strong>% of the intensity of a polarized light wave<br />
passes through a polarizing filter. What is the angle between<br />
the electric field <strong>and</strong> the axis of the filter?<br />
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CP 43 The spectrum of a glowing filament has its peak at a<br />
wavelength of 1200 nm. Determine the temperature of the<br />
filament in degrees Celsius.<br />
CP 57 A 100-turn, 8.0-cm-diameter coil is made of 0.50-mm<br />
diameter copper wire. A magnetic field is perpendicular to the<br />
coil. At what rate must B increase to induce a 2.0 A current in<br />
the coil?
CP 58 The loop in the figure is being pushed into the 0.20 T<br />
magnetic field at a speed of 50 m/s. The resistance of the loop<br />
is 0.10 Ω. Determine the direction <strong>and</strong> magnitude of the<br />
current in the loop.<br />
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