College Physics
College Physics
2nd Edition
ISBN: 9780134601823
Author: ETKINA, Eugenia, Planinšič, G. (gorazd), Van Heuvelen, Alan
Publisher: Pearson,
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Chapter 20, Problem 57RPP

BIO Power lines—do their magnetic fields pose a risk? Power lines produce both electric and magnetic fields. The interior of the human body is an electrical conductor, and as a result, electric fields are greatly reduced in magnitude within the body The electric fields inside the body from power lines are much smaller than electric fields normally existing in the body.

However, magnetic fields are not reduced in the body Earth's magnetic field, approximately 5   ×   10 5

T, is very small and not regarded as a health threat Thus, it is interesting to compare Earth's magnetic field to fields produced by high power lines The magnetic field B produced at a distance r from a straight wire with an electric current l is

B   = ( 2   ×   10 7  T  m/A ) I / r

The magnetic field from a high-voltage power line located 40 m above the ground carrying a 100-A current is much smaller than Earth's B field.

Wires that provide electric power for household appliances also produce electric and magnetic fields The current in the wire for a 500-W space heater is about 5 A. With the wire located several meters from your body the magnetic field of such an appliance is somewhat smaller than Earth’s magnetic field. By comparison laboratory mice lived for several generations in 0.0010-T magnetic fields (20 times Earth’s magnetic field) without any adverse effects.

During the last three decades, electric power use has increased the magnitudes of the B field created by power lines to which Americans are exposed by roughly a factor of 20. Yet during that same time interval, leukemia rates have slowly declined It seems unlikely that magnetic fields produced by home appliances or high-voltage power lines are a hazard for causing leukemia.

Why would scientists be more concerned about the relationship between magnetic fields and human health than about the relationship between electric fields and human health?

a. The human body is a conductor.

b. Many molecules are dipoles.

c. There are moving electrically charged particles inside the body.

d. Magnetic fields, if dangerous, are more likely to penetrate into the body.

e. Electric fields are reflected from clothing but magnetic fields are not.

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Chapter 20 Solutions

College Physics

Ch. 20 - Choose all that apply. Objects that produce...Ch. 20 - 5. What is one difference between magnetic and...Ch. 20 - 6. Two parallel straight current-carrying wires...Ch. 20 - 7. Choose all of the units that are fundamental,...Ch. 20 - 8. Particles of various masses, charges, and...Ch. 20 - When a diamagnetic material Is placed in an...Ch. 20 - If you triple the speed of a particle entering a...Ch. 20 - In 1911 physicists measured a magnetic field...Ch. 20 - Describe two experiments that will allow you to...Ch. 20 - How can you determine if there is a magnetic field...Ch. 20 - You have a magnet on which the poles are not...Ch. 20 - 15. List as many ways as you can to detect a...Ch. 20 - Prob. 16CQCh. 20 - Prob. 17CQCh. 20 - An electron flies through the magnetic field shown...Ch. 20 - Prob. 19CQCh. 20 - 20. A beam of electrons is not deflected as it...Ch. 20 - 21 A beam of electrons moving toward the east is...Ch. 20 - 22. Why are residents of northern Canada less...Ch. 20 - Prob. 23CQCh. 20 - An electron enters a solenoid at a small angle...Ch. 20 - Two parallel wires carry electric current in the...Ch. 20 - Prob. 26CQCh. 20 - Describe a situation in which an electron will be...Ch. 20 - When a switch is closed a compass needle deflects...Ch. 20 - 2. You have a lightbulb connected to a battery....Ch. 20 - 3 The current through a circuit is shown in Figure...Ch. 20 - 4. Draw field lines for the magnetic field...Ch. 20 - 5. * You need to determine the direction of the ...Ch. 20 - 6.* Two compass needles are fixed at the ends of a...Ch. 20 - 7. * In Houston, Earth’s field has a magnitude of...Ch. 20 - * A 15-g 10-cm-long wire is suspended horizontally...Ch. 20 - Prob. 9PCh. 20 - * A metal rod is connected to a battery through...Ch. 20 - * After you turned on the current in the circuit...Ch. 20 - 13. ** A square coil with 30 turns has sides that...Ch. 20 - * (a) Determine the magnetic force (magnitude and...Ch. 20 - 16. * A 500-turn square coil of wire is hinged to...Ch. 20 - * Electric motor 1 An electric motor has a square...Ch. 20 - 18. ** You make a seesaw by placing a 50-g magnet...Ch. 20 - * Electric motor 2 An electric motor has a...Ch. 20 - 20. Each of the lettered dots a-d shown In Figure...Ch. 20 - Duck gets a lift A duck accumulates a positive...Ch. 20 - 22. An electron of mass kg moves horizontally...Ch. 20 - A 1000-kg car moves west along the equator. At...Ch. 20 - * BIO Magnetic force exerted by Earth on ions in...Ch. 20 - 105m/s. Design a magnetic shield that will deflect...Ch. 20 - s magnetic field.Ch. 20 - 27. * An electron and a proton, moving side by...Ch. 20 - An east-west electric power line carries a 500-A...Ch. 20 - * Pigeons A solenoid of radius 1.0 m with 750...Ch. 20 - * A horizontal current-carrying wire that is...Ch. 20 - Prob. 31PCh. 20 - field inside a long solenoid is given by the...Ch. 20 - * Electron current and magnetic field in H atom In...Ch. 20 - * Two long, parallel wires are separated by 2.0 m....Ch. 20 - * Minesweepers During World War II, explosive...Ch. 20 - 40. An electron moves at the speed of toward the...Ch. 20 - * Mass spectrometer A mass spectrometer has a...Ch. 20 - 42. * Mass spectrometer 2 One type of mass...Ch. 20 - 43. * An ion with charge C moves at speed m/s...Ch. 20 - * A box has either an electric field or a magnetic...Ch. 20 - 45. ** A piece of wire, shown in Figure P20.45 ,...Ch. 20 - 46. ** EST Particles in cosmic rays are mostly...Ch. 20 - BIO Magnetic resonance imaging In magnetic...Ch. 20 - BIO Magnetic resonance imaging In magnetic...Ch. 20 - BIO Power lines—do their magnetic fields pose a...Ch. 20 - BIO Magnetic resonance imaging In magnetic...Ch. 20 - BIO Magnetic resonance imaging In magnetic...Ch. 20 - BIO Magnetic resonance imaging In magnetic...Ch. 20 - BIO Power linesdo their magnetic fields pose a...Ch. 20 - BIO Power linesdo their magnetic fields pose a...Ch. 20 - BIO Power linesdo their magnetic fields pose a...Ch. 20 - BIO Power linesdo their magnetic fields pose a...Ch. 20 - BIO Power linesdo their magnetic fields pose a...

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