True or false: A charged particle must move in a

Magnetism By whom, and in what setting, was the relationship between electricity and magnetism discovered?

Magnetism The force between electrically charged particles depends on the magnitude of each charge, their separation distance, and what else?

Magnetism What is the source of magnetic force?

Magnetic Poles Is the rule for the interaction between magnetic poles similar to the rule for the interaction between electrically charged particles?

In what way are magnetic poles very different from electric charges?

Magnetic Fields How does magnetic field strength relate to the closeness of magnetic field lines about a bar magnet?

Magnetic Fields What produces a magnetic field?

Magnetic Fields What two kinds of rotational motion do electrons in an atom appear to have?

What is a magnetic domain?

Magnetic Domains At the micro level, what is the difference between an unmagnetized iron nail and a magnetized iron nail?

Magnetic Domains Why will dropping an iron magnet on a concrete sidewalk make it a weaker magnet?

Electric Currents and Magnetic Fields In Chapter 22, we learned that the direction of the electric field about a point charge is radial to the charge. What is the direction of the magnetic field surrounding a current-carrying wire?

Electric Currents and Magnetic Fields What happens to the direction of the magnetic field about an electric current when the direction of the current is reversed?

Electric Currents and Magnetic Fields Why is the magnetic field strength greater inside a current carrying loop of wire than about a straight section of wire?

Electromagnets Why does a piece of iron in a current-carrying loop increase the magnetic field strength?

Electromagnets Why are the magnetic fields of superconducting magnets often stronger than those of conventional magnets?

Magnetic Forces True or false: A charged particle must move in a stationary magnetic field in order that a force due to the field act on it.

Magnetic Forces In what direction relative to a magnetic field does a charged particle move in order to experience maximum deflecting force? Minimum deflecting force?

Magnetic Forces What effect does Earth’s magnetic field have on the intensity of cosmic rays striking Earth’s surface?

What relative direction between a magnetic field and a current-carrying wire results in the greatest force?

Magnetic Forces How does a galvanometer detect electric current?

Magnetic Forces What is a galvanometer called when it has been calibrated to read current? When it has been calibrated to read voltage?

How often is current reversed in the loops of an electric motor?

Magnetic Forces Is it correct to say that an electric motor extends the physics that underlies a galvanometer?

Earth’s Magnetic Field Why are there probably no permanently aligned magnetic domains in Earth’s core?

What are magnetic pole reversals?

What is the cause of the aurora borealis (northern lights)?

Biomagnetism Name at least six creatures that are known to harbor tiny magnets within their bodies.

Many dry cereals are fortified with iron, which is added to the cereal in the form of small iron particles. How might these particles be separated from the cereal?

In what sense are all magnets electromagnets?

All atoms have moving electric charges. Why, then, aren’t all materials magnetic?

To make a compass, point an ordinary iron nail along the direction of Earth’s magnetic field (which, in the Northern Hemisphere, is angled downward as well as northward) and repeatedly strike it for a few seconds with a hammer or a rock. Then suspend it at its center of gravity by a string. Why does the act of striking magnetize the nail?

If you place a chunk of iron near the north pole of a magnet, attraction will occur. Why will attraction also occur if you place the same iron near the south pole of the magnet?

Do the poles of a horseshoe magnet attract each other? If you bend the magnet so that the poles get closer together, what happens to the force between the poles?

Why isn’t it advisable to make a horseshoe magnet from a flexible material?

What kind of force field surrounds a stationary electric charge? What additional field surrounds it when it moves?

What is different about the magnetic poles of common refrigerator magnets and those of common bar magnets?

A friend tells you that a refrigerator door, beneath its layer of painted plastic, is made of aluminum. How could you check to see if this is true (without any scraping)?

Why will a magnet attract an ordinary nail or paper clip but not a wooden pencil?

Will either pole of a magnet attract a paper clip? Explain what is happening inside the attracted paper clip. (Hint: Consider Figure 22.13.)

\(47\). By what mechanism do the iron filings shown about the magnet in Figure \(24.2\) align with the magnetic field? Equation Transcription: Text Transcription: 47 24.2

One way to make a compass is to stick a magnetized needle into a piece of cork and float it in a glass bowl full of water. The needle will align itself with horizontal component of Earth’s magnetic field. Since the north pole of this compass is attracted northward, will the needle float toward the north side of the bowl? Defend your answer.

The north pole of a compass is attracted to the north magnetic pole of Earth, yet like poles repel. What does this indicate about the polarity of Magnet Earth at its poles?

We know that a compass points northward because Earth is a giant magnet. Will the northward-pointing needle point northward when the compass is brought to the Southern Hemisphere?

In what position can a current-carrying loop of wire be located in a magnetic field so that it doesn’t tend to rotate?

Magnet A has twice the magnetic field strength of magnet B (at equal distance) and, at a certain distance, it pulls on magnet B with a force of 50 N. With how much force, then, does magnet B pull on magnet A?

In Figure 24.15 we see a magnet exerting a force on a current-carrying wire. Does a current-carrying wire exert a force on a magnet? Why or why not?

A strong magnet attracts a paper clip to itself with a certain force. Does the paper clip exert a force on the strong magnet? If not, why not? If so, does it exert as much force on the magnet as the magnet exerts on it? Defend your answers.

A straight current-carrying wire is horizontal and oriented south to north. When a compass needle is placed below or above it, in what direction does the compass needle point?

A loudspeaker consists of a cone attached to a current carrying coil located in a magnetic field. What is the relationship between vibrations in the current and vibrations of the cone?

Will a superconducting magnet use less electric power than a traditional copper-wire electromagnet of the same field strength? Defend your answer.

A beam of electrons passes through a magnetic field without being deflected. What can you conclude about the orientation of the beam relative to the magnetic field? (Ignore any other fields.)

Can an electron at rest in a stationary magnetic field be set into motion by the magnetic field? What about the electron placed at rest in an electric field?

A proton moves in a circular path perpendicular to a constant magnetic field. If the field strength of the magnet is increased, does the diameter of the circular path increase, decrease, or remain the same?

Two charged particles are projected into a magnetic field that is perpendicular to their velocities. If the particles are deflected in opposite directions, what does this tell you about them?

A magnetic field can deflect a beam of electrons, but it cannot do work on the electrons to change their speed. Why?

Inside a laboratory room there is said to be either an electric field or a magnetic field, but not both. What experiments might be performed to establish what kind of field is in the room?

Residents of northern Canada are bombarded by more intense cosmic radiation than residents of Mexico. Why is this so?

Why do astronauts keep to altitudes beneath the Van Allen radiation belts when walking in space?

What changes in cosmic-ray intensity at Earth’s surface would you expect during periods in which Earth’s magnetic field passed through a zero phase while undergoing pole reversals?

In a mass spectrometer (see Figure 34.14), ions are directed into a magnetic field, where they curve and strike a detector. If a variety of singly ionized atoms travel at the same speed through the magnetic field, would you expect them all to be deflected by the same amount, or would different ions be bent different amounts? Defend your answer.

If you had two bars of iron—one magnetized and one unmagnetized—and no other materials at hand, how could you determine which bar was the magnet?

Will a pair of parallel current-carrying wires exert forces on each other?

What is the magnetic effect of placing two wires with equal but oppositely directed currents close together or twisted about each other?

Your study buddy claims that an electron always experiences a force in an electric field, but not always in a magnetic field. Do you agree? Why or why not?

A “dip needle” is a small magnet mounted on a horizontal axis so that it can swivel up or down (like a compass turned on its side). Where on Earth will a dip needle point most nearly vertically? Where on Earth will it point most nearly horizontally?

In what direction would a compass needle point, if it were free to point in all directions, when located near Earth’s north magnetic pole in Canada?

What is the net magnetic force on a compass needle? By what mechanism does a compass needle align with a magnetic field?

Your friend says that, when a compass is taken across the equator, it turns around and points in the opposite direction. Your other friend says that this is not true, that people in the Southern Hemisphere use the south magnetic pole of the compass to point toward the nearest pole. You’re on; what do you say?

A cyclotron is a device for accelerating charged particles to high speed as they follow an expanding spiral-like path. The charged particles are subjected to both an electric field and a magnetic field. One of these fields increases the speed of the charged particles, and the other field causes them to follow a curved path. Which field performs which function?

A magnet can exert a force on a moving charged particle, but it cannot change the particle’s kinetic energy. Why not?

A beam of high-energy protons emerges from a cyclotron. Do you suppose that there is a magnetic field associated with these particles? Why or why not?

When a current is passed through a helically coiled spring, the spring contracts as if it’s compressed. What’s your explanation?