The force that acts on an electron traveling in a magnetic field is
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perpendicular in direction to the magnetic field
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The fundamental rule for the attraction and repulsion of magnets is that
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like poles repel each other while opposite poles attract
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Magnetic domains are composed of clustered
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aligned iron atoms
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The cosmic rays deflected most by Earth's magnetic field are above the
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equator
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The force that acts on a current-carrying wire placed in a magnetic field is
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perpendicular in direction to the magnetic field
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The magnetic field about a straight length of current-carrying wire is
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circular in shape
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The magnetic field about Earth takes a shape
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similar to that of an interior bar magnet
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When an iron rod is placed inside a current-carrying coil of wire
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the coil becomes a stronger electromagnet
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The source of a magnetic field is a moving
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electron
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Compared with a simple galvanometer, an electric motor is
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much the same with small modifications
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The figure shows the path of a charged particle moving in a magnetic field directed into the screen.
What is the particle's charge?
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negative
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What happens when Dr. Hewitt places a current- carrying wire between the poles of the magnet for the first time?
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The wire jumps down
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What happens when Dr. Hewitt turns the magnet around and places the current-carrying wire between the poles of the magnet for the second time?
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The wire jumps up
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What kinds of appliances work on the principle of deflection of a current-carrying wire in a magnetic field?
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electric motor
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What happens when a switch is closed in a circuit that contains a battery and a wire that is placed between the poles of a magnet?
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The wire will either bend up or down between the poles of the magnet due to the force of the magnetic field
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What happens to the shape of a wire that is part of a circuit with a battery when the switch is closed and the battery voltage is increased?
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The wire bends more than it did before
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What happens to the shape of a wire that is part of a circuit with a battery when the switch is closed and the direction of the current is reversed in the wire?
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The wire will bend the same amount but in the opposite direction
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Is it correct to say that an electric motor extends the physics that underlies a galvanometer? Why?
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Yes. The deflection forces are the same, but the direction of current in the motor is reversed cyclically
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At the micro level, what is the difference between an unmagnetized iron nail and a magnetized iron nail?
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In an unmagnetized nail, the magnetic domains have a random orientation so that the net magnetism adds to zero. In a magnetized nail, many of the magnetic domains are aligned
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Why are the magnetic fields of superconducting magnets often stronger than those of conventional magnets?
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Conventional magnets based on iron have a maximum magnetization that occurs when all of the domains are aligned. This saturation magnetization is weaker than the magnetic field of superconducting coils
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What produces a magnetic field?
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Electric charges in motion
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Why does a piece of iron in a current-carrying loop increase the magnetic field strength?
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The electromagnetic field of the current-carrying loop is amplified because it aligns the domains in the iron
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Why is the magnetic field strength greater inside a current-carrying loop of wire than about a straight section of wire?
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The magnetic field of each segment of wire in the loop, due to electrons moving in the wire, adds together inside the loop, thereby making the field become bunched-up
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What is a galvanometer called when it has been calibrated to read current? When it has been calibrated to read voltage?
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Ammeter, voltmeter
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What is the source of the magnetic force?
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Electric charges in motion are the sources of magnetic forces
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Which of the following are creatures that are known to harbor tiny magnets within their bodies?
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Bacteria, pigeons, bees, wasps, monarch butterflies, and sea turtles
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What are magnetic pole reversals?
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The poles of the Earth's magnetic field undergo reversals
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How is the rule for the interaction between magnetic poles similar to the rule for the interaction between electrically charged particles?
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Like poles repel, unlike poles attract, and the force is proportional to the inverse square of the distance between two poles
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When do cosmic rays penetrate your body?
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All the time
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How does magnetic field strength relate to the closeness of magnetic field lines about a bar magnet?
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The field strength is stronger where the field lines are closer
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The force between electrically charged particles depends on the magnitude of each charge, their separation distance, and what else?
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Their motion
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How is the magnetic force on a particle moving in a magnetic field different from gravitational and electric forces
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Gravitational and electric forces act along the line connecting two interacting objects, whereas magnetic forces are perpendicular to the motion of the particle and the magnetic field
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The magnetic fields of a pair of nearby magnets can
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add or subtract by vector rules
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Biomagnetism has been detected in
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all of the above
(humans, wasps, pigeons, bacteria)
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No net force acts on a loop of wire in a magnetic field when
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both of these
(no current is in the loop, no magnetic field lines pass through the loop)
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A current-carrying coil of wire is
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an electromagnet
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The source of all magnetism is
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moving electric charge
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Cosmic rays penetrate your body when
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all of the above
(in mountainous regions, outdoors, safely in your home)
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The intensity of cosmic rays bombarding the Earth's surface is most at the
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poles
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The shape of a magnetic field surrounding a current-carrying conductor is
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circular
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A beam of electrons can pass through a magnetic field without being deflected if the direction of the beam is
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parallel to the field lines
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A galvanometer indicates
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a flow of electrons
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Magnet A has twice the magnetic field strength of Magnet B and at a certain distance pulls on magnet B with a force of 100 N. The amount of force that magnet A exerts on magnet B is
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exactly 100 N
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When current reverses direction in a wire, the surrounding magnetic field
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also reverses direction
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Like kinds of magnetic poles repel while unlike kinds of magnetic poles
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attract
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Surrounding every moving electron is
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both of these
(an electric field, a magnetic field)
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The end of a compass needle that points to the south pole of a magnet is the
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north pole
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A beam of electrons can pass through a magnetic field without being deflected if the direction of the beam is
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parallel to the field lines
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