Chapter 24 Physics: Magnetism – Flashcards
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The source of all magnetism is
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moving electric charge.
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The force that acts between a pair of magnetic poles depends on
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magnetic pole strength. separation distance.
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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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Whereas electric charges can be isolated, magnetic poles
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cannot
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Refrigerator magnets are typically
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short range
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If you break a bar magnet in half you'll
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have two magnets
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Surrounding every magnet is
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an electric field. a magnetic field.
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Magnetic fields are produced by
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all moving electrical charges.
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Surrounding every moving electron is
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a magnetic field. an electric field.
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Magnetism is due to the motion of electrons as they
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move around the nucleus. spin on their axes.
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The conventional direction of magnetic field lines outside a magnet are from
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north to south.
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Magnetic field strength about a magnet is strongest where magnetic field lines are
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closer together
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An iron rod becomes magnetic when
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the net spins of many of its electrons are aligned.
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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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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 compass needle in a magnetic field
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may experience a pair of torques.
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Magnetic domains normally occur in
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iron
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In the atoms of most materials the fields of individual electrons
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cancel one another.
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Wood does not have magnetic properties because it contains no
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magnetic domains.
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To weaken a bar magnet
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drop it on a hard surface. put it in hot flames. whack it with a hammer.
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Several paper clips dangle from the north pole of a magnet. The induced pole in the bottom of the lowermost paper clip is a
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north pole.
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Magnetic field lines about a current-carrying wire
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circle the wire in closed loops.
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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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When a current-carrying wire is bent into a loop, its magnetic field inside the loop
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becomes concentrated.
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A beam of electrons passing through a magnetic field experiences maximum deflection if the direction of the beam is
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perpendicular to the field lines.
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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 current-carrying loop of wire experiences no tendency to rotate in a magnetic field when
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no 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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Place an iron rod inside a current-carrying coil of wire and you
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increase the strength of the electromagnet.
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A superconducting magnet uses
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superconducting coils.
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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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Compared to the huge force that attracts an iron tack to a strong magnet, the force that the tack exerts on the magnet is
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equally huge.
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Into which stable force field can a proton be placed at rest without being acted upon by a force?
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magnetic field
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The direction of the force exerted on a moving charge in a magnetic field is
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at right angles to the direction of the motion.
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The force on an electron moving in a magnetic field will be least when its direction is
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the same as the magnetic field direction.
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When an electron passes through the magnetic field of a horseshoe magnet, the electron's
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direction is changed.
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The force exerted on an electron moving in a magnetic field is maximum when the electron moves
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perpendicular to the magnetic field.
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The force a magnetic field exerts on a current-carrying wire is maximum when the wire is oriented
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perpendicular to the magnetic field.
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A current-carrying wire in a magnetic field
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may be deflected. may experience a force.
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An electron beam directed through a magnetic field
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may experience a force. may be deflected.
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No net force acts on a loop of wire in a magnetic field when
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no current is in the loop. no magnetic field lines pass through the loop.
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If a magnet produces a force on a current-carrying wire, the wire
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produces a force on the magnet.
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A galvanometer indicates
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a flow of electrons.
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A galvanometer can be calibrated to measure
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electric current. electric voltage.
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Although a magnet can change the direction of travel of an electron beam, it cannot change its
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speed kinetic energy.
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Which force field can increase a moving electron's speed?
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electric field
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Which force field can accelerate an electron?
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electric field magnetic field
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Over geologic history the Earth's magnetic field
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has reversed direction many times.
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Solar winds headed in Earth's direction are deviated mainly by
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Earth's magnetic field.
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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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Cosmic rays penetrate your body when
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outdoors. in mountainous regions. safely in your home.
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Earth's magnetic field is
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protective to life on Earth.
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Pigeons navigate primarily by
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magnetic sensors in their heads.
