test 2 Flashcards
1.To create an electromagnet,
A) Use electric heat to force the magnetic domains to rearrange themselves into a random pattern.
B) Stroke a nonmagnetic metal with a magnet.
C) Place a magnetic field parallel to the electrostatic field.
D) Hang magnetite by a string and allow it to swing freely.
E) Wrap a coil of insulated wire around an iron bar and pass an electric current through the wire.
2.Magnetism
A) Involves the fact that the Earth’s geographic and magnetic poles are in exactly the same location in each hemisphere.
B) Was discovered when the Greeks noticed that magnetite always aligned itself in a north and south direction.
C) Is believed to result from the spinning action of the nucleus of the atom.
D) Interacts with electricity because the electron’s electrostatic field points outward.
E) Is strongest in atoms with outer shells of electrons that are evenly divided in their direction of spin.
3.In a magnetic material,
A) That has magnetic domains all aligned the effects cancel, making the material nonmagnetized.
B) Such as iron, scientists believe that the 12 electrons in the third shell are evenly joined together in their direction of spin, canceling other shells’ magnetic fields.
C) That is exposed to an external magnetic force the magnetic domains subtract and scatter in a random pattern, making the material magnetized.
D) Where only some of the magnetic domains are pointing in the same direction, the magnetic field is weaker.
E) Such as chlorine, scientists believe it is magnetic because of an even number of spinning electrons in the second shell.
4.The strength of an electromagnetic field is
A) Decreased by an increase in current flow.
B) Increased by a decrease in the number of turns in the coil.
C) Decreased by the placement of an iron core inside the coil.
D) Determined by multiplying the voltage times the coil diameter.
E) Determined by the magnitude of the magnetomotive force (mmf).
5.The magnetic field
A) Around a current-carrying conductor becomes stronger as the distance from the conductor increases.
B) Created by a straight piece of wire is weaker than that created by forming loops of wire.
C) Of an electromagnet is always directed from its south pole to its north pole.
D) Is illustrated by lines of force called flux lines that extend out into space from the magnet’s midpoint between poles in a spiral pattern.
E) Causes the electrical contacts of the magnetic reed relay to open.
6.Flux lines
A) Can combine and cross one another.
B) Of a magnet extend out into space, leaving the magnet’s south pole and re-entering its north pole.
C) That are farther from the magnet and wider apart indicate a stronger magnetic field.
D) Always curve around through the body of the magnet to form complete loops.
E) Tend to repel one another when unlike poles are near each other.
7.Magnetic poles that are ___________ will ____________ each other when those poles are near each other.
A) Opposite, cancel B) Opposite, repel C) Alike, repel D) Alike, attract E) Heated, magnetize
8.A permanent-magnet loudspeaker
A) Cannot be used as a microphone.
B) Operates on the interaction of five magnetic fields.
C) Utilizes both a temporary magnet and an electromagnetic coil.
D) Uses current that is generated by a light wave passing through an optical coil.
E) Has a cone that moves back and forth in relation to the varying current of the original sound.
9.The left-hand rule for electromagnetism in a wire states that
A) If you wrap the fingers of your left hand around the wire with your thumb pointing in the direction of the current flow, your fingers will be wrapped in the direction of the magnetic field.
B) If you wrap the fingers of your left hand around the wire with your thumb pointing in the direction of the electrostatic field, your fingers will point in the direction of current flow.
C) If you wrap the fingers of your left hand around the wire with your thumb pointing in the direction of the south magnetic pole, your fingers will point in the direction of the highest resistance.
D) If you wrap the thumb of your left hand around a coil in the opposite direction of the current flow, your fingers will be pointed in the direction of the electrostatic field.
E) If you wrap wire around the fingers of your left hand in the direction of the magnetic field, your thumb will point opposite to the direction of current flow.
10.The recording head of a tape recorder is actually a(an)
A) Diaphragm. B) Electromagnet. C) Microphone. D) Permanent magnet. E) Reed relay.
