Transcript Magnetism Concepts

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4.
____The polarity of an electromagnet can be
determined using the second right-hand rule.
____Current passing through a conductor is
increased from 10 A to 15 A. This decreases the
strength of the magnetic field produced by the
conductor.
____The speed of an electric motor can be
controlled by varying the amount of current
through the motor.
____Magnetic fields exit from the north poles of
magnets and enter the south poles of magnets.
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____Cathode ray tube computer monitors
and TV screens use magnets to focus and
direct particles on phosphor screens.
____The electromotive force is a force that
makes charges flow from a point of higher
potential to lower potential.
____Hans Christian Oersted discovered
that a changing magnetic field produces
an electric current.
____A current is generated when a wire is
moved parallel to a magnetic field.
____Lenz’s law applies to both motors and
generators.
____In a step-down transformer, the
current in the secondary circuit is less than
the current in the primary circuit.
 There
are four coils of wire being used as
electromagnets. They all have the same size
and are made up of the same material but
have a different number of loops. Which coil
will produce a magnetic field with the
maximum strength when the same amount
of current passes through all coils?
a.
b.
c.
d.
a coil having 10 loops
a coil having 30 loops
a coil having 25 loops
a coil having 45 loops
 Which
rule is used to find the direction of
force acting on a current-carrying wire in
a magnetic field?
a. the first right-hand rule
b. the third right-hand rule
c. the second right-hand rule
d. the fourth right-hand rule
 A/An
_____ is a magnet created when
current flows though a wire coil.
a. Solenoid
b. electric motor
c. Electromagnet
d. armature
 The
_____ is a method used to determine
the direction of a magnetic field relative
to the direction of conventional current.
a. first right hand rule
b. third right hand rule
c. second right hand rule
d. none of the above
A
uniform magnetic field of 0.25 T points
vertically downward. A proton enters the
field with a horizontal velocity of 4.0 10
m/s north. What are the magnitude and
direction of the instantaneous force exerted
on the proton as it enters the magnetic
field?
a.
b.
c.
d.
1.6
1.6
1.6
1.6
10-13 N west
10-13 N downward
10-13 N east
10-13 N to the right
 Which
rule is used to find the direction of
force produced by electromagnetic
induction?
a. First right-hand rule
b. Second right-hand rule
c. Third right-hand rule
d. Fourth right-hand rule
A
step-up transformer _____.
a. increases voltage and current
b. increases voltage and decreases current
c. decreases voltage and increases current
d. decreases voltage and current
 In
an ideal transformer, the electric
power delivered to the secondary circuit
_____ the power supplied to the primary
circuit.
a. equals
b. is greater than
c. is less than
d. is unrelated to
 Given
a wire with a current in the direction
towards you (out of the page), what can you
say about the magnetic field produced by
the wire?
a. The magnetic field lines point away from the wire.
b. The magnetic field lines point towards the wire.
c. The magnetic field lines circle clockwise around
the wire.
d. The magnetic field lines circle counter-clockwise
around the wire.
 Which
one of these statements about
electromagnetic induction is FALSE?
a. Changing the magnetic field strength through
a wire loop will induce a current.
b. Moving a wire with no current through a
constant magnetic field induces a current in
the loop.
c. Moving a magnetic field past a wire will
induce a current
d. A constant magnetic field will induce a current
in a stationary wire.
 The
two coils of a transformer MUST
_____.
a. be electrically insulated from each other
b. be wound around the same iron cores
c. have the same number of windings
d. have the same resistance
 Transformers
can change _____ with
relatively little loss of energy.
a. Magnetic fields
b. Power
c. Resistances
d. Voltages
A long coil of wire that contains many loops is
called a(n) _____.
 A group of neighboring atoms whose electrons’
magnetic fields all align in the same direction is
called a(n) _____.
 A(n) _______ is a device that converts electrical
energy into rotational kinetic energy.
 A(n) _______ is a device that converts rotational
kinetic energy into electrical energy.
