Physics Magnetism Test
What is the most common source of mechanical energy used in commercial power plants?
Running water
Pushing a magnet through an electric field requires work. The greater the electric field,
the stronger the force required to push the magnet through the electric field
A magnetic field around a current-carrying wire forms
Concentric circles around the wire
How are electric and magnetic field waves oriented relative to each other in an electromagnetic wave?
Electric and magnetic field waves are oriented at 90 degree angles relative to each other.
Magnetic fields are produced by
Electric currents
A device that converts electric energy into mechanical energy is a(n)
Electric motor
The magnetism of a piece of magnetized iron can be weakened by
Heating and hammering the iron
What material was used to make the first compass?
Lodestone
How does a compass indicate direction?
A compass aligns with Earth's magnetic field just as iron fillings align with the field of a bar magnet, the N pole of the compass points toward Earth's Geographic North Pole
In an AC generator, the magnitude of the current produced
All of the above (depends on the orientation of the loop in a magnetic field, is zero when the loop is perpendicular to the magnetic field, varies with time)
Magnetic force
All of the above (is a field force, is strongest near a magnet's poles, acts at a distance)
Magnetic fields exist
All of the above (near a magnet, farther away from a magnet, within a magnet)
A compass needle naturally points toward
All of the above (the geographic North Pole, the S pole of a magnet, Earth's North Magnetic Pole)
Where is Earth's magnetic N pole located?
Antarctica
When a wire is moving perpendicular to a magnetic field, the force on the charges is
At a maximum
A transformer changes
Both the amperage and the voltage of an electric current
In addition to running water, what are there other sources of mechanical energy used by generators to generate electrical energy?
Burning coal, nuclear fission, wind, hot water from geysers (geothermal), or solar power.
Where are Earth's magnetic poles located?
Canada and Antarctica
When an iron rod is inserted into a solenoid's center, the magnetic field produced by the current in the loops
Causes alignment of the domains in the iron
A current-carrying wire is perpendicular to the surface of a table. The direction of current is toward the floor. What is the direction of the magnetic field as viewed from above?
Clockwise
What instrument is used to trace the direction of a magnetic field
Compass
The magnetic field strength of a magnet
Decreases as distance from the magnet increases
Light travels as
Electromagnetic waves
A potential difference causes
Electrons to move from the negative terminal to the positive terminal of a battery.
What do galvanometers use to measure the current in a circuit?
Galvanometers measure the current in a circuit using the magnetic field produced by the curent in a coil
How are generators different from electric motors?
Generators convert mechanical energy to electrical energy, whereas electric motors convert electric energy to mechanical energy
What causes the magnetic properties of bar magnets?
In the material that a bar magnet is composed of, the magnetic fields of the electrons do not all cancel, so each atom has its own magnetic field. The domains in the bar magnet are aligned more in a common direction.
Transforms can
Increase or decrease voltage
What are two ways to increase the strength of the magnetic field of a solenoid?
Increasing the current or inserting an iron core would increasing the magnetic field strength of a solenoid
The strength of a magnetic field of a solenoid can be increased by
Increasing the number of loops on the solenoid
The strength of the magnetic field of a solenoid can be increased by
Inserting an iron rod
How can the magnetic field around a permanent magnet be determined?
It can be determined with a compass. The direction of the magnetic field is defined as the direction in which the north pole of a compass needle points at that location
In a magnetized substance, the domains
Line up more uniformly in one direction
Magnetically soft substances
Lose their magnetism more easily than others
What do magnetic field lines that are close together indicate?
Magnetic field lines that are close together indicate a strong magnetic field
Where is Earth's magnetic S pole located?
Northeastern Canada
Both electric and magnetic fields in an electromagnetic wave are
Perpendicular to the direction that the wave travels
Which orientation characterizes the magnetic domains in an unmagnetized piece of iron?
Random
Like magnetic poles always
Repel each other
What causes a compass needle to point to geographic north?
The compass needle aligns with Earth's magnetic field.
In an AC generator, when charges experience the most rapid change in magnetic force,
The current increases
Describe the orientation of the domains inside an unmagnetized piece of iron.
The domains are randomly oriented in an unmagnetized piece of iron.
What is the relationship between the electric field and the magnetic field in an electromagnetic wave?
The electric and magnetic fields are perpendicular to each other and to the direction the EM wave travels. As the wave moves along, the changing electric and magnetic fields regenerate each other.
What is the relationship between the current in an electromagnet and its magnetic field?
The greater the current, the stronger its magnetic field.
If the head of an iron nail touches a magnet, the nail will be magnetized. If the nail touches the north pole of the magnet, what kind of pole is at the point of the nail? Explain.
The head of the magnetized nail, which is touching the north pole of the magnet, will be a south pole. Otherwise, it would be repelled by the magnet. The tip of the nail will be a north pole.
How does inserting an iron rod through the center of a solenoid increase the strength of its magnetic field?
The magnetic field of the rod adds to the coil's field, creating a stronger magnet than the solenoid alone.
A bar magnet is suspended and allowed to rotate freely. If the magnetic field of Earth is considered to be equivalent to that of a large bar magnet, which pole of the suspended magnet would point toward the Geographic North Pole of Earth?
The north (N) pole would point to the Geographic North Pole of the Earth
What determines the strength of the magnetic field?
The strength of the magnetic field depends on the material from which the magnet is made and the degree to which it is magnetized
A solenoid is standing on its end on a table. The direction of current is counterclockwise. Which end of the solenoid is a N pole?
The top
An electric motor and a generator are similar in that both
Transform energy into a different form
An example of a naturally occurring magnetic rock is a
lodestone
When a wire is moving parallel to a magnetic field,
no current is induced in the wire
The north pole of one magnet will be attracted to
the middle of a magnet
When a charge moves along or opposite the direction of the magnetic field lines, the magnetic force is
zero
What is a galvanometer?
A galvanometer is an instrument that measures the amount of current in a circuit.
What is a generator?
A generator is a device that uses electromagnetic induction to convert mechanical energy to electric energy.
What is a magnetic pole?
A magnetic pole is an area of a magnet where the magnetic force appears to be the strongest
What is a solenoid
A solenoid is a long, wound coil of insulated wire.
What is a transformer?
A transformer is a device that can change one alternating current voltage to a different alternating current voltage.
Generators convert
Mechanical energy to electrical energy
The strength of a magnetic field created by current in a wire can be increased by
Wrapping the wire into a coil