physics chapters 24 & 25. true or false: magnetic field lines form closed loops. answer: true
TRANSCRIPT
Physics Chapters 24 & 25
True or False: Magnetic field lines form closed loops.
Answer: True
Which of these materials are used to make permanent magnets:
a) neodymiumb) gadoliniumc) ALNICO Vd) all of the above
Answer: d
True or false: Electromagnets are useful because they can easily be turned on and off.
Answer: T
True or False: When a magnet is allowed to swing freely, it comes to rest aligned in the north-south direction.
Answer: True
True or false: In a motor, mechanical energy is used to produce electric current.
Answer: F - generator
A small magnet mounted so it is free to turn
a) galvanometerb) compass
Answer: b
True or False: Hans Christian Oersted discovered that electric current creates a magnetic field.
Answer: True
True or false: The iron core is included in an electromagnet because it is a good conductor.
Answer: F – the iron core is included because it is easily magnetized and thereby enhances the magnetic field of the coil.
True or False: Increasing the current in a wire increases the magnetic field around the wire.
Answer: True
True or False: The magnetic field strength of a magnet is weakest at the poles.
Answer: False
An electromagnet is a
a) temporary magnetb) permanent magnet
Answer: a
True or false: Voltage can be reduced with a step-up transformer.
Answer: false – step-down transformer
True or False: Increasing the number of loops of wire in an electromagnet increases the strength of its electric field.
Answer: True
True or False: Magnets may be monopoles.
Answer: False
True or false: An electromagnet consists of a current-carrying wire coil surrounding an iron core.
Answer: T
Having two distinct and opposite ends
a) magnetic fluxb) polarization
Answer: b
What is a vector quantity that exists in a region of space where a magnetic force occurs?
a) magnetic fieldb) magnetic flux
Answer: a
True or false: Maglev is short for magic levitating train
Answer: false – magnetic levitating train
True or false: Magnetic field lines show the direction and shape of the magnetic field around a magnet.
Answer: T
What does a transformer transform?
a) voltageb) charge
Answer: a
A magnet created when current flows through a wire coil
a) solenoidb) electromagnet
Answer: b
A group of neighboring atoms that have their magnetic fields aligned in the same direction
a) polarizationb) domain
Answer: b
True or False: Michael Faraday discovered that changing magnetic fields create electric current.
Answer: True
A device to measure very small currents
a) galvanometerb) electromagnet
Answer: a
True or False: The earth’s geographical north pole is near its magnetic south pole.
Answer: True
True or false: Magnetic forces or fields are produced by stationary electric charges.
Answer: F
True or False: Magnetic field lines point from south to north.
Answer: False
True or false: Motors and generators both use an electromagnet to change energy from one form to another.
Answer: T
True or false: In a step-down transformer, the primary coil has more loops than the secondary transformer.
Answer: T
True or false: Moving magnets produce electric forces or fields.
Answer: T
True or false: Junk yard electromagnets work because current is flowing through a wire coil.
Answer: T
A long coil of wire consisting of many loops
a) solenoidb) galvanometer
Answer: a
True or false: In a generator, electrical energy is used to produce mechanical energy.
Answer: F - motor
True or false: Electricity and magnetism are two aspects of the same force.
Answer: T
Swiping your credit card allows a magnetic strip on the back to pass a wire coil. What principle explains this process?
a) Electric current creates a magnetic field.
b) A changing magnetic field produces an electric current.
Answer: b
True or False: Like poles attract and opposites repel.
Answer: False
True or false: Generators produce electrical current by placing a wire coil in a changing magnetic field.
Answer: T
The number of magnetic field lines passing through a surface
a) magnetic fluxb) domain
Answer: a
Maglev trains can achieve such high speeds because they are
a) floating on a cushion of airb) aerodynamicc) both
Answer: c