review: magnetic fields and electromagnetic induction

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