Magnetism and Its Uses

How could the output voltage of an electrical generator be increased?

• by reducing the generator’s rotational speed

• by reducing the mechanical work put into the generator

• by increasing the resistance of the coils in the generator

• by increasing the number of coils in the generator’s electromagnet

How does a step-down transformer alter the amount of voltage from a power line to a building?

• It increases output voltage by increasing the number of wire turns in the secondary coil.

• It decreases output voltage by decreasing the number of turns in the secondary coil.

• It increases output voltage by decreasing the number of wire turns in the secondary coil.

• It decreases output voltage by increasing the number of turns in the secondary coil

Two magnets are stuck end to end by a magnetic force. Which statement best describes these magnets?

• The north poles of the magnets are attracted to each other.

• The south poles of the magnets are attracted to each other.

• The south pole of one magnet is repelled by the north pole of the other magnet.

• The north pole of one magnet is attracted to the south pole of the other magnet.

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Which action will have the least effect on the strength of an electromagnet?

• changing the amount of current

• changing the current’s direction

• changing the number of wire loops

• changing the size of the metal core

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In cars with electric door locks, electromagnets allow the doors to be locked and unlocked at the push of a button. Why is an electromagnet used for this kind of door lock?

• Using electromagnets conserves electricity

• Using electromagnets prevents static electric shock.

• Electromagnets can easily be turned off.

• Electromagnets can attract metals or nonmetals.

Which statement best describes the magnetic orientation of the two magnets shown in the diagram above?

• B and C are both north-seeking poles

• B and C are both south-seeking poles

• A and C are both north-seeking poles

• A and C are both south-seeking poles.

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What is the purpose of a transformer?

• Change the voltage of alternating current

• change the resistance of direct current

• convert potential to kinetic energy

• convert mechanical energy to electrical energy

If the north poles of two bar magnets are brought together, which is true?

• The two north poles will repel each other.

• The two north poles will attract each other.

• No force will be experienced between the two magnets

• One north pole will become a south pole due to the interactions

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A device that increases or decreases voltage in a power line is a ___.

• commutator
• generator
• motor
• transformer

Current that does NOT reverse direction is called ___.

• alternating
• direct current
• circuit current
• magnetic current