Chapter 18 Magnetism and its uses

Which will cause an electromagnetic solenoid to increase its strength?

• replacing the wire with an insulator inside the solenoid

• increasing the temperature surrounding the solenoid

• increasing the number of wire coils in the solenoid

• removing the iron core from the solenoid

A copper wire is connected across a constant voltage source. Which change will cause an increase in the current flowing through the wire?

• an increase in the length of the wire

• an increase in the resistance of the wire

• an increase in the diameter of the wire

• an increase in the insulation around the wire

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 could the strength of an electromagnet be increased?

• by reducing the length of the core of the electromagnet

• by using rubber material as the core for the electromagnet

• by decreasing the amount of current in the electromagnet

• by increasing the number of coils in the wires of the 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.

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

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.

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