Magnets and Electromagnets: Introduction to Magnetism

Which statement best describes magnetism as introduced in this section?

• A contact force that requires touching to attract objects

• A non-contact force that can attract certain materials

• A chemical force that only acts on liquids

• A gravitational force that affects all metals equally

Which list correctly identifies common magnetic materials mentioned in this section?

• Aluminium, copper, and tin

• Iron, nickel, and cobalt

• Plastic, glass, and wood

• Gold, silver, and platinum

Two north poles of bar magnets are brought close together. What happens according to the rules of magnetic poles?

• They attract because similar poles pull together

• They repel because like poles push apart

• They remain neutral with no effect

• They cancel each other and lose magnetism

A student uses a small device that always points north unless nearby magnetic materials disturb it. What is this device called?

• Voltmeter

• Compass

• Thermometer

• Barometer

Look at the bar magnet field-line diagram: field lines curve from the north end to the south end and loop around the magnet. Based on this visual, what is the term for the space around the magnet where it has an effect?

• Magnetic domain

• Magnetic field

• Electric circuit

• Gravitational field

A wire has an electric current flowing through it. Which statement applies, and what is the term for a coil of wire with current?

• The wire has no magnetic effect; a coil with current is a transformer

• The wire creates a magnetic field; a coil with current is an electromagnet

• The wire creates heat only; a coil with current is an insulator

• The wire repels gravity; a coil with current is a capacitor

Which change will directly make an electromagnet stronger according to the text?

• Using fewer coils of wire

• Decreasing the current through the coil

• Adding an iron core inside the coil

• Removing the power source

Electromagnets are used in several devices. Which option best matches a stated use from the material?

• To cool electronic components

• To lift objects and operate bells, relays, and recording equipment

• To store chemical energy in batteries

• To measure temperature in circuits

A reed switch contains two thin pieces of iron. What causes them to touch each other and close the switch?

• Heat from the circuit expands the iron until it bends together

• A nearby magnet or an electromagnet magnetises the iron so the pieces attract and meet

• Sound vibrations from a bell make the iron pieces move toward each other

• Light shining on the switch changes the iron’s resistance and makes contact

In the relay diagram, current flows in circuit 1 and the coil becomes an electromagnet. What happens next to allow electricity to flow in circuit 2?

• The iron armature is repelled and opens the contacts, breaking circuit 2

• The iron armature is attracted and moves to connect the contacts, completing circuit 2

• The coil heats up and melts the contacts, letting current pass

• The battery directly powers both circuits without any movement