Electromagnetism

Multiple Choice

Which of the following statements is true?

• All conductors are magnetic materials.

• All metals are magnetic materials.

• All materials that can be electrically charged are magnetic materials.

• All materials that can affect the direction of a compass needle are magnetic materials.          

Multiple Choice

A soft magnetic material can be easily magnetised and retains its magnetism longer.

• TRUE

• FALSE

Multiple Choice

Which material is commonly used as an electromagnet?

• Copper

• Steel

• Iron

• Nichrome

Multiple Choice

How are electromagnets different from permanent magnets?

• magnets can be turned on/off

• you can turn an electromagnet on/off

• magnets are more powerful

• magnets have a North and South pole

Multiple Choice

What is true about electricity and magnetic fields?

• Electricity is needed to create any magnet.
• Electricity always creates a magnetic field.
• Electricity is stronger than a magnetic field.
• Electricity prevents magnetic fields from occurring.

Multiple Choice

When using the Right-Hand Grip Rule around a current-carrying wire, the thumb represents the _____.

• North pole

• motion

• current direction

• magnetic field direction

Multiple Choice

When running a current through a wire, what do the blue lines represent?

• The wire spinning

• A magnetic field that was created

• Electrons leaving

• Electricity

Multiple Choice

Which diagram represents the direction of the magnetic field around a straight wire carrying a current out of the page?

• A

• B

• C

• D

Multiple Choice

The diagram shows a magnetic field around a current flowing out of this screen. The _____ has been drawn WRONGLY.

• current direction

• magnetic field direction

• distance between field lines

• symbol for the current

Multiple Choice

When using the Right-Hand Grip Rule for an iron bar placed in a d.c. solenoid, the thumb represents the _____.

• North pole

• motion

• current direction

• magnetic field direction

Multiple Choice

A coil with a current is shown above. In the center of the coil, a magnetic field points-

• to the right

• to the left

• upward

• downward

Multiple Choice

The diagram shows a coil connected to a battery and a switch. Two unmagnetised iron bars hang freely near opposite ends of the coil.

What happens to the iron bars when the switch is closed?

• Both X and Y move away from the coil.

• Both X and Y move towards the coil.

• X moves towards the coil, Y moves away from the coil.

• Y moves towards the coil, X moves away from the coil.

Multiple Choice

What is the main function of a circuit breaker in an electrical circuit?

• To increase voltage

• To prevent overcurrent and protect the circuit

• To store electrical energy

• To convert AC to DC

Multiple Choice

What is a common advantage of using circuit breakers over fuses?

• Circuit breakers are single-use only

• Circuit breakers can be reset after tripping

• Circuit breakers are less expensive

• Circuit breakers are slower to operate

Multiple Choice

Explain how a circuit breaker interrupts the flow of current during a fault condition.

• It melts a wire to break the circuit

• It opens its contacts to stop current flow

• It increases resistance to reduce current

• It reverses the current direction

Multiple Choice

When applying the Fleming's Left-Hand Rule, X represents the _____.

• North pole

• current direction

• magnetic field direction

• magnetic force direction

Multiple Choice

The diagram shows that __________.

• like currents attract

• like currents repel

• unlike currents attract

• unlike currents repel

Multiple Choice

The diagram shows a beam of electrons about to enter a magnetic field.

The direction of the magnetic field is into the page.

What will be the direction of the deflection, if any, as the beam passes through the field?

• No deflection

• Out of the page

• Towards the top of the page

• Towards the bottom of the page

Multiple Choice

Which of the following shows the correct magnetic field pattern?

Multiple Choice

The proton enters the magnetic field and moves __________.

• up in a straight path

• down in a straight path

• up in a curved path

• down in a curved path

Multiple Choice

When the electric current in wire XY is in the direction shown, there is an upward force on the wire.

If the north and south poles of the magnet exchange positions, in which direction will the force on the wire act?

• downwards

• upwards

• to the left

• to the right

Multiple Choice

A current-carrying coil in a magnetic field experiences a turning effect.

How can the turning effect be increased?

• increase the number of turns on the coil

• reduce the size of the current

• reverse the direction of the magnetic field

• use thinner wire for the coil

Multiple Choice

When the coil is part of a d.c. motor, what must be connected directly to X and Y?

• d.c. supply

• slip rings

• soft-iron core

• split-ring commutator

Multiple Choice

A simple DC electric motor is fitted with a coil that rotates in a magnetic field. A commutator connects the power supply to the coil.

What is the purpose of the commutator?

• It converts AC into DC in the coil.

• It prevents the current from becoming too great, because the coil has a low resistance

• It reverses the direction of the current in the coil after every 180° rotation of the coil

• It switches the current off momentarily after every 90° rotation of the coil