UEEEL0021 Revision

Multiple choice. Magnetic screening is the use of a screen:

• made of high permeability magnetic material to protect electric circuits from magnetic fields

• made of high permeability magnetic material to connect electric circuits to magnetic fields

• made of low permeability magnetic material to protect electric circuits from magnetic fields

• made of low permeability magnetic material to connect electric circuits to magnetic fields

Multiple choice. What is magnetic shielding?

• magnetic attraction

• magnetic force

• magnetic screening

• magnetic strength

Choose all that apply. Which of the following it true of magnetic screening?

• It is usually sheet metal

• It is usually fibre material

• It is a chemical solution to a problem

• It is a mechanical solution to a problem

• It solves a problem associated with low frequency electromagnetic disturbance

Multiple choice. The length of a conductor and the force of a conductor are related. How are they related?

• When length increases, force decreases

• When length increases, force increases

• When length increases, force stays the same

If you increase the distance between a primary and secondary winding, what happens?

• Increasing the distance makes the force higher between conductors

• Increasing the distance makes the force lower between conductors

• Increasing the distance does not affect the force between conductors

What is an electromagnet?

An electromagnet is a type of magnet:

• where the magnetic field is produced by chemical reaction

• where the magnetic field is produced by electric current

• where the magnetic field is produced by physical force

• where the magnetic field is produced by static electricity

How does an electromagnet affect a relay switch?

• An electromagnet can only be used to open a switch contact

• An electromagnet can only be used to close a switch contact

• An electromagnet can be used to both open and close a switch contact

Choose all that apply. What produces the conversion of electrical energy into mechanical motion in electric motors?

• A transformer is used to step up voltage in a power distribution system

• A transformer is used to lower voltage in a power distribution system

• A transformer has no effect on voltage in a power distribution system

• A transformer is used to step up and step down voltage in a power distribution system

Choose all that apply. What is the electromagnetic induction process in a transformer?

• alternating current in the primary coil induces a changing magnetic field

• alternating current in the secondary coil induces a changing magnetic field

• a changing magnetic field leads to electromagnetic induction

• electromagnetic induction leads to creating a voltage in the secondary coil.

• electromagnetic induction leads to lower voltage in the primary coil.

How does the electromagnetic induction process heat up the cookware on an induction cooktop.

• the cooktop generates a rapidly changing magnetic field

• the cookware generates a rapidly changing magnetic field

• the changing magnetic field induces electric currents in the ferrous material of the cookware

• the changing magnetic field induces electromagnetic currents in the ferrous material of the cookware

• These currents create resistive heating, efficiently transferring energy directly to the cookware