Quest 3 - Electromagnetic Induction

What did Michael Faraday discover about electromagnetic induction?

• A stationary magnetic field induces current

• A changing magnetic flux induces an electromotive force (EMF)

• Current is only induced in a closed circuit

• Electromagnetic induction is not possible without a battery

Faraday's Law states that the induced EMF in a closed loop is proportional to:

• The square of the magnetic field

• The rate of change of the magnetic flux

• The current passing through the loop

• The resistance of the loop

Lenz's Law states that the induced EMF will always act to:

• Oppose the change in magnetic flux

• Increase the rate of change of flux

• Remain constant regardless of external conditions

• Generate current in the same direction as the applied magnetic field

What happens when a magnet is moved towards a coil of wire?

• No current is induced

• A current is induced in a direction that opposes the magnet’s motion

• The current always flows in the same direction

• The coil generates an electric field that repels the magnet

If the magnetic flux through a coil is constant, what is the induced EMF?

• Maximum

• Zero

• Increasing exponentially

• Equal to the resistance of the coil

The unit of magnetic flux is:

• Tesla (T)

• Weber (Wb)

• Volt (V)

• Henry (H)

The formula for Faraday's Law is given by:

• E = - dΦ/dt

• E = BIL sinθ

• E = IR

• E = qE

What is the primary cause of motional EMF?

• A stationary conductor in a uniform magnetic field

• A conductor moving through a magnetic field

• A high resistance in a circuit

• A constant electric field

The expression for motional EMF is:

• E = BvL sinθ

• E = BIL

• E = IR

• E = q/m

In an ideal transformer, the voltage ratio between the primary and secondary coils is given by:

• Vs/Vp = Ns/Np

• Vs/Vp = Np/Ns

• Vs/Vp = Is/Ip

• Vs/Vp = Bs/Bp