Topic 4.4: Induction (HL) Questions

Draw a labelled diagram of a simple transformer.

State Faraday's law of electromagnetic induction.

An ideal transformer steps 230 V (rms) down to 23 V (rms). The secondary delivers a current of 0.50 A.
What current is drawn by the primary coil?

A rod of length 0.50 m moves at 2.0 m s⁻¹ perpendicular to a 0.40 T field, inducing an emf ε₀. If the rod's speed is then doubled to 4.0 m s⁻¹ (everything else unchanged), the new emf is…

Electrical energy is transmitted over long distances at very high voltage. Why does this reduce the energy wasted in the transmission cables?

The north pole of a bar magnet is pushed toward a flat coil. Viewed from the magnet's side, the induced current in the coil flows so that…

A flat loop of area 0.020 m² sits in a uniform field of flux density 0.60 T. The normal to the loop makes an angle of 60° with the field. What is the magnetic flux through the loop?

A simple AC generator has a coil of 150 turns, each of area 0.020 m², rotating with an angular frequency of 60 rad s⁻¹ in a uniform magnetic field of flux density 0.30 T. (a) Determine the peak emf of the generator. (b) State one change to the coil that would increase the peak emf.

A straight conducting rod of length 0.60 m slides along two horizontal rails at a constant 5.0 m s⁻¹. A uniform magnetic field of flux density 0.25 T is directed vertically, perpendicular to the plane of the rails. (a) Determine the emf induced across the rod. (b) Explain, in terms of magnetic flux, why an emf is induced even though the field is constant.

The mains supply in a certain country has an rms voltage of 120 V.
(a) Determine the peak voltage of this supply.
(b) State why appliances are labelled with the rms voltage rather than the peak voltage.

An AC generator produces an output of period 12 ms. The angular speed of the coil is then reduced to three-quarters of its original value, with nothing else changed.
What is the new period of the output?

A single flat circular loop of radius 0.12 m is placed in a uniform magnetic field of flux density 0.45 T. The loop is tilted so that the normal to its plane makes an angle of 35° with the field.

Determine the magnetic flux through the loop.

A heating element rated at 1100 W is connected to an AC supply whose rms voltage is 230 V.
(a) Determine the rms current in the element.
(b) Hence determine the peak current drawn by the element.

A coil rotating in a uniform field generates a sinusoidal emf with a peak value of 12 V and a period of 20 ms. The angular speed of the coil is now doubled.

(a) Determine the new peak emf.
(b) Determine the new period.
(c) State how the frequency of the alternating emf changes.

Coil P has 120 turns and the flux through it changes at 0.050 Wb s⁻¹. Coil Q has 40 turns and the flux through it changes at 0.20 Wb s⁻¹.

(a) Calculate the emf induced in each coil.
(b) Compare the two emfs and explain, in terms of Faraday's law, why they differ in the way they do.

A rectangular coil rotates at a steady rate in a uniform magnetic field, producing a sinusoidal emf.
(a) State the orientation of the coil relative to the field at the instant the induced emf is a maximum.
(b) Explain, in terms of magnetic flux, why the emf is zero when the plane of the coil is perpendicular to the field.

A rectangular coil rotates at constant angular speed in a uniform magnetic field. The induced emf is at its MAXIMUM at the instant when…

The flux through each turn of a 30-turn coil rises steadily from 0 to 0.012 Wb in 0.090 s. The magnitude of the emf induced in the coil is…

A rectangular coil rotates in a uniform magnetic field, generating a sinusoidal emf of peak value ε₀.
Which single change increases the maximum induced emf?

Outline Lenz's law.