A bar magnet attached to a spring is allowed to fall vertically from rest through a simple coil of conducting wire. The potential difference (pd) across the solenoid is measured using a datalogger.
The graph shows the variation of the pd across the coil with time.
(a)
Explain the shape of the graph by
(i)
Making reference to both Faraday's and Lenz's laws.
Outline how the simple harmonic motion of the oscillations would be affected by replacing the magnet with one of equal mass but with a greater magnetic field strength.
A vertical copper rod is attached to the mass of a mass-spring system so that it can be made to oscillate with simple harmonic motion with a time period T at right angles to a uniform magnetic field.
The graph shows the variation with time t of the horizontal displacement x of the rod.
(a)
Sketch a graph to show
(i)
Variation with time t of the vertical velocity v of the rod.
[2]
(ii)
Variation with time t of the emf generated between the ends of the rod.
Conducting wire is wrapped around a circular disk of diameter 10 cm to create a loop with 145 turns. The loop is held in a constant magnetic field with field strength 0.36 T.
(d)
Determine the magnetic flux through the loop when the angle between the disk and the magnetic field is 10o.
A toy car with a magnet attached so that the North pole faces upwards is released from the top of a ramp. The car rolls down the ramp at constant speed. An emf is induced in a coil of wire as the toy and magnet pass underneath it.
The induced emf is recorded by a datalogger attached to the coil.
(a)
The graph shows the variation of induced emf.
(i)
Determine the maximum rate of change of flux linkage in the coil.
[1]
(ii)
Explain the shape of the graph between points A and B.
An electromagnetic braking system uses a metal disk, attached to the wheel of the vehicle so that they rotate together. An electromagnet is placed such that the poles are on either side of the rotating disk, but do not touch it.
When the driver applies the brakes a direct current passes through the coil of the electromagnet.
(a)
Explain with reference to appropriate laws of electromagnetic induction how this design can produce a braking effect.
Conventional braking systems use friction pads which are brought into contact with a rotating disk to slow down vehicles.
(b)
Distinguish between the electromagnetic and conventional braking systems, identifying at least two advantages and two disadvantage of the electromagnetic system.
