A bar magnet of mass 250 g is suspended from the free end of a spring, as illustrated in Fig. 3.1. [Figure 3.1] The magnet hangs so that one pole is near the centre of a coil of wire. The coil is connected in series with a resistor and a switch. The switch is open. The magnet is displaced vertically and then allowed to oscillate with one pole remaining inside the coil. The other pole remains outside the coil. At time t = 0, the magnet is oscillating freely as it passes through its equilibrium position. At time t = 6.0s, the switch in the circuit is closed. The variation with time t of the vertical displacement y of the magnet is shown in Fig. 3.2. [Figure 3.2]

1. (a)(i)the frequency f, f = ........................................................................ Hz [2][2]
2. (a)(ii)the energy of the oscillations during the time t = 0 to time t = 6.0s. energy = ....................................................................... J [3][3]
3. (b)(i)State Faraday's law of electromagnetic induction.[2]
4. (b)(ii)Use Faraday's law and energy conservation to explain why the amplitude of the oscillations of the magnet reduces after time t = 6.0s.[3]

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