RI Y6 Remedial EMI Assignment

Raffles Institution Year 5-6 Physics Department 1 2025 Year 6 H2 Physics Remedial Chapter 17: Electromagnetic Induction 1 Fig. 1.1 below shows a simple electric generator that can convert mechanical energy into electrical energy. A metal rod CD of mass M and is able to slide downwards while maintaining contact with two long smooth vertical metal rails PQ and ST. The rods are connected at the bottom by a resistor R, and the whole device is in a uniform magnetic field B perpendicular to the page. When the rod is released from rest, it falls downwards and as a result, an electric current I flows around the circuit CDTQ. The rod speeds up initially before reaching a constant downward speed. Fig. 1.1 (a) Draw on the diagrams below clearly labelled arrows to represent the vertical forces acting on the rod CD in the two cases. (i) just as it was released (ii) falling with constant speed [2] P S Q T

Raffles Institution Year 5-6 Physics Department 2 (b) Fig. 1.2 below shows the rod descending a distance ∆ y in a time ∆t at constant speed vT. Fig. 1.2 (i) Write an expression for the change of magnetic flux ∆φ as the rod CD falls through distance ∆y. [1] (ii) Hence show that the induced e.m.f. E is given by E = BLvT. [1] (iii) Using (a)(ii) and (b)(ii), show that the constant speed vT is given by T MgRv BL= 22 Explain your working clearly. [3] (c) State a disadvantage of this type of generator compared to a conventional rotating generator. [1] (HCI/Prelims/2014/III) 2 A small coil is positioned so that its axis lies along the axis of a large bar magnet as shown in Fig. 2.1. Fig. 2.1 ∆y P Q S T L

Raffles Institution Year 5-6 Physics Department 3 The coil has a cross-sectional area of 0.40 cm2 and contains 150 turns of wire. The average magnetic flux density B through the coil varies with the distance x between the face of the magnet and the plane of the coil, as shown in Fig. 2.2. Fig. 2.2 (a) The coil is 5.0 cm from the face of the magnet. With reference to Fig. 14.2, show that the magnetic flux linkage of the coil is 3.0 x 10-4 Wb. [2] (b) The coil is moved along the axis of the magnet so that the distance x changes from x = 5.0 cm to x = 15.0 cm in a time of 0.30 s. Calculate (i) the magnitude of the change in flux linkage of the coil, [2] (ii) the average e.m.f induced in the coil. [2] (c) State and explain the variation, if any, of the speed of the coil so that the induced e.m.f. remains constant during the movement in part (b). [2] (d) The magnet in Fig. 14.1 is now replaced with a solenoid connected to an alternating voltage, with the axis of the solenoid aligned