A vertical solenoid (long coil) with an iron core is held in a wooden clamp above a laboratory bench. The solenoid is connected in series with a battery, a switch S, an ammeter and a variable resistor. There is a voltmeter in parallel with the solenoid. Fig. 9.1 represents this apparatus. [Figure 9.1] A student closes switch S and a current in the circuit produces a reading on the ammeter.

1. (a)State what is meant by current. ...............................................................................................................................................[1][1]
2. (b)The battery consists of five 1.5V cells in series. The reading on the ammeter is 4.0A.
3. (b)(i)State the size of the electromotive force (e.m.f.) of the battery. ...............................................................................................................................................[1][1]
4. (b)(ii)Calculate the total resistance of the series circuit. resistance = ..............................................................[2][2]
5. (b)(iii)The reading on the voltmeter is 6.5 V. Calculate the power dissipated in the solenoid. power = ....................................................................[2][2]
6. (b)(iv)The solenoid is made of copper and the student notices that, as time passes, the solenoid becomes extremely warm. State and explain the effect of this temperature increase on the ammeter reading. ............................................................................................................................................... ...............................................................................................................................................[2][2]
7. (c)(i)The current in the solenoid magnetises the iron core so that the lower end of the core is an N-pole. On Fig. 9.1, draw the pattern and indicate the direction of the magnetic field in the region surrounding the iron core. [3][3]
8. (c)(ii)The student holds an iron cylinder against the bottom surface of the iron core in the solenoid. When he releases the iron cylinder, it stays in contact with the iron core.
9. (c)(ii)1.Explain why the iron cylinder does not fall. ............................................................................................................................................... ............................................................................................................................................... ...............................................................................................................................................[3][3]
10. (c)(ii)2.The switch S is opened. State and explain whether the iron cylinder remains in contact with the iron core. ............................................................................................................................................... ...............................................................................................................................................[1][1]

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