A computer hard disk contains a layer of a magnetic material. [Figure 7.1 (not to scale) shows part of a hard disk with a coil positioned above a thin layer of magnetic material. The magnetic material is divided into regions with N-poles and S-poles (S N N S S N S N N S). Magnetic field lines are shown near the boundaries between regions. Region 1 is labelled (S N) and Region 2 is labelled (S N).]

1. (a)Describe how a magnet is used to find out if a sample of material is magnetic or non-magnetic.[1]
2. (b)(i)Data is stored on the disk as a series of N-poles and S-poles. Fig. 7.1 shows part of the hard disk. The thin layer of magnetic material contains small regions. Each region has an N-pole and an S-pole. Some magnetic field lines are shown on Fig. 7.1. Region 2 causes a magnetic force on region 1. State the direction of the magnetic force on region 1 and explain why it acts.[2]
3. (b)(ii)On Fig. 7.1, draw arrows on the field lines to show the direction of the magnetic field near the boundary between region 1 and region 2.[1]
4. (b)(iii)1.The coil shown in Fig. 7.1 is fixed in position. The layer of magnetic material passes quickly under the coil. A voltage is induced in the coil as some of the boundaries between the regions pass under the coil. Explain why a voltage is induced in the coil.[1]
5. (b)(iii)2.Suggest why the coil must be close to the layer.[1]

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