Magnets and magnetic fields — final check

1. describe / state

(a) Two magnets are brought together with an N pole facing an N pole. Describe what happens, using the word attraction or repulsion. (b) A plotting compass is carried 30 cm away from a bar magnet. There its needle still turns a little each time the magnet is turned round. State whether the compass is in the magnet’s magnetic field, and give the reason, using what is meant by a magnetic field. (c) A compass is placed near a magnet, and the north-seeking end of its needle points east. State the direction of the magnetic field at that point, and give the reason.

(a) N facing N

(b) In the field or not?

(c) Direction at the compass

2. describe / state

(a) Describe how to plot the magnetic field lines round a bar magnet with a plotting compass. (b) Sketch, on paper, the pattern of the field lines round a bar magnet, with arrows to show their direction. Draw at least four lines. (c) State one thing iron filings show about the field and one thing they cannot show.

(a) Plotting with a compass

(b) Your sketch: what it shows

(c) What filings show

3. explain / state / identify

Supplement. (a) Two identical bar magnets lie on a line with their N poles facing, 10.0 cm apart. Explain, in terms of their magnetic fields, why they repel, and state where the neutral point is. (b) On a drawing of one magnet’s field, the lines are 1 mm apart at point A and 6 mm apart at point B. Identify the point with the stronger field.

(a) Why they repel; the neutral point

(b) The stronger field

4. state / describe

(a) A pupil sorts four objects into magnetic and non-magnetic materials: a silver spoon, an iron nail, a zinc sheet and a cobalt disc. State the difference between the two kinds of material, and identify which of the four objects are made of magnetic materials. (b) Two bars look the same. One is a magnet and the other is unmagnetised iron. You have a labelled bar magnet. Describe how you could tell them apart, using the words attraction, repulsion, magnetised and unmagnetised.

(a) Magnetic and non-magnetic

(b) Telling the bars apart

5. state / describe / identify

Two rods of the same size, A and B, each hang with their top end touching the N pole of identical magnets. Rod A holds 9 paper clips and rod B holds 6. When the magnets are removed, rod A drops all its clips and rod B keeps 5. (a) State the pole induced at the top of each rod while it touches the magnet. (b) Describe how the clips are held to the rods. (c) Identify which rod is steel, and state two differences between the properties of soft iron and steel.

(a) The pole at the top

(b) How the clips are held

(c) Which rod is steel; two differences

6. describe / explain / state

(a) Describe one use of a permanent magnet and one use of an electromagnet. (b) For each use, explain why that kind of magnet is chosen. (c) State what a simple electromagnet is made of.

(a) Two uses

(b) Why each kind

(c) A simple electromagnet