Year 11 Science — Magnetic effects of electric current

1.Field lines round a bar magnet are drawn below. Tap the part of the picture where the field is strongest.

2.Outside a bar magnet, which way do the field lines run?

• a) Out of the south pole and into the north pole
• b) From the middle of the magnet outwards at both ends
• c) Into both poles from the surrounding space
• d) Out of the north pole and into the south pole

3.In Fleming's left-hand rule, what does the first finger point along?

• a) The force on the conductor
• b) The motion of the electrons
• c) The magnetic field
• d) The current

4.Why is the metallic body of a refrigerator connected to the earth wire?

• a) It gives leaking current a low-resistance path, so the body stays at the earth's potential
• b) It raises the potential of the body above the earth's
• c) It stops the refrigerator from drawing too much current
• d) It joins the body to the neutral wire

5.What is short-circuiting?

• a) A drop in the supply voltage
• b) Too many appliances plugged into one socket
• c) The earth wire breaking away from its plate
• d) The live wire and the neutral wire coming into direct contact

6.What do the parallel straight field lines inside a current-carrying solenoid tell you?

• a) The solenoid has no poles
• b) There is no field inside the solenoid
• c) The field inside is stronger at the ends than in the middle
• d) The field is the same at points inside it — it is uniform

7.A piece of soft iron is put inside a solenoid and the current is switched on. What has been made?

• a) An electromagnet
• b) A fuse
• c) A rheostat
• d) An electric generator

8.A single circular turn of wire makes a field of a certain strength at the centre of the loop. A coil of 12 such turns carries the same current. How many times that strength is the field at the centre now? Answer with a number.