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Class 10 Science — Magnetic effects of electric current

Read a field-line diagram for direction and strength, pick the right-hand thumb rule or Fleming's left-hand rule for the job, and explain what the earth wire and the fuse are doing in a house circuit.

Name: ________________________

  1. 1.A house has two separate circuits, one rated 15 A and one rated 5 A. Which appliances go on which?

    • a) Lighting on both, with the 15 A circuit kept in reserve
    • b) Everything on the 15 A circuit, with the 5 A one kept spare
    • c) Geysers and air coolers on the 15 A circuit; bulbs and fans on the 5 A one
    • d) Bulbs and fans on the 15 A circuit; geysers and air coolers on the 5 A one

  2. 2.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 joins the body to the neutral wire
    • c) It raises the potential of the body above the earth's
    • d) It stops the refrigerator from drawing too much current

  3. 3.Match each wire of the domestic supply to the colour of its insulation.

    • The live wire
    • The neutral wire
    • The earth wire
    • Black
    • Red
    • Green

  4. 4.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.

  5. 5.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

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

    Write the number of the part.

    12

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

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

  8. 8.Why can two magnetic field lines not cross?

    • a) A compass at the crossing would have to point two ways at once
    • b) The lines are drawn too thick to overlap
    • c) The two fields would cancel out at the crossing
    • d) Field lines are closed curves, and closed curves cannot meet

Answer key — Class 10 Science — Magnetic effects of electric current

  1. 1. c) Geysers and air coolers on the 15 A circuit; bulbs and fans on the 5 A one
  2. 2. a) It gives leaking current a low-resistance path, so the body stays at the earth's potential
  3. 3. The live wire → Red; The neutral wire → Black; The earth wire → Green
  4. 4. 12
  5. 5. d) The field is the same at points inside it — it is uniform
  6. 6. 1 — Close to the end of the magnet, where the lines are crowded
  7. 7. a) The magnetic field
  8. 8. a) A compass at the crossing would have to point two ways at once