Electric Current and its Effects Class 7 Science Notes - Chapter 14

Representation of electric components is very easy with the help of symbols. Drawing a circuit diagram is done conveniently with the help of these. Heating effect of the current is defined as, the heating of wire due to the flow of electric current through it. When the electric current is flowing through the wire, it acts as a magnet. It has several applications. Some wires are made of unique materials. Such wires melt rapidly and when a large electric current is passed through them they break. One major example of such material is an electric fuse. Electric fuses prevent fire as well as damage to any electric appliance. An electromagnet is defined as an insulated wire coil carrying current is wrapped around an iron piece. Some of the applications of electromagnets-

  • Transformers – It is a static electrical machine to transfer electrical energy between two or more than two circuits.
  • Electromagnetic Lock – It is also called maglock. It is a device comprising of an electromagnet and an armature plate.

Few Important Questions

  1. List the effects of electric current.
  2. Can we use an electromagnet to separate plastic from garbage heap?
  3. Draw symbols for the following-
    1. (a)Cell (b) Connecting wire (c) Switch ON (d) Bulb (e) Battery (f) Switch OFF
  1. Fill in the blanks –
    1. When two or more cells are combined, it is called _________.
    2. Heating effect safety device on electric current is called ________.
    3. For a cell symbol of the longer line represents its ___________ terminal
  1. Answer true or false –
    1. Electromagnets attract iron pieces.
    2. In a two cell battery, the negative terminal of both the cells is connected to each other.
    3. An electric bell does not have an electromagnet.

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