1. USING ELECTRICITY – Class 7 HEATING EFFECTS OF ELECTRICITY Done by Mrs. Aparna.S

2. HEATING EFFECT OF ELECTRICITY Concept, Application and Uses

3. HEATING EFFECT OF ELECTRICITY  When electricity is passed through a conductor (wire), a part of it is converted into heat energy and heats up the conductor (wire).  This kind of heating is called Ohmic or Joule heating  The heat produced depends on: The current (number of cells) The material of the wire The time for which the current is passed

4.  The heating effect of current has many practical applications.  Eg. Electric bulbs, toasters, iron box, room heater, induction cookers, electric kettle, geyser, hot plates, immersion heater, ovens, hairdryers, electric water boilers and many more… HEATING EFFECT OF ELECTRICITY

6.  Has a long, flat strip of nichrome wire (heating element / tube)  Nichrome has a very high melting point and does not melt even when it is white hot  So, it can be heated to a high temperature by passing an electric current HEATING EFFECT OF ELECTRICITY – Iron box

7.  Another important application of this heating effect of electricity is in a ‘fuse’  Electrical appliances work when an electric current passes through them.  Every electrical circuit is allowed to carry a certain load of current. HEATING EFFECT OF ELECTRICITY - FUSE

8.  Sometimes, when a large amount of electric current is drawn into an appliance, it causes the wires to get overheated, and the appliance gets damaged or the insulation may even catch fire!  This may happen when: There is a short circuit (positive and negative wires coming directly into contact accidentally) Any other fault in the circuit like overloading of current HEATING EFFECT OF ELECTRICITY - FUSE

9.  To prevent this, a safety device called a ‘fuse’ is included in every circuit  A fuse is a safety device used in an electrical circuit to prevent a large amount of current flowing through a circuit.  It consists of an alloy of low melting point fitted into a carrier made of porcelain or glass.  Fuses are commonly found inside electric plugs HEATING EFFECT OF ELECTRICITY - FUSE

10.  Types : Cartridge fuses and Ceramic fuses HEATING EFFECT OF ELECTRICITY - FUSE SYMBOL FOR A FUSE:

11.  If a fuse blows, switch off all appliances in the circuit, and pull out all their plugs.  Get an electrician to locate and repair the fault and then fit a new fuse (with a proper fuse wire and not any kind of wire) HEATING EFFECT OF ELECTRICITY - FUSE

12.  These days, fuses are increasingly being replaced by miniature circuit breakers (MCB)  A miniature circuit breakers (MCB) is an automatically operated electric switch that protects an electric circuit during a fault  Advantage over a fuse: They can be manually or automatically reset to restore normal operation; Fuses need to be replaced after single operation HEATING EFFECT OF ELECTRICITY - MCB