Question

An electric iron of resistance 20 Ω draws a current of 5 A. The heat developed in the iron in 30 seconds is :

Write Joule's law of heating. How is this effect useful in electric circuits where fuse is used as a safety device ?

Explain in brief the function of an electric fuse in a domestic circuit. An electric heater of current rating 3 kW; 220 V is to be operated in an electric circuit of rating 5 A. What is likely to happen when the heater is switched 'ON' ? Justify your answer with necessary calculation.

Study the following statements : (a) A fuse in a circuit prevents damage to the circuit due to overloading. (b) Total resistance in a circuit increases due to overloading. (c) During short circuiting the current in the circuit abruptly increases. (d) In order that each appliance has same current, they are connected in parallel to each other. The correct statements are

When electric current flows in a purely resistive circuit electrical energy gets fully converted into heat energy. The amount of heat produced (H) in the circuit is found to be directly proportional to (i) the square of current (I²) (ii) the resistance (R) of the conductor and (iii) the time (t) for which current flows. In other words H = I²Rt. Electrical devices such as an electric fuse, electric heater, electric iron etc. are all based on this effect called heating effect of electric current.