Power = Voltage × current current = powervoltage = 24/12 = 2A Time = 2 min = 2 × 60 seconds = 120 seconds Heat energy = Voltage(V) ×current (I) ×time (t) = 12 × 2 × 120 = 2880 Joules Regards
The wattage of a bulb is 24 W when it is connected to a 12 V battery. Calculate its effective wattage if it operates on a 6 V battery.
(a) Derive the expression for the heat produced due to a current I flowing for a time interval t through a resistor R having a potential difference V across its ends. With which name is this relation known? (b) How much heat will an instrument of 12 W produce in one minute if it is connected to a battery of 12 V? (c) The current passing through a room heater has been halved. What will happen to the heat produced by it? (d) What is meant by the heating effect of current? Give two applications of the heating effect of current. (e) Name the material which is used for making the filaments of an electric bulb.