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www.GOALias.blogspot.comFig. 14.7 An electric circuitFig. 14.8 Circuit diagram of electric circuitshown in Fig. 14.7• Notice that the key or switch canbe placed anywhere in the circuit.• When the switch is in the ‘ON’position, the circuit from thepositive terminal of the battery tothe negative terminal is complete.The circuit is then said to be closedand the current flows throughoutthe circuit instantly.• When the switch is in the ‘OFF’position, the circuit is incomplete.It is said to be open. No currentflows through any part of thecircuit.In the bulb there is a thin wire, calledthe filament, which glows when anFig. 14.9 Another circuit diagramelectric current passes through it. Whenthe bulb gets fused, its filament isbroken.If the filament of the bulb is broken,would the circuit be complete? Wouldthe bulb still glow?You might have noticed that aglowing electric bulb become warm. Doyou know why?14.2 HEATINGEFFECTOF ELECTRICCURRENTActivity 14.2CAUTIONNever touch a lighted electric bulbconnected to the mains. It may be veryhot and your hand may get burntbadly. Do not experiment with theelectric supply from the mains or agenerator or an inverter. You may getan electric shock, which may bedangerous. Use only electric cells forall the activities suggested here.Take an electric cell, a bulb, a switchand connecting wires. Make an electriccircuit as shown in Fig.14.9. Thisactivity has to be done using only onecell. Keep the switch in the ‘OFF’163ELECTRICCURRENTAND ITS EFFECTS163