Explain electrical energy and derive its formula. Obtain Joule.s law o

1.	Explain electrical energy and derive its formula. Obtain Joule.s law of heating.
Answer» Solution :A metallic conductor (or a resistance WIRE) OFFERS resistance to the flow of current, so work must be done by the current-source for a continuous flow of electric current through a conductor. Consider a current I flowing through a resistor (or conductor) of resistance R. Let V be the potential difference across the resistor (see figure). Let t be the time-INTERVAL during which a charge Q flows through the resistor (conductor). The work done by the current source in moving charge Q through a potential difference V is vg. Therefore, the current source must supply energy to the circuit equal to VQ in time t. Thus, energy spent by the source or thework done by the source, `W = VQ` `= V ("It") ( :. I = Q/t)` `=(IR) ("It")` (By the Ohm.s law V =IR) `:. W = I^2Rt... ....(12.15)` This electrical energy gets dissipated as heat in the resistor. Thus for a steady current I, the amount of heat H generated (produced) in time- interval t is `H = I^2 Rt`.......(12.16) This is known as the JOULE.s law of heating. The SI unit of electrical energy and heat energy is the joule (J). Its other units are watt-second (Ws) and kilowatt-hour (kWh) or unit (commercialunit for electrical energy).

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