By evaluating ∫i2R dt, show that when a capacitor is charged by connecting it to a battery through a resistor, the energy dissipated as heat equals the energy stored in the capacitor.

Concepts/Formulas Used:


Energy dissipated by a resistor :


A resistor of resistance R with current I through it, dissipates energy U given by:



in time Δt.


Its power is given by:



Current when capacitor is charging:


A capacitor of capacitance C is being charged by a battery of emf V through a resistance R is series , the current through the circuit is given by:



Where



Suppose a capacitor of capacitance C is being charged by a battery of emf V through a resistance R.


Now, the power of the resistor is given by:





Substituting ,






Substitute



This is the same as the energy stored in the capacitor when it is fully charged! (Note that when the capacitor is fully charged, the potential difference across it is V.)


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