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Unformatted text preview: ltage source at steady state.
In ideal capacitor, the charge developed in each plate (charge stored) is proportional to the voltage across it. Q CV where C , the proportionality constant is called the capacitance. Its unit is farad (F). One farad is equivalent to coulomb per volt. One farad is a large value and practical capacitors have values only a few pico farad (10‐12) to a few micro farad (10‐6). 60 EE1002 Introduction to Circuits and Systems Capacitor current in terms of voltage Current is the rate of flow of charge. When charge is accumulating on the capacitor plates, the rate of this accumulation can be obtained as: dq (t ) d
dv(t ) Cv(t ) C
dv(t ) is i‐v relation for a capacitor. i (t ) C
i (t ) From above equation, a capacitor current is present only when charge is building up. At steady state, when the voltage is stable, the capacitor current will be zero. Hence, capacitors in DC circuits behave as open circuited in steady state. Capacitor voltage in terms of current Rearranging the above equation we get the rate of change of voltage in terms of the capacitor current. dv(t ) 1 i (t )
v(t ) v(t0 ) i (t )dt C t0
t v(t ) q0 1 i (t )dt
C C t
0 The i...
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This document was uploaded on 01/20/2014.
- Winter '14