Transcript Unit 3 Day 11 – RC Circuits

Unit 3 Day 11: RC Circuits
• RC Circuit Introduction
• RC Circuit Analysis
• RC Time constant
• Charging and discharging
of an RC Circuit
RC Circuits
• Circuits that contain both resistance and
capacitance are called RC Circuits
• RC Circuits are used in timing circuits, camera
flashes, pacemakers
• RC Circuit analysis is not just interested in
steady state voltage and currents but rather how
the circuit behaves over time
RC Transient Analysis
I
VC
Q (t )
V (t )  I (t )  R 
C
RC Circuit Transient Analysis

V   1  e
 t RC
C
I  I 0e
 t RC
where I 0 
and let   RC

R
•  is a time constant
• The voltage across the capacitor
reaches 98% of the battery
EMF in 4 
• The transient response of the circuit is
over in approximately 4 - 5
Discharging RC Circuit
• Suppose a capacitor is charged to a voltage V0, and then
connected across a resistor as shown below.
I  I 0e
 t RC
and
VC  V0 e
 t RC