Physics 2B Lab
Series RC Circuit Time Constant
Objective:
To determine the time constant of an RC circuit
Theory:
A capacitor, C, creates an open or disconnected circuit.
If the series circuit with a capacitor and
resistor, R, is powered by direct current (DC) power supply or battery, charges will accumulate
on the capacitor plates until the two have equal voltages. If the switch is closed at t=0, we find
that the charge, q(t), on the capacitor at a later time, t, increases as follows
q(t) =Q
0
(1e
t/RC
)
1.
where e is equal to 2.718
The product RC is called the time constant,
τ
., and represents the time it takes to increase the
charge on the capacitor from zero to 63.2%.
If the battery is removed from the circuit and the
circuit reconnected the capacitor would also lose 63.2% of its charge in time t, or would decrease
to down to 36.8% of Q
0
.
[ Refer to section 18.5 , on page 475, in course textbook]
Materials Needed:
1.
One 10 k
Ω
Resistor
2.
One .01
υ
F Capacitor
3.
One Oscilloscope
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 Spring '09
 sydney.sukuta
 Physics, Power, RC circuit, RC time constant, series rc circuit, Circuit Time Constant, Lab Series RC

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