Справочник Пользователя для PASCO Specialty & Mfg. AC/DC Electronics Laboratory EM-8656
23
012-05892A
AC/DC Electronics Laboratory
®
3 VOLTS MAX
C
E
–
+
Battery
C
W
–
Battery
Experiment 8: Capacitors in Circuits
EQUIPMENT NEEDED:
– AC/DC Electronics Lab Board: Capacitors, Resistors, Wire Leads
– D-cell Battery
– Stopwatch or timer with 0.1 sec resolution.
– Vacuum Tube Voltmeter (VTVM) or Electrometer (ES-9054B) or Digital Multimeter
– D-cell Battery
– Stopwatch or timer with 0.1 sec resolution.
– Vacuum Tube Voltmeter (VTVM) or Electrometer (ES-9054B) or Digital Multimeter
(DMM) that has an input impedance of 10 M
Ω
or greater.
Purpose
The purpose of this lab will be to determine how capacitors behave in R-C circuits. The manner in
which capacitors combine will also be studied.
which capacitors combine will also be studied.
Procedure
➀
Connect the circuit shown in Figure 8.1, using a 100 k
Ω
resistor and a 100
µ
F capacitor. Connect
the circuit as shown in Figure 8.1. Connect the VTVM so the black “ground” lead is on the side of
the capacitor that connects to the negative terminal of the battery and set it so that it reads to a
maximum of 1.5 V DC.
the capacitor that connects to the negative terminal of the battery and set it so that it reads to a
maximum of 1.5 V DC.
➁
Start with no voltage on the capacitor
and the switch off. If there is remaining
voltage on the capacitor, use a piece of
wire to “short” the two leads together,
draining any remaining charge. (Touch
the ends of the wire to points B and C as
shown in Figure 8.1 to discharge the
capacitor.)
and the switch off. If there is remaining
voltage on the capacitor, use a piece of
wire to “short” the two leads together,
draining any remaining charge. (Touch
the ends of the wire to points B and C as
shown in Figure 8.1 to discharge the
capacitor.)
➂
Now close the switch by pushing and
holding the button down. Observe the
voltage readings on the VTVM, the
voltage across the capacitor. How would
you describe the manner in which the
voltage changes?
holding the button down. Observe the
voltage readings on the VTVM, the
voltage across the capacitor. How would
you describe the manner in which the
voltage changes?
➃
If you now open the switch by releasing the button, the capacitor should remain at its present
voltage with a very slow drop over time. This indicates that the charge you placed on the capacitor has
no way to move back to neutralize the excess charges on the two plates.
voltage with a very slow drop over time. This indicates that the charge you placed on the capacitor has
no way to move back to neutralize the excess charges on the two plates.
➄
Connect a wire between points A and C in the circuit, allowing the charge to drain back through
the resistor. Observe the voltage readings on the VTVM as the charge flows back. How would
you describe the manner in which the voltage falls? (It would be reasonable to sketch a graph
showing the manner in which the voltage rose over time as well as the manner in which it fell over time.)
the resistor. Observe the voltage readings on the VTVM as the charge flows back. How would
you describe the manner in which the voltage falls? (It would be reasonable to sketch a graph
showing the manner in which the voltage rose over time as well as the manner in which it fell over time.)
➅
Repeat steps 3-5 until you have a good feeling for the process of charging and discharging of a
capacitor through a resistance.
capacitor through a resistance.
➆
Now repeat steps 3-5, this time recording the time taken to move from 0.0 volts to 0.95 volts while
charging, t
charging, t
C
, and the time taken to move from 1.5 volts to 0.55 volts while discharging, t
D
. Record
your times along with the resistance and capacitance values in Table 8.1 at the top of the back page.
-
Switch
Figure 8.1
+
Cap
Res
C
B
A
V