^ This is our physics project --- ^ This is our results ------------- I need you
ID: 2240800 • Letter: #
Question
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This is our physics project
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This is our results
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I need you to answers this question
1- What is the Purpose ( 4 objective ) ?
2- What is the Procedure (simple past ) ?
3 - What is the effect on charging and discharging times if the capacitance is increased?
4- What mathematical relationship exists between your times and the capacitance?
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 (DMM) that has an input impedance of 10 Mohm 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. Procedure Connect the circuit shown in Figure 8. 1. using a 100 kohm resistor and a 100 muF 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 15 V DC. 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. ) 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? 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 die capacitor has no way to move back to neutralize the excess charges on die two plates. 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 manna in which it fell over time. ) Repeat steps 3-5 until you have a good feeling for the process of charging and discharging of a capacitor through a resistance. Now repeat steps 3-5, this time recording the time taken to move from 0. 0 volts to 0. 95 volts while charging, tc, and the time taken to mow from 1. 5 wits to 0. 55 volts while discharging. tD. Record your times dong with the resistance and capacitance values in Table 8. 1 at the top of die back page. Replace the 100 muF capacitor with a 330 muF capacitor. Repeat step 7, recording the charging and discharging times in Table 8. 1. If a third value is available, include it in the data table, too. Return to the original 100 muF capacitor, but put a 220 kohm resistor in the circuit. Repeat step 7, recording your data in Table 8. 1. If a third resistor is provided, use it in the circuit, recording the data. NOTE: What is the effect on charging and discharging tunes if the capacitance is increased? What mathematical relationship exists between your times and the capacitance? What is the effect on charging and discharging times if the resistance of the circuit is increased? What mathematical relationship exists between your times and the resistance? Return to the original 100 kohm resistor, but use the 100 muF capacitor in series with the 330 muF capacitor. Repeat step 7. recording your results in Table 8. 2. Now repeat step 7. but with the 100 muF and the 330 muF capacitors in parallel.Explanation / Answer
(a) purpose is :
1) effect on capacitor due to resisitance.
2) charge holding capacity of capacitor.
3) charging& discharging rates of capacitor.
4)Effect of V & I on capacitor.
(b) procedure is just about connecting resistance & capacitor in series and then changing value of
capacitor:
1) connect known resistance with battery of 220V in series.
2) connect capacitor in series with resistor & voltmeter parallel to capacitor.
3)switch on until voltmeter shows no change in deflection with time.
4)disconnect battery and connect capacitor parallel to resistance for discharging.
5) repeat steps with different capacitors & resistors.
(c) the charging time AND the discharging time both depend on the size of the capacitor and the series resistance.If you adjust the series resistance, you can make the capacitor charge faster than it discharges, charge & discharge at the same rate, or discharge faster than it charges.
but if resistance is kept constant it takes less time discharge & longer time to charge.
(d) Vo=V(1-e^-(t/T)) charge
or Vo=Ve^-(t/T) discharge
Where T=CR
V=supply
Vo = Voltage on the capacitor after time, t
resistance acts similar to capacitance.
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