Preliminary Questions:Suppose you have an RC circuit with R = 50, C = 0.2F, hooked up to a battery with V = 5V. We are going to charge the capacitor.

1. Using the equations above what is the time constant ?(s)

1. When t = what is the value of the voltage? (V)

1. What percentage of the battery voltage is the voltage across the capacitor at this time?

1. When t = 2what is the value of the voltage? (V)

1. What percentage of the battery voltage is the voltage across the capacitor at this time?

1. By what percentage of the battery voltage did the voltage across the capacitor change from t = to t = 2?

1. Is the following statement true: During charging, the capacitor gains the largest fraction of its final voltage during the time t = to t = 2.

Simulation

To begin make sure your capacitor is discharged. That is the potential difference or voltage across the capacitor is zero. You can use the voltmeter to check that it is zero. If it is not zero we can discharge the capacitor by closing switch 2 and opening switch 1. Once the voltage is zero leave switch 1 open and open switch 2.

Since this is a simulation, it also gives you the option to right click on the capacitor and choose discharge or charge capacitor. If you choose to do this for your setup make sure both switches are open so the capacitor will remain in the charged/discharged state until you are ready.

You are going to time the charging of the capacitor, i.e. the time and it takes for the capacitor to reach a specific value Vc. This can be done with your own stopwatch or the stopwatch in the simulation (it is much easier to use your smartphone as the stop watch). When your ready, start you first measurement Vc = 0.5V and repeat (or it might be more convenient to use the lap function on your stopwatch).

Make a copy of the the table below to collect your data (no need to turn it in). The voltage increases faster at the beginning.

Vc	0.5V	1.0V	1.5V	2.0V	2.5V	3.0V	3.5V	4.0V	4.5V	5.0V
Time

Plot Vc as a function of time.

1. Looking at the plot, at about what time did the voltage reach 63% of its total voltage? (s)

1. Assume you do not know the value of the capacitor C, calculate Cfrom the knowledge of

Rand time constant found in question 1. (F)

1. What is the percent error between the calculated values and the exact value of C?

Plot in a semi-log format.

If you solve V _C(t)=V (1e^t/ ) for e^t/and take the natural log of each side, then you can plot y=ln(1V _C/V) vs and x=t. Draw a single line of best fit through your data.

1. Write your result as y =m x,what is the value of m? (1/s)

1. Using your plot and the result from question 4, what value of do you find? (s)

1. Again assuming we do not know the capacitance solve for C using your fitted value of and the known value of R. (F)

1. What is the percent error between the calculated value and the exact value of C?

Discharging a Capacitor

Preliminary Questions:Suppose again you have an RC circuit with R = 50, C = 0.2F, hooked up to a battery with V = 5V. This time we will discharge the capacitor.

1. Is the time constant different when we discharge a capacitor?

1. When t = what is the value of the voltage? (V)

1. What percentage of the battery voltage is the voltage across the capacitor at this time?

1. When t = 2what is the value of the voltage? (V)

1. What percentage of the battery voltage is the voltage across the capacitor at this time?20. By what percentage of the battery voltage did the voltage across the capacitor change from t = to t = 2?

1. Is the following statement true: During discharging the capacitor loses the largest fraction of its initial voltage during the time t = to t = 2.

Repeat the set of measurements taken above but now you discharge the capacitor rather then charge it. The capacitor needs to be fully charged before you start. If you have not changed anything your capacitor should be charged from the previous step at 5V. If not you can open both switches and right click on the capacitor and select the charge option.

When you are ready, leaving switch 1 open, close switch 2 and begin timing the discharge of the capacitor as it discharges from 5V to 0V. Make a copy of the the table below to collect your data (no need to turn it in). The voltage increases faster at the beginning.

Vc	4.5V	4.0V	3.5V	3.0V	2.5V	2.0V	1.5V	1.0V	0.5V	0.0V
Time

Plot Vc as a function of time.

22. Looking at the plot at about what time did the voltage reach 36.8% of its total voltage?

(s)

23. Assume you do not know the value of the resistor R,calculate R from the knowledge of

C and the time constant found in question 1. ()

1. What is the percent error between the calculated values and the exact value of R? Plot in a semi-log format.

If you solve V _C(t)=V e^t/for e^t/and take the natural log of each side, then you can plot y=ln(V _C/V) vs and x=t. Draw a single line of best fit through your data.

1. Write your result as y =m x,what is the value of m? (1/s)

1. Using your plot and the result from question 11, what value of do you find? (s)

1. Again assuming we do not know resistance solve for R using your fitted value of and the known value of C. ()

1. What is the percent error between the calculated value and the exact value of R?

Summary and conclusions (describe what did you learn from animation and basic principles of this lab)