physics lab report

 

this is lab report
Lab Report The lab report must consist of the following
A) Cover Page,
B) Results and Analysis,
C) Discussion,
D) Conclusions,
and E) Post-Lab Question (s) and/or At-Home Activity.

Your lab report must reflect strictly your individual efforts.

A) Cover Page with Objective(s) Your Name Course Number and Section Number Instructor’s Name Date Experiment was performed Title of Experiment Objective(s): A few sentences describing the primary goal(s) of the experiment.
B) Results and Analysis Consists of the completed Experimental Handout (include all pages from Blackboard handout) Be sure to include all measurements taken and analysis performed.
C) Discussion
1. Discuss and explain your results by comparing them with the theory.
2. Suggest any procedural improvements and explain how they might enhance your results.
D) Conclusions Your conclusions should summarize (in a few sentences) what can be deduced from your measurements (refer to the physical principles involved) and explain how your results meet the objectives of the experiment. E) Post-Lab Question (s) and/or At-Home Activity (10 pts. )

Last Name ________________________  First Name _____________________   Lab Section _______

 

Instructor _______________________________________      Date  ____________                                        

 

 

RC Circuit

 

Background:

 

For background on RC circuits see textbook, class notes, homework problems, and/or web sources.  Have available for reference the equations that pertain to both charging and discharging of the RC circuit, i.e. Q(t), V(t), and I(t) for both processes.

 

Here is the link to the PhET simulation that you are going to use for this experiment:

 

PhET Circuit Construction Kit (DC)

 

 

Got to the RLC tab.  Note:   Values for the circuit elements may be set (within certain ranges).

 

 

 

 

 

 

 

 

Part A            Charging of a RC Circuit

 

• Construct a RC circuit (series) with a capacitor, a resistor, a battery, two switches, and appropriate meters that will enable you to make measurements of the parameters for charging up the capacitor. The placement of the switches allows you to measure both charging and discharging of the RC circuit.   See diagram below:

 

 

 

 

• Choose a combination of R and C that will give you a time constant of 20 seconds.

 

• Set the battery voltage to 100 volts.

 

Capacitor voltage versus time

 

• Set up a table to record time (in multiples of the time constant) and voltage (across the capacitor).

 

Warning:  Make sure that the capacitor is discharged before making measurements.

 

• As close to simultaneously as you can, close switch #1 (closest to the battery) and then turn on the stopwatch. When the time reaches the value that you want to record just open switch #1 and record both the time (that you had chosen) and the voltage (there is no need to turn off the stopwatch simultaneously).  Use time intervals of the time constant (zero to 5).

 

• Graph (G1) the results for step 5) (i.e. capacitor voltage versus time).

 

Resistor voltage versus time

 

• Set up a table to record time (in multiples of the time constant) and voltage (across the resistor).

 

• Repeat step 5) but put the voltmeter across the resistor for these measurements.

 

• Graph (G2) the results for step 8) (i.e. resistor voltage versus time).

 

Current versus time

 

• Set up a table to record time (in multiples of the time constant) and current (through the resistor and capacitor).

 

• Using the same setup as in step 8) repeat step 5) but instead of recording the voltage, when the time get to the desired value, record the current reading on the ammeter.

 

• Graph (G3) the results for step 11) (i.e. current versus time).

 

 

 

 

 

Part B                  Discharging of a RC Circuit

 

In this part of the experiment you will use the same circuit as in Part A but now you will make measurements of the discharging of the RC circuit.

 

 

Capacitor voltage versus time

 

 

• Change the voltmeter so that it is reading the voltage across the capacitor.

 

• Set up a table to record time (in multiples of the time constant) and voltage (across the capacitor).

 

• Charge up the capacitor by closing switch #1 for a time equal to 10 time constants. Then open switch #1.  Record the voltage across the capacitor.  (Warning:  Don’t discharge it!)  Move the stopwatch near switch #2 to the measurements.

 

• As close to simultaneously as you can, close switch #2 (farthest from the battery) and then turn on the stopwatch. When the time reaches the value that you want to record just open switch #2 and record both the time (that you had chosen) and the voltage (there is no need to turn off the stopwatch simultaneously).  Use time intervals of the time constant (zero to 5).

 

• Graph (G4) the results for step 4) (i.e. capacitor voltage versus time).

 

Resistor voltage versus time

 

 

• Set up a table to record time (in multiples of the time constant) and voltage (across the resistor).

 

• Repeat steps 3) and 4) but put the voltmeter across the resistor for these measurements.

 

• Graph (G5) the results for step 7) (i.e. resistor voltage versus time).

 

 

Current versus time

 

• Set up a table to record time (in multiples of the time constant) and current (through the resistor and capacitor).

 

• Using the same setup as for the previous measurement of resistor voltage versus time repeat steps 3) and 4) but instead of recording the voltage, when the time get to the desired value, record the current reading on the ammeter.

 

• Graph (G6) the results for step 11) (i.e. current versus time).

 

 

 

Question (part of Results and Analysis)

 

Determine the amount of energy stored in the capacitor that you used in the experiment when it is fully charged.  Describe how that energy is put into the capacitor and how it is discharged from it.  (i.e. describe energy flow, source and where does it go)  Also determine the size of the plates and their spacing if your capacitor was an ‘air’ capacitor (i.e. only air between the plate).

 

 

 

 

 

At-Home Activity

 

 

The activity is to determine the values of the resistors and capacitors needed to have a RC circuit which will light a bulb in the following way:  The voltage across the bulb is to vary from 0 to 95 % of the battery voltage during the charging of the circuit for one minute.  (The bulb is to be connected across the capacitors.)

 

 

Method:

 

1)  Calculate the time constant needed.  Show how you determined it.

 

2)  You must use two resistors in parallel and two capacitors in series in order to get your desired time constant.  In doing this use only standard values available for resistors and capacitors — look up the standard values available!

 

3)  If the bulb is discharged using the same resistors and capacitors, determine how long it will take for the voltage to drop to 5 % of its starting value.

 

4)  You should check your results by using the circuit in the experiment.