Download Lab 1 Basic Electricity

Laboratory Exercise 1: Basic Electricity
Required components:
A DMM
Probes
One Power Supply
One Breadboard
Five Resistors (assigned randomly between 1 k and 20 k)
Part 1: Voltage measurement
Connect the probes to the meter, and set the meter so that it is suitable to measure 5 volts.
Touch the probes to the two power supply leads, and read the meter. You’ll need to wait
a few seconds while the meter makes a few guesses, and finally settles on an answer.
Write the measured value in the box below.
Measured Voltage of
a 5 V Supply
V
You might be wondering what would have happened if you had measured the power
supply backwards. Could that break your meter? No. Try it. Connect the black probe to
the positive terminal of the supply, and the red probe to the negative. You will see that
the meter gives the same answer with a negative sign. Since you measured it backwards,
it says you have a –5 V supply.
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Part 2: Resistance measurement.
To measure the resistance of a resistor, touch one probe to one of the resistor leads
(wires), and the other probe to the other lead. You can’t measure a resistor backwards
and get a negative resistance. Make sure you aren’t touching both leads with your
fingers. You can touch one, but if you touch both, it might affect you measurement. You
can’t be hurt by touching anything. It will just cause errors in your work.
Fill in the table below using five randomly chosen resistors. First, read the resistor color
code. Write the colors in the first box. Then write the resistance the code stands for in
the next box. This is called the resistor’s rated value. Finally, measure the resistor with
your meter and write this measured value in the third box. Make sure all values are in
engineering notation.
Color Code
Ex. yellow, blue, red
1
2
3
4
5
Rated Value
Measured Value
4.6 k
4.578 k
By now, you’ve noticed that the colors can be hard to read. Once you measure the
resistor, it’s easier to tell what the colors are. You’ve also noticed that resistors are never
exactly their rated value. They are just close. Some are closer than others.
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Part 3: Circuit measurement.
In this part, you will build two series circuits. The first circuit will have two resistors in
series. The second circuit will have three. For each circuit, you will calculate the current
and voltage drops, and then measure them to see how close your calculations were.
Follow the steps below for each circuit. Fill in the tables as you go.
1. Choose resistors (two for the first circuit and three for the second). Enter the rated and
measured values of the resistors in the table.
2. Build the circuit. Connect the power supply and measure the voltage across all of the
resistors (which is also the supply voltage). Write this number in the table. Note that
there is only one space for this value. It does not have to be measured for each resistor.
Disconnect the power supply.
3. Calculate the total resistance of the circuit. Enter this value in the table. Calculate the
current in the circuit. Enter this value in the table. Calculate the voltage drop across each
resistor. Enter these values in the table.
4. Connect the battery again. Measure the voltage across each resistor. Enter these
values in the table.
Circuit 1
Resistor
Measured
Resistance
()
Measured
Battery
Voltage(V)
Total
Resistance
()
Calculated
Current
(A)
Calculated
Voltage
(V)
Measured
Voltage
(V)
5V
R1
R2
R1
R2
Circuit 2
Resistor
Measured
Resistance
()
Battery
Voltage
(V)
Total
Resistance
()
Calculated
Current
(A)
Calculated
Voltage
(V)
Measured
Voltage
(V)
5V
R1
R2
R1
R2
R3
R3
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