3 Ohm's Law
Thursday, 12 July 2018
8:31 AM
The relationship between current and voltage is an important characteristic that defines various electronic devices. The relationship is frequently shown with a graph. Usually, the voltage is controlled (the independent variable), and the current is observed (the dependent variable). This is the basic method for this experiment, for which a series of resistors will be tested. The independent variable is plotted along the horizontal axis and the dependent variable is plotted along the  vertical axis.
Fixed resistors have a straight-line or linear current-voltage curve. This linear relationship illustrates the basic relationship of Ohm's law-namely, that the current is proportional to the voltage for constant resistance. Ohm's law is the most important law of electronics. It is written in equation form as:
𝐼=𝑉𝑅
where I represents current, V represents voltage, and R represents resistance.
Ohm's Law

Measure three resistors with listed values of 1.0 kΩ, 1.8 kΩ and 2.2 kΩ. Record the measure values in Table 2-3.

Table 2-3
Component
Listed
Value
Measured
Value
R1
1.0 kΩ
R2
1.8 kΩ
R3
2.2 kΩ
Connect the circuit shown in Figure 2-7 (a). Notice that the ammeter is in series with the resistor and forms a single "loop" as shown in the breadboard wiring diagram in Figure 2-7 (b).
Caution!
Ammeters can be easily damaged if they are incorrectly connected. Have a lab tutor check your connections before applying power.
(a) Schematic
(b) Breadboard wiring
Figure 2-7
Adjust the power supply for a voltage of 2.0 V.  Read the current through the resistor from the DMM and record it in Table 2-4.
Adjust the power supply to 4.0 V and measure the current. Record the current in Table 2-4. Continue taking current readings for each of the voltages listed in Table 2-4.
Table 2-4 (R1)
VS =
2.0 V
4.0 V
6.0 V
8.0 V
10.0 V
I =
Replace R1 with R2 and repeat steps 3 and 4. Record the data in Table 2-5.
Table 2-5 (R2)
VS =
2.0 V
4.0 V
6.0 V
8.0 V
10.0 V
I =
Replace R2 with R3 and repeat steps 3 and 4. Record the data in Table 2-6.
Table 2-6 (R3)
VS =
2.0 V
4.0 V
6.0 V
8.0 V
10.0 V
I =
In Plot 2-1, insert an Excel graph of all three I-V curves using the data from Tables 2-4, 2-5 and 2-6. To each curve, add an implied zero point (a zero voltage will produce zero current). Plot the dependent variable (current) on the vertical axis using millamps (mA) and the independent variable (voltage) on the horizontal axis using volts (V). Choose a suitable scale for the graph that spreads the data over the entire graph.
Plot 2-1
Insert your Excel graph here:
























