dc circuits lab ohms law cett 1403

7/27/2019 DC Circuits Lab Ohms Law CETT 1403

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CETT 1403 DC Circuits

Ohms Law & Multimeter

Name:_________________________

In this experiment, you will learn how to:

1. Verify Ohms Law2. Measure current and voltage with multi-meter.3. Plot resistor curves.

Circuit you will be building:

Figure 1

Vs R

I+

V

-


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Procedure

1. Use the voltmeter to set the output of a DC power supply to 12 volts. Once set, turn off the powersupply and connect a 1.5 K resistor to the output of the power supply. Set the current knob about

half way and turn on the power supply. Use a voltmeter and measure the voltage drop across the

resistor (this should be equal to the supply voltage).

V (1.5 K) = _____________________

2. Using Ohms Law, calculate the total current I (1.5 K) that will flow through the resistor.I (1.5 K) = ______________________ (calculated)

3. Turn off the power supply. Draw a schematic showing how you would connect an ammeter inseries with the resistor to measure current. Use correct polarities, refer to diagrams in your book

if necessary, and show the schematic to the instructor prior to proceeding. Incorrect wiring maydamage the ammeter!

4. Now connect the ammeter in series with the resistor to measure current using the correct range.Turn on the power supply and record the measured current on the ammeter. How do your

calculated and measured values for total current I(t) compare?

Explain any differences.

I(1.5 K) = ___________________ (measured)

5. Turn off the power supply and replace the 1.5 K resistor with a 4.7 K resistor. The multi-metershould still be wired to measure current. Turn on the power supply and check the voltage at the

output terminals using the voltmeter to insure the voltage is still set to 12 volts. Measure the

current with the new resistor value. How did the current vary when you increased the resistance

and holding the voltage constant?

I(4.7 K) = _________________ (measured)

6. While observing the current on the ammeter, reduce the voltage with the power supply control to 8volts. What happens to the current?


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7. Next increase the voltage to 20 volts with the power supply control. How does the current changerelative to the voltage?

8. Vary the power supply from 0 20 volts in increments of 2 volts and record the current value foreach voltage in the table below. Plot your current readings against voltage settings on the piece

of graph paper provided. Label the horizontal axis as volts, and the vertical axis as current (use

correct units). Draw a best fit straight line through the set of points.

Table for 4.7 Kohm Resistor

Voltage Current

0 V

2 V

4 V

6 V

8 V

10 V

12 V

14 V

16 V

18 V

20 V


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9. Turn off the power supply and again install the 1.5 Kohm resistor in place of the 4.7 Kohm resistor.Turn on the power supply and repeat step 6. Put this resistor plot on the same graph as the

previous resistor. Clearly identify each line with each resistor and give a title to the plots.

Table for 1.5 Kohm Resistor

Voltage Current

0 V

2 V

4 V

6 V

8 V

10 V

12 V

14 V

16 V

18 V

20 V

10.How do you interpret these two plots? For a given voltage, what happens to current for the twodifferent resistors?


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dc circuits lab ohms law cett 1403

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