Purpose
Determine the values of resistors using Ohm's law.
Concept
If voltage is placed across an object, current may flow through it. Given some
voltage, the amount of current that flows through an object is determined by the
resistance of the object. The unit of resistance is the ohm, and it represents
the resistance that allows one amp of current to flow through an object when one
volt is applied to it.
Electrical resistors are designed to provide a fixed amount of resistance.
However, temperature changes can affect the resistance of resistors.
Materials
1 ½ V Battery (or power supply), aligator clip wires, voltmeter (0 to 20 V range, DC),
milliammeter (0 to 100 mA range, DC), resistors: 100 ohm, 150 ohm and 220 ohm.
Procedure
1. Select the proper ranges on the voltmeter and ammeter. If the proper ranges are not selected, the meter can be destroyed.
2. Select a resistor and hook up in the circuit according to the diagram shown above.
3. Observe and record the voltage and current values.
4. Select a second resistor with a different color code and repeat steps 2 and 3.
5. Select a third resistor and repeat steps 2 and 3.
Analysis
1. Using the measured values, calculate the resistance of the first resistor. Is your calculated value closest to 100 ohms, 150 ohms, or 220 ohms.
2. Using the measured values, calculate the resistance of the second resistor. Is your calculated value closest to 100 ohms, 150 ohms, or 220 ohms.
3. Using the measured values, calculate the resistance of the third resistor. Is your calculated value closest to 100 ohms, 150 ohms, or 220 ohms.
4. Were your calculated values exactly the same as the theoretical values? What factor(s) could explain why not?
