OHM’S LAW

Purpose:To build an electrical circuit by varying and measuring amperage and voltage.

Materials:DC voltmeter, DC millimeter, connecting cables, Ohm resistors (min. 1000 ohms).

Safety Precautions: Be certain to turn off all power sources before beginning. Ensure use of resistor of no less than 1000 ohms.

Introduction:

Electricity is the effect produced by the flow of electrical charges. It is studied by studying static charges and charges in motion. An electron at rest possesses the physical property of an electric force field. When in motion, an electron also possesses a magnetic force field. Electricity is the combined effect of the two force fields. By having an excess of electrons at one position and a small amount at another, electrons will flow from the position of excess to the position of deficiency. In electrical circuits, electrons flow from the negative terminal to the positive terminal. Electrons in excess will possess potential energy due to their position. The electrical potential energy is the potential energy per unit charge and is measured in volts. The rate of flow of charge is the current which is measured in amperes. Resistance is the opposition to the flow of charge and is measured in ohms. Ohm’s law demonstrates the relationship between these concepts and is written as:

V = IR

where V = potential difference

I = current

R = resistance

Procedure:

A.Determination of Resistance

Ensure that all the direct power sources are off. Study the code markings on the resistors and find one that is at least 1000 ohms. This will restrict the current, assuring that you will not get hurt. Following the circuit diagram in figure 1, connect the ammeter and resistor in series. Connect the voltmeter in parallel across the resistance. Once you have completed this have your instructor check your circuit and turn on the DC power source. Once this is done, read the amperage and voltage and record these values in Data Table 1. Lower the amperage and record data. Repeat this 3 times. Calculate the resistance for each one and record the value in Data Table 1.

B.Determination of Resistance

Using a different resistor, follow the same procedure in Procedure A and record results in Data Table 2.


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Date ______

OHM'S Law Report Sheet

Data Table 1. / Resistor = _____ohms
Trial 1 / Trial 2 / Trial 3 / Trial 4
Voltage (volts)
Current (amperes)
Resistance (ohms)
Data Table 2. / Resistor = _____ohms
Trial 1 / Trial 2 / Trial 3 / Trial 4
Voltage (volts)
Current (amperes)
Resistance (ohms)