Introduction
The relation between the potential difference, electric current, and resistance are represented in the Ohm Law. The Ohm Law consists in the direct relation between the potential difference and the electric current of a basic circuit, where the resistance is the constant value in the relation. Mathematically speaking the Ohm Law is a first-grade equation where the potential difference is the dependent variable, the electric current the independent variable and the resistance a constant value.
With a deep analysis of the circuit, the resistances are components inside the circuit that difficult the path of the electric current through the circuit. In theory, all the components of the circuit have a resistance higher than 0 ohms. The resistance of a component is directly proportional to the material and the length and inverse to the transversal area. For example, the conductor wire represents a resistance inside the circuit when a longer cable has a higher resistance than a shorter one. Comparing two wires with similar geometries, the material, and the temperature may change the resistance conditions. A silver conductor will have less resistance than a steel conductor. The array of the resistances could change the overall resistance in the circuit. Two or more resistors in a series array will result in an equivalent resistor that adds the values of the components. Two or more resistors in a parallel array will result in an equivalent resistor that adds the inverse values of the components .
Method
1. The configuration of the circuit consists in the use of a battery (source) with an amperemeter (in the series array) and a resistor. The resistor has a parallel array a voltmeter.
2. It is necessary to consider the precision of the instruments for the experiment. From the perimeter and voltmeter, it is necessary to consider the least precise value for calculations.
3. For each resistor, the student takes note of the current value. The procedure repeats for the seven resistors.
Considering that, the experiment uses a battery with a fixed value of potential difference; there is an only value of current per each resistance as shown in Table 1.
Figure 1: Circuit diagram
Figure 2: Graph
Conclusion
The Ohm Law shows the relation between the potential difference and the electric current. The Ohm Law has a constant value in the mathematical relation represented by the resistance. The resistance, in normal conditions, does not change with a variation of the potential difference. The resistance value depends on of the material, temperature and geometric conditions of the electric components of the circuit. The resistance is directly proportional to the length and inversely proportional to the cross section of the component. For a successful laboratory experience, it is necessary to configure the circuit according to Figure 1, where the amperemeter must be in a series array with the electric components and the voltmeter in a parallel array. The amperemeter a low resistance (near zero) that does not affect the measures, different to the voltmeter that has a high resistance (mathematically infinite) that does not affect the potential difference measure. The appreciation that offers the electric instruments will give the appreciation of the calculations.
Bibliography
Physics Classroom. Current Electricity - Lesson 3 - Electrical Resistance - Ohm's Law. 2015. 25 July 2016.
