Knowing how the variables are used in calculations and electrical currents is important in determining the value of the resistor and how it affects the current in the circuit. A device known as the millimeter is used to find the voltage and current in the circuit. Ohm’s principal discovery was that the amount of electric current through a metal conductor in a circuit is directly proportional to the voltage impressed across it, for any given temperature. Ohm expressed his discovery in the form of a simple equation, describing how voltage, current, and resistance interrelate: V” IR equation (1)
This continuous movement of free electrons through the conductors of a circuit is called a current (l). Current is often referred to in terms of “flow. The force motivating electrons to “flow” in a circuit is called voltage, which is a specific measure of potential energy which is always relative between two points. When there is a certain voltage present within the circuit it means the measurement of how much potential energy exists to moves the electrons from one particular point in the circuit to another particular point.
Free electrons tend to move through conductors with some degree of friction, or opposition to motion. This opposition to motion is more properly called resistance. The amount of current in a circuit depends on the amount of voltage available to motivate the electrons, and also the amount of resistance in the circuit to oppose electron flow. Just like voltage, resistance is a quantity relative between two points (scramble, born, Cromwell, and starch). There are two types of circuits namely, series and parallel.
In a series circuit the following equations are used to calculate resistance, voltage and current: ARQ RI + RE + RE + Equation (2) Equation (3) Vega = VI +VI+VI+ VI Equation (4) In parallel, the equations are a little different, 1/ARQ = I/RI + 1/RE + 1/RE Equation (5) Ice = II + 12 + 13 Equation (6) vex = VI Equation (7) Apparatus & Procedure: leg al- 12 13 Procedure of part one of this experiment was, decode the resistance values by the colors of the five resistors available to you. Once all five have been decoded, record values in excel.
Then construct a circuit using a D-cell battery, electronics lab broad and wire leads as shown in figure 3. K Once that has been completed, insert the red wire and black wire into the millimeter and insert the red on he positive side of the battery while making sure the black wire is in upper left section of the lab board. Keep in mind that the millimeter sensitivity should be at mamma range. Now you can place the resistor in the circuit to determine the readings. After determining the values of the five resistors, disconnect the millimeter in order to connect a wire from the positive end to the resistor.
Make sure to change the millimeter to voltage scale and reconnect the wires as shown in figure 3. B. Now you can measure the voltage with a resistor in the current and record these values in the table. Be sure to do this with every resistor. Part 1 sample equations: Voltage/Resistance = Current (V/R=I). In part two of this experiment, use the same equipment was in part one. Pick three resistors and insert them in the board as series as shown in figure 6. 1 below while keeping in mind that they need to be connected with additional wires to complete the circuit.
Then connect two wires to the battery cell. Put the scale back to mamma, now that the current is complete it must be interrupted by connecting the red wire to the positive terminal. Then connect the black wire to the resistor as shown figure 6. 3. Record the reading of 10 which is initial current. For parallel circuit, set the board as shown in figure 6. 4 below. Repeat the previous procedure, and interrupt the circuit in order to connect the millimeter at certain points in order to measure the currents of each resistor.
We quickly resolved this by seeking help to understand the setup. We were able to determine the current, voltage and resistance in each circuit and with the three resistors. In the series circuit by looking at table 2 under appendix A, current is the same at every resistor which shows that it follows the formula for current in series circuit as current at each point is equal. However, for voltage and resistance when one increases so does the other. It can be seen as a clear trend that with increasing voltage the resistance also increases as they are directly proportional.
The readings for each voltage are individual and the total resistance is found by the sum of all the resistors in the circuit. Looking in appendix A table 3, the table shows results for parallel circuit. The currents at O and 4 are equal or the same. The voltage is the same when going through each resistor which follows the formula in parallel circuit that each voltage equals each other. However, the resistance the inverse of each resistor is summed up to equal the total value of the resistance which is also inverses.
Thus the total resistance would be smaller than the total summed up. Looking at graph 1 in appendix A, it can be seen that as current increases the resistance decreases which follows Ohm’s law. As, I=V/R. The graph does follow the theory of this experiment. Similarly, looking at graphs it shows a relationship between WAR and current. Conclusion: can conclude that my results do agree with the theory. The results have shown that there is some type of relationship between the three variables and how hey behave in a series and parallel circuit.
It was also seen that the voltage and current had constant readings for different circuits. There was some difficulty in calculating the readings as it was rather difficult to do, due to human error and equipment error. The equipment should be more accurate with the readings and students should improve their handling on the equipment so as to obtain more accurate results. Ohm’s Law describes that current-voltage relationship for a resistor is linear. Appendices Appendix A- prediction and results of the electric field mapping.