Physics Lab 2

Physics Lab 2 - Ohms Law and Electrical Currents Suneet...

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Ohm’s Law and Electrical Currents Suneet Bhansali February 3, 2010 TA: Ryan Partners: Caroline, Logan, Jennie, Trey Phys 105 Section 413 Pledge
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Abstract: In this experiment, we measure the current-voltage qualities of a resister in order to determine if they follow Ohm’s law, through the use of a multimeter. Theoretically, an electric current flows from high potential to low potential across a conductor with w potential difference. In part one, we utilize an ohmmeter to measure the resistance of three resistors, both in a series and a parallel configuration. In the second part, a current is run through a 677ohm resistor and the current and voltage were both measured using separate multimeters. The graph of current versus voltage tells us if a series is ohmic and is used to determine the linear relationship between the current and voltage. The inverse of this slope is known as the resistance. A similar test using a light bulb shows that the light bulb has a lower resistance than the 677 ohm resistor. Finally, we test a last circuit in which one resistor is in series to two parallel ones. By recording the voltage and the current through each resistor we can determine if the circuit satisfies each of Kirchhoff’s rules. Introduction In this experiment, we used a multimeter to determine the ohmic qualities of resistors in parallel and/or series configurations. By plotting the graph of a current versus voltage, the resistance can be determined. If the relationship between current and voltage is a linear, the circuit is ohmic, or it follows Ohm’s law: Potential difference (V) = Current (I) * Resistance (R). In an electrical circuit, wires alone do not have a significant resistance. Resistors provide the resistance in order to control the distribution of currents through the circuit. In this experiment, we use carbon composite resistors made up of small brown cylinders with colored bands that code for a specified tolerance. In this lab only a DC circuit was studied. This circuit was made
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up of a power source, between one and three resistors, and a multimeter all connected with wires with insignificant resistance. Kirchhoff’s loop rule is used to analyze the circuit. Kirchhoff’s loop rule states that the total change in the voltage around any closed loop is zero. The second rule states that at a junction, the amount of current flowing into the junction is equal to the amount of current flowing out of it. The two types of resistor-connections in a circuit are series and parallel. When resistors are connected in a series, Kirchhoff’s rules state that the equivalent resistance is equal to the sum of each individual resistance. R eq =R 1 +R 2 +R 3 ... According to Kirchhoff’s rules the equivalent resistance (R) of resistors in parallel is given by:
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Physics Lab 2 - Ohms Law and Electrical Currents Suneet...

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