Saint Louis University - PHYS 164Lab 6 parallel and series circuits-2.

II. Abstract The purpose of this lab is to investigate the properties of parallel and series circuits and compare these qualities and verify Ohm’s law that states that the voltage across each resistor is equal to the product of the current and the resistance of that resistor. This lab was completed by setting up three different types of circuits; a parallel circuit, a series circuit, and a combined circuit. Using an ohmmeter, a voltmeter, and ammeter, the current, voltage, and resistance of each resistor was found, and then used to calculate the total resistance. In conclusion, all the laws were verified in this lab. Ohm’s law was found to be true, that the voltage across each resistor is equal to the product of the current and the resistance, so the resistance is equal to the quotient of the III. Theory When dealing with resistors, the charge cannot distinguish between resistors; the values of each resistors are additive. The battery or charge feels the load of the total resistance of the entire circuit. This leads to the question of how the current flows through a circuit and what the voltage is across each resistor. The physical law tested in this lab is Ohm’s law, this says that for each resistor, the voltage across is equal to the product of its resistance and the current moving through it. The total voltage that a power supply or battery produces is different from what each resistor has across it. The Ammeter measures the current through a resistor by connecting in series with it, and the Voltmeter measures the voltage across a resistor by connecting in parallel with it. For a series circuit, the resistors are lined so that there is only one path that the current can take. The total current is constant throughout the entire circuit due to the law of the conservation of charge and doesn’t depend on the resistor it is moving through. Kirchhoff’s loop rule states that the sum of the voltages across the resistors is the same as the voltage of the power supply. The total resistance, Rt, that the power supply sees is the sum of each resistor, R1, R2, and R3: Rt=R1+R2+R3 . For a parallel circuit, the current has different paths it can take due to divergences in the path. The voltage across each resistor is the same because each resistor is connected to the same power supply. Ohm’s law allows for the calculation of the current through each resistor, and the sum of these currents is equal to the current through the power supply. Total resistance, Rt, is equal to the sum of the reciprocals of each resistor, R1, R2, and R3, as shown in the equation 1R t = 1R 1 + 1R 2 + 1R 3 . For any closed circuit, Kirchhoff’s law applies. This law is saying that the sum of the currents entering a node must be equal to the sum of the currents leaving said node. This law also says that the sum of the voltage changes around a closed loop is zero. These sums can be expressed in the equation