Experiment eight Experiment 8A: To study the Resistors in Series and Parallel Circuits DataStudio file: 08AResistors.ds Equipment List 1 PASCO interface (for two sensors) 1 Voltage Sensor 1 AC/DC Electronics Lab DC power supply3 Volt 1 Current Sensor Connect the voltage Sensor to the interface on channel A Connect the Current Sensor to the interface on channel B Introduction The purpose of this activity is to confirm that when resistors are added in series to a circuit, they have a total resistance that equals the sum of their individual resistances, and that when resistors area added in parallel to a circuit, they have a total resistance that is less than the individual resistances. Use a voltage sensor, a current sensor, and the DataStudio software to measure the voltage across parts of the series and parallel circuits and a current sensor to measure the current through the circuits. In a series circuit, devices are connected in such a way that there is the same electric current, I, through each device. The voltage, V, supplied by the source is divided among the devices. Each device has a resistance , R, that is the ratio of the voltage across the device divided by the current through the device (R = V/I). Since each device shares a portion of the voltage, V, the following describes how the voltage, current, and individual resistances are related in a series circuit: where R Total is the sum of the individual resistances. Components in a series circuit share the same current: I Total = I 1 = I 2 = . . . I n Total resistance in a series circuit is equal to the sum of the individual resistances: R Total = R 1 + R 2 + . . . R n Total voltage in a series circuit is equal to the sum of the individual voltage drops: V Total = V 1 + V 2 + . . . V n
In a parallel circuit, devices are connected in such a way that the same voltage is supplied across each device. When more than one device is connected in parallel to a voltage source, each receives current from the source as if the other device were not there. Therefore, two devices connected in parallel draw more current from the source than either device does by itself. The following describes how the voltage, current, and individual resistances are related in a parallel circuit: You can calculate the value of R Equivalent from the other individual resistances as follows: Components in a parallel circuit share the same voltage: V Total = V 1 = V 2 = . . . V n Total resistance in a parallel circuit is less than any of the individual resistances: R Total = 1 / (1/R 1 + 1/R 2 + . . . 1/R n ) Total current in a parallel circuit is equal to the sum of the individual branch currents: I Total = I 1 + I 2 + . . . I n . Setup 1. Set up the PASCO Interface and the computer and start DataStudio. Connect the Voltage Sensor and the Current Sensor into the interface.