Chapter 3.3 Notes Rate in Electrical Systems

Speed is the rate of change of position. Acceleration is the rate of change of velocity. Volume Flow Rate is the rate of change of volume. Mass Flow Rate is the rate of change of mass. In electrical systems, the most important rate is Current.

When a conductor joins two objects of different voltage, charge flows from the higher potential to the lower potential. The Voltage is the prime mover that causes charge to move. In a solid conductor, it is the electrons that move in the circuit. Current is a measure of the charge that passes through the area in a time interval.

The electric current (I) = Charge / time Charge is measured in Coulombs (C). Current is measured in Amperes (A). I = q / t

A current of 7 amperes occurs in 10 seconds, what is the charge moved? I = q / t 7 = q / 10 q = 7 x 10 = 70 C

You can measure current in electrical systems with an ammeter and measure potential difference (voltage) with a voltmeter.ammeter Current = Ammeter Voltage = Voltmeter

An ammeter measures Current through a circuit element. An ammeter must be placed in the conducting path so the current through the circuit is the same as the current through the ammeter. This is called a Series connection.Series

A Voltmeter measures the potential difference or voltage across a circuit. The load (light bulb) and the voltmeter are placed parallel to each other so that the voltage across the voltmeter is the same as that across the light bulb. This is called a parallel connection.parallel

Voltmeters and Batteries

Frequency is a measure of how often a pattern repeats itself. The equation for frequency = Number of Cycles / time f = n / t

If a wave has a frequency of 60 cycles per second during a 5 second interval, how many cycles or waves will occur? f = n / t 60 = n / 5 n = 60 x 5 n = 300

The Period of a repeating pattern is the time it takes for one complete cycle. The equation for period = 1/frequency T = 1/f or f = 1/T

If we have a frequency of 4000, what is the period? If we have a period of.002, what is the frequency? T = 1/f ; f = 1/T T = 1/4000 =.0003 f = 1/T f = 1/.002 = 500