1. Principles of Technology Waxahachie High School Ratein Electrical Systems PIC Chapter 3.3 Ratein Electrical Systems PIC Chapter 3.3 PT TEKS

2. Rate in Electrical Systems : Objectives:   Define electrical current as a rate   Describe what is measured by ammeters and voltmeters   Explain how to connect and ammeter and a voltmeter in a electrical circuit   Explain why electrons travel at speeds much lower than the speed of light in a conductor   Define frequency and period   Explain the relationship between frequency and period : Objectives:   Define electrical current as a rate   Describe what is measured by ammeters and voltmeters   Explain how to connect and ammeter and a voltmeter in a electrical circuit   Explain why electrons travel at speeds much lower than the speed of light in a conductor   Define frequency and period   Explain the relationship between frequency and period

3. 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. Rate in Electrical Systems

4. 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. Rate in Electrical Systems

5. Electric current (I) = Charge / time Charge is measured in Coulombs (C). Current is measured in Amperes (A). I = q / t Rate in Electrical Systems

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

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

8. 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. Rate in Electrical Systems

10. 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. Rate in Electrical Systems

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

13. If a wave has a frequency of 60 cycles per second (Hertz) during a 5 second interval, how many cycles or waves will occur? f = n / t 60 Hz = n / 5 s n = 60 Hz x 5 s n = 300 Rate in Electrical Systems

14. 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 Rate in Electrical Systems

15. If we have a frequency of 4000 Hz, what is the period? If we have a period of.002 s, what is the frequency? T = 1/f ; f = 1/T T = 1/4000 Hz =.0003 s f = 1/T f = 1/.002 s = 500 Hz Rate in Electrical Systems