1. Rate in the Electrical System

2. 1. What is the prime mover in the electric system? - voltage 2. What is electric rate? - amount of charge that flows through a conductor in a unit of time 3. What term in given to electric rate? - current

3. Rate in the Electrical System 4. What letter is used to represent electric current? - I 5. What unit is used to measure current? - amperes (amps)

4. Rate in the Electrical System 6. What is the equation for calculating current? - Current = charge moved elapsed time - I = q t 7. When is electrical current one ampere? - when one coulomb of charge is moved in one second

5. Rate in the Electrical System 8. Example – A DC motor operates at a rate of 10 amperes for 10 seconds. How much charge moves through the motor? - I = q t - 10 amps = q 10 sec - q = 100 coulombs

6. Rate in the Electrical System 9. What is the difference between AC and DC current? - DC current flows only one way – from the negative electrode to the positive - AC current flows either way – the electrons constantly change direction

7. Rate in the Electrical System 10. Why is AC current used in homes and businesses? - it is much more economical to transfer AC current over long distances than DC current 11. How do you measure voltage in a circuit? - voltmeter - it is connected in parallel with the circuit

8. Rate in the Electrical System 12. How do you measure current in a circuit? - ammeter - it is connected in series with the circuit 13. What is a VOM? - a handheld device that measures both current and voltage

9. Rate in the Electrical System 14. What is frequency in terms of AC current? - measure of how often the current alternates 15.What unit is used to measure frequency? -hertz (Hz) – both SI and English

10. Rate in the Electrical System 16. How is frequency calculated? f = n / t - f = frequency - n = number of cycles - t = time

11. Rate in the Electrical System 17. Example – A generator produces an electrical signal that has 240 cycles in 4 seconds. What is the frequency of the signal? f = n / t f = 240 cycles / 4 seconds f = 60 Hz

12. Rate in the Electrical System 18. How are frequency and period related? - period is the time it takes for one cycle to occur f = 1 / T - T = period (usually in seconds) T = 1 / f

13. Rate in the Electrical System 19. Example – The frequency of an electrical wave is 60 Hz. What is the period of the wave for one cycle? - T = 1 / f - T = 1 / 60 Hz - T = 0.0167 sec