Rate in the Electrical System

Rate in the Electrical System1. 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

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)

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

Rate in the Electrical System8. 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

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

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

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

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

Rate in the Electrical System

16. How is frequency calculated?

f = n / t

- f = frequency

- n = number of cycles

- t = time

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 / tf = 240 cycles / 4 secondsf = 60 Hz

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

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