Rate in the Electrical System

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					Rate in the Electrical
       System
       Unit 3 Sub 3
    Rate in the Electrical System
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
    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 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
    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/t
  f = 240 cycles / 4 seconds
  f = 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

				
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