Presentation is loading. Please wait.

Presentation is loading. Please wait.

The Effective Value of an Alternating Current (or Voltage)

Similar presentations


Presentation on theme: "The Effective Value of an Alternating Current (or Voltage)"— Presentation transcript:

1 The Effective Value of an Alternating Current (or Voltage)
© David Hoult 2009

2 © David Hoult 2009

3 © David Hoult 2009

4 © David Hoult 2009

5 © David Hoult 2009

6 © David Hoult 2009

7 If the two bulbs light to the same brightness (that is, they have the same power) then it is reasonable to consider the current Iac to be (in some ways) equivalent to the current Idc © David Hoult 2009

8 The simple average value of a (symmetrical) a.c. is equal to
If the two bulbs light to the same brightness (that is, they have the same power) then it is reasonable to consider the current Iac to be (in some ways) equivalent to the current Idc The simple average value of a (symmetrical) a.c. is equal to © David Hoult 2009

9 The simple average value of a (symmetrical) a.c. is equal to zero
If the two bulbs light to the same brightness (that is, they have the same power) then it is reasonable to consider the current Iac to be (in some ways) equivalent to the current Idc The simple average value of a (symmetrical) a.c. is equal to zero © David Hoult 2009

10 The R.M.S. Value of an Alternating Current (or Voltage)
© David Hoult 2009

11 © David Hoult 2009

12 If an a.c. supply is connected to a component of resistance R, the instantaneous power dissipated is given by © David Hoult 2009

13 If an a.c. supply is connected to a component of resistance R, the instantaneous power dissipated is given by power = i2 R © David Hoult 2009

14 © David Hoult 2009

15 © David Hoult 2009

16 The mean (average) power is given by
© David Hoult 2009

17 The mean (average) power is given by
mean power = (mean value of i2) R © David Hoult 2009

18 The mean value of i2 is © David Hoult 2009

19 I2 The mean value of i2 is 2 © David Hoult 2009

20 The square root of this figure indicates the effective value of the alternating current
© David Hoult 2009

21 The square root of this figure indicates the effective value of the alternating current
r.m.s. = root mean square © David Hoult 2009

22 © David Hoult 2009

23 where I is the maximum (or peak) value of the a.c.
Irms = 2 where I is the maximum (or peak) value of the a.c. © David Hoult 2009

24 The r.m.s. value of an a.c. supply is equal to the direct current which would dissipate energy at the same rate in a given resistor © David Hoult 2009

25 The r.m.s. value of an a.c. supply is equal to the direct current which would dissipate energy at the same rate in a given resistor We can use the same logic to define the r.m.s. value of the voltage of an alternating voltage supply. © David Hoult 2009

26 where V is the maximum (or peak) value of the voltage
The r.m.s. value of an a.c. supply is equal to the direct current which would dissipate energy at the same rate in a given resistor We can use the same logic to define the r.m.s. value of the voltage of an alternating voltage supply. V Vrms = 2 where V is the maximum (or peak) value of the voltage © David Hoult 2009

27 We have been considering a sinusoidal variation of current (or voltage)
© David Hoult 2009

28 We have been considering a sinusoidal variation of current (or voltage)
© David Hoult 2009

29 For this variation, the r.m.s. value would be
We have been considering a sinusoidal variation of current (or voltage) For this variation, the r.m.s. value would be © David Hoult 2009

30 We have been considering a sinusoidal variation of current (or voltage)
For this variation, the r.m.s. value would be equal to the maximum value © David Hoult 2009


Download ppt "The Effective Value of an Alternating Current (or Voltage)"

Similar presentations


Ads by Google