Mean Power
- In mains electricity, current and voltage are varying all the time
- This also means the power varies constantly, recall the equations for power:
- Where:
- I = direct current (A)
- V = direct voltage (A)
- R = resistance (Ω)
- The r.m.s values means equations used for direct current and voltage can now be applied to alternating current and voltage
- They are also used determining an average current or voltage for alternating supplies
- Recall the equation for peak current:
- Therefore, the peak (maximum) power is related to the mean (average) power by:
- Therefore, it can be concluded that:
The mean power in a resistive load is half the maximum power for a sinusoidal alternating current or voltage
Step 1: Write down the known quantities
Resistance, R = 40 Ω
Peak voltage, V0 = 240 V
Step 2: Write out the equation for the peak power and calculate
Step 3: Calculate the mean power
-
-
-
- The mean power is half of the maximum (peak) power
-
-
Mean power = 1440 / 2 = 720 W