How to calculate the actual voltage and power

How to calculate the actual voltage and power

The actual voltage and the actual power are measured, not calculated. According to the measured voltage, if the resistance of the load resistance is known, the power can be calculated by P = (u ^ 2) / R. but for some electrical appliances, such as television, refrigerator, computer, it is impossible to reach the equivalent resistance, so it can only be measured. If there is no power meter, the voltage and current can be measured, and then p = V * I, Calculate the power

Calculation method of electric power of 220 V alternating current. We only know the voltage and resistance of electric appliance, but not how many watts of electric appliance

Sorry, Ohm's law can only be used for pure resistance circuit. If LZ is not pure resistance circuit, it will be more considered. For example, the induction electromotive force of motor should be considered when rotating, and the equivalent resistance of inductance should be considered for high-frequency oscillator. It is better to know the current and get the best result by multiplying the voltage by the current

When the appliance is turned on for an hour, the voltage is low, the power of the appliance is low, and then the power consumption will be less, but the efficiency is also low?
For example, if the voltage of 1000W electric appliance is 220V, the power of 180V electric appliance will be lower, and then the power consumption will be less, or the power of meter will be normal

Yes, because power is the product of voltage and current, low voltage and low current will lead to low power and less electricity consumption