What is electric power?

Answer 1

Electric power is defined as the rate at which electrical energy is transferred by an electric circuit.

Power is energy over time. For example electrical energy is watts and watts are usually measured by the hour by the utility company and the unit of power is a kilowatt hour

Answer

There is really no such thing as 'electric power', despite the term being widely used in everyday life. Power is simply a rate, the rate of doing work, or the rate of heat transfer. Work is done whenever one form of energy is converted into another form, so power applies to the all forms of energy conversion, as well as to heat transfer.

The above answer is completely incorrect to say that electrical 'energy' is expressed in watts, and that 'watts are measured by the hour'. The watt is the unit of power, while energy is expressed in joules. The answer is also incorrect to say that the unit of power is the kilowatt hour, as this is used by electricity utilities to measure energy consumption, not power! In other words, the kilowatt hour is an alternative unit for energy.

Answer 2

In the most general sense, power (measured in watts) is a quantification of the ability of an electric current to do work, such as light a bulb, turn a motor or blare sound from a speaker. For the term "power" to make sense you must refer to flowing electricity (i.e., an electric current), as opposed to electrical potential. An example of potential, which is measured in volts, would be the two prongs of an unused common wall receptacle. If you put a voltmeter across the prongs you would read 120V. But no power is being consumed since no current is flowing and no "work" is being done.

If you place an ac ammeter in line with a burning 120V light bulb that is rated at 100W, you would read approximately .833A (833 thousandths of an ampere) of current flowing. Power in watts is equal to E*I, where E (often V is used) is the voltage and I is the current in amps. [Note: This is assuming a noninductive resistive load and we're assuming RMS measurements here. If you don't know what any of that means you need to read up elsewhere on the subject.]

Thus in the above example the power being used in the circuit by the load (light bulb) would be E*I, or 120*.833 = 100 watts. Makes sense since we're using a 100W light bulb.

Important -- Note that the measurement of power is a function of the available voltage, available current-delivering and carrying capacity, and the resistance of the load. The latter will determine the amount of current (amps) the load will draw at a given supply voltage, and thus the amount of power in watts consumed.

The amount of power used in your home over the span of a month determines what amount of electrical energy consumption you will be billed for by the utility. Neglecting other possible parameters such as demand charges or time-of-day billing, etc., the number of kilowatt-hours used is what matters. A kilowatt is simply 1000 watts. A kilowatt-hour (kwh) is a kilowatt multiplied by one hour. So if you burn a 100-watt bulb for ten hours you have used one kilowatt, which normally would cost you around six to ten cents, depending on rates in your area. Same charge for using some major appliance that consumes 1000 watts for one hour, or something that uses ten watts for 100 hours.

Hope that whetted your appetite to learn more.

Further Answer

Power is simply a rate. It is the rate at which energy is converted from one form into another or the rate of heat transfer. Since energy is measured in joules, power is measured in joules per second -although, in SI, this has been given a special name, the watt. Strictly, it is incorrect to talk about 'electrical power' as there is no such thing -power is simply 'power', period! It is also incorrect to talk about 'consuming power', as power describes 'consuming energy'. By way of analogy, you can equate 'power' to speed, and 'energy' to distance.