What is Electric Power? Definition, Formula and Types

Electric Power: Definition, Formula and Types

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Electric power is generally delivered by electric generators, yet can likewise be provided by sources, for example, electric batteries. It is normally provided to organizations and homes (as local mains power) by the electric power industry through an electric power lattice. Electric power is typically sold by the kilowatt hour (3.6 MJ) which is the result of the power in kilowatts duplicated by running time in hours. Electric utilities measure control utilizing a power meter, which keeps a running aggregate of the electric vitality conveyed to a client.

Electrical power gives a low entropy type of vitality and can be conveyed long separations and changed over into different types of vitality, for example, movement, light or warmth with high vitality productivity.

What is Electric Power? Definition, Formula and Types

Electric power, as mechanical power, is the rate of doing work, estimated in watts, and spoken to by the letter P. The term wattage is utilized informally to signify “electric power in watts.” The electric power in watts delivered by an electric flow I comprising of a charge of Q coulombs each t seconds going through an electric potential (voltage) distinction of V is

P={\text{work done per unit time}}={\frac {VQ}{t}}=VI\,


  • Q is electric charge in coulombs
  • t is time in seconds
  • I is electric current in amperes
  • V is electric potential or voltage in volts

Electric Power Explanation

Electric power is changed to different types of vitality when electric charges travel through an electric potential (voltage) distinction, which happens in electrical parts in electric circuits. From the stance of electric power, segments in an electric circuit can be isolated into two classifications:

Passive devices or loads: When electric charges travel through a potential distinction from a higher to a lower voltage, that is when customary flow (positive charge) moves from the positive (+) terminal to the negative (−) terminal, work is finished by the charges on the gadget. The potential vitality of the charges because of the voltage between the terminals is changed over to motor vitality in the gadget.

These gadgets are called aloof parts or loads; they ‘devour’ electric power from the circuit, changing over it to different types of vitality, for example, mechanical work, heat, light, and so on. Models are electrical machines, for example, lights, electric engines, and electric warmers. In rotating current (AC) circuits the course of the voltage occasionally switches, yet the current dependably spills out of the higher potential to the lower potential side.

Active devices or power sources: If the charges are moved by an ‘outside power’ through the gadget toward the path from the lower electric potential to the higher, (so positive charge moves from the negative to the positive terminal), work will be done on the charges, and vitality is being changed over to electric potential vitality from some other sort of vitality, for example, mechanical vitality or compound vitality. Gadgets in which this happens are called dynamic gadgets or power sources, for example, electric generators and batteries.

See Also: Electric Charge Definition

Electric Power Formula

Suppose, an element supplies or consumes an energy of dw joules for a time of dt second, then power of the element can be represented as,

This equation can also be rewritten as,

Subsequently, from the as the declaration of voltage and current in the condition are momentary, the power is likewise quick. The communicated power is time-fluctuating.

So, the power of a circuit element is the product of voltage across the element and current through it.

As we have already told that a circuit element can either absorb or deliver power. We speak to the ingestion of intensity by putting a positive sign (+) in the declaration of intensity. In like manner, we put a negative sign (- ) when we speak to the power conveyed by the circuit component.

Passive Sign Convention

There is a basic connection between the heading of current, extremity of voltage and indication of the intensity of a circuit component. We call this basic relationship as passive sign convention.

At the point when a present enters in a component through its terminal of positive voltage extremity, we put a positive sign (+) before the result of the voltage and current.

This implies that the element absorbs or consumes power from the electric circuit. On the other hand, when the current through the element leaves its terminal of positive voltage polarity, we put a negative sign (-) before the product of the voltage and current. This suggests the component conveys or supplies capacity to the electric circuit. .

Give us a chance to take a resistor associated crosswise over two circuit terminals. In spite of the fact that, the remainder of the circuit isn’t appeared in the figure. The polarity of the voltage drop across the resistor and the direction of current through the resistor are shown in the figure below.

The resistor is expending an intensity of vi watts as present I ampere enters in the resistor however its positive side of the dropped voltage v volt, as appeared.


Let us take a battery connected across two circuit terminals. Although, the rest of the circuit is not shown here in the figure. The extremity of the voltage drop over the battery and the bearing of current through the battery are appeared in the figure underneath. The battery is conveying an intensity of vi watts as present I ampere enters in the battery of v volt through its positive extremity terminal as appeared.


See Also: Electrical Energy Definition

Types of Electrical Power

The electrical power is mainly classified into two types. They are the DC power and the AC power.

1. DC Power

The DC power is defined as the product of the voltage and current. It is created by the power device, battery and generator.


Where P – Power in watt.
V – voltage in volts.
I – current in amps.

2. AC Power

The AC power is mainly classified into three types. They are the apparent power, active power and real power.

1. Apparent Power – The apparent power is the pointless power or inactive power. It is represented by the symbol S, and their SI unit is volt-amp.


Where S – apparent power
Vrms – RMS voltage = Vpeak√2 in volt.
Irms – RMS current = Ipeak√2 in the amp.

2. Active Power – The active power (P) is the genuine power which is disseminated in the circuit opposition.


Where, P – the real power in watts.
Vrms – RMS voltage = Vpeak√2 in volts.
Irms – RMS current = Ipeak√2 in the amp.
Φ – impedance phase angle between voltage and current.

3. Reactive Power – The power created in the circuit reactance is called receptive power (Q). It is estimated in volt-ampere responsive.


Where, Q – the reactive power in watts.
Vrms – RMS voltage = Vpeak√2 in volt.
Irms – RMS current = Ipeak√2 in the amp.
Φ – impedance phase angle between voltage and current.

The connection between the obvious, dynamic and responsive power is appeared as follows.


The ratio of the real to the apparent power is called power factor, and their value lies between 0 and 1.

See Also: Potential Difference Definition

Electric Power Conclusion

After going through the above portion of electric power formula we can now establish a Electric definition definition. I hope you enjoy when reading this article, thank you.