Electrical power

 Electrical power

Electrical power is generally defined that it is the product of current and voltage in an electric circuit. But it does not clear the concept. Although, Electric power is the rate at which electric energy is consumed in an electric circuit. It tell us how fast a electric circuit is consuming energy.

Electric energy is usually converted into another form of energy so that it can do some useful work.
Like in motor, electrical energy is converted into rotational mechanical energy.

In heater, electrical energy is converted into heat energy.
In electric bulb, electrical energy is converted into light energy etc.
It is clear that an electrical device or circuit consume input electrical energy and convert it into another form of energy.

Now the question is how fast the electrical energy is consumed by electrical device or circuit?
Electrical energy consumed in a given time is different for different devices or circuits. It depends on its resistance, its types, its function etc. Some devices consumed more electrical energy and some devices consumed Less electrical energy in the same interval of time.
Therefore, the term which is used to find the electrical energy consumed by Electrical device/circuit in the given amount of time is known as electric power.
  In simple word, electric power tell us how fast an circuit or device convert electric energy to another use-full form of energy. Electrical appliances are rated in term of electrical power, greater the the power rating of the device faster it will consume electrical energy.

For example, we have two bulb, one of 100 watt and another of 200 watt,
– 100 watt bulb consume 100J of electrical energy and convert it into heat + light energy every second.
– 200 watt bulb consume 200J of electrical energy and convert it into heat + light energy every second.

Therefore electrical energy consumed in each second is more for 200 watt bulb. It simply means that electric power is the measure of how fast the electrical energy is consumed in by and electrical circuit.

Calculation of electrical power?

As we discussed that power is rate at which electrical energy is consumed in an electric circuit
Electrical power = electrical energy consumed / time
When a charge moves from one terminals of battery to another terminals it losses  electrical potential energy of ‘qv’ Joule.
As the energy loss in circuit is the energy consumed by a circuit is
Electrical power = qv/t
As   I = q/t hence q = It
Electric power = (It)V/t
Electric Power = VI watts
P = I2R  or P = V2/R
‘I’ represent current and measured in ampere.
‘V’ represent voltage and  measured in volt.
‘R’ represent Resistance and measured in ohm.
‘P’ represent power and measured in watt.

Unit of Electrical power

Electrical power is the product of Voltage and Current,
P = V × I
If V is measure in volt and I is measured in ampere the electric power is measured in watt.

Therefore, unit of electrical power is watt.

1 watt =  1 joule/ 1 second
Electric power is also measured in joule per second.

Electric power of an circuit is said to be one watt if  of ampere of electric current flow through it when is potential difference of one volt is applied across it.

Bigger unit of electric power
1 kW (one kilowatt) =  1000 watts
1 MW (one megawatt) = 10^6 watts
1 HP (horsepower) = 746 watts
Example: An electric bulb having a resistance of 400 ohm is connected across a rated supply voltage of 220 Volt. Calculate the electric power delivered by bulb.

Given that,
Resistance of heater, R = 400 ohm
Supply voltage, V = 220 V
Electric power delivered = ?

As we know that,
Electrical Power = VI = I2R = V2/R = (220 × 220)/400 = 121 watts
Therefore, the power delivered by electric bulb is 121 watts.

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