Electric Power - Definition, Formula, Unit, FAQs

Electrical power has become an essential resource with the growth of technology in this world. It plays an important role in our everyday lives by driving appliances in households to industrial equipment. Electric power is the rate at which electrical energy is transferred into the circuit and its unit is watt. In this article, we will discuss power definition in electrical, the unit of electrical power, the electrical power formula, the power formula using Ohm's law, the power formula in terms of energy, types of electrical power, and uses of electrical power with solved problems.

What is Electric Power?

Power definition in electrical: Electric Power in an electric circuit is the rate at which work is done or energy is transformed into an electrical circuit. Power is often defined as the degree to which a task is performed. When this is done about time and the electrical circuit, it is known as electric power. Similarly, electrical energy is defined as the rate at which electricity is transferred across the electrical circuit at each time point. Electric Power is versatile - it can be generated by generators in our homes and can be supplied with batteries used in devices.

Unit of Electric Power

When you press or pull something at a certain level, you do a certain job and are represented by Joule in physics. Strength is a measure when performing any task. Watt is the unit of Electric Power. It is the degree to which a task is performed or how quickly a task is performed. One Watt is one Joule of work done on an object per second. Watt is represented as W.

OR

The energy consumed in an electrical circuit is called one Watt where one electric current ampere appears to flow in that electrical circuit. In this case, the potential difference of 1 volt is used throughout.

Another unit is the kilowatt-hour: It is the energy used when 1 kilowatt is consumed in 1 hour.

• Kilowatt (kW): $1 \mathrm{~kW}=1000 \mathrm{~W}$
• Megawatt (MW): $1 \mathrm{MW}=10^6 \mathrm{~W}$
• Gigawatt (GW): $1 \mathrm{GW}=10^9 \mathrm{~W}$

Also read:

• NCERT Exemplar Solutions for All Subjects
• NCERT Notes For All Subjects
• NCERT Solutions for All Subjects

Electric Power Formula

(1) To calculate the power, the simplest equation is the work done is divided by time.This is the power formula in terms of voltage and current.

$$
P=V I
$$

where,

• $P$ is the electric power
• $V$ is the voltage
• $I$ is the current

However, the above is mainly used for mechanical power. In terms of electricity, another equation is used when calculating a function by the amount of the electric charge and the potential difference where the charge goes.

(2)

$$
W=q V
$$

where,

$W$ is the work done or energy transferred
$q$ is the electric charge
$V$ is the electric potential difference

When we substitute (1) in (2) we get

(3) $$
P=\frac{q V}{t}
$$

where,

• $P$ is the power
• $V$ is the voltage or potential difference
• $q$ is the electric charge
• $t$ is the time

Power Formula Using Ohm's Law

Basic power formula, $P=V I$

By substituting Ohm's law, $V=I R$ in the power formula

$P=(I R) I=I^2 R$

we get, $$P=I^2 R$$

where,

• $I$ is the resistance
• $R$ is the resistance

Another formula using Ohm's law is obtained by substituting $I=\frac{V}{R}$ in the general power formula

$P=V\left(\frac{V}{R}\right)=\frac{V^2}{R}$

$$
P=\frac{V^2}{R}
$$

where,

$V$ is the voltage and $R$ is the resistance

Power Formula In Terms Of Energy

The relationship between power and energy is given as,

$$
P=\frac{W}{t}
$$

OR

$$
W=P t
$$

where,

• $P$ is the power
• $W$ is the energy or work done
• $t$ is the time

Types of Electrical Power

DC Power

• In DC power, current flows in a single constant direction.
• Constant current and voltage over time

AC Power

• The electric current periodically changes direction
• Current and voltage vary sinusoidally over time.
• Types of AC power: single-phase AC power and three-phase AC power

Uses of Electrical Power

1. Lighting lamps bulbs, LEDs etc...
2. Running electrical home appliances like refrigerator
3. Used in electric motors
4. Used in industrial, machines and equipment
5. Used solar power systems for converting solar energy into electrical power

Energy Problems and Answers

Q. The power used by the metal for two minutes is 18 kJ, at a power of 250 volts. Calculate Electric Current.

Here, $t = 120 \ seconds$

Energy = $18 \ kJ = 18000 \ Joules$

Power = $250 V$

Electricity = $P=\frac{W}{t}$ = $\frac{18000 \ Joule }{ 120 \ seconds}$$ = 150 \ Watt$

Hence, $Electric \ current (I) = \frac{150}{250}$

$$= 0.60 \ Ampere$$