Difference Between Electric Power and Electric Energy

Electrical energy is the ability to do work through electric charge movement. This type of energy results from electric charge flow. The unit of electrical energy is Joule (J) but it is measured in kilowatt-hours (kWh) for practical applications. The formula for electrical energy is E = P × t. JEE Main exam and NEET entrance exam candidates must learn about it and answer questions in the exam.

Electrical energy is the energy that originates from electric potential energy or the kinetic energy of charged particles. This is commonly known as the energy that gets converted from electric potential energy. Electrical energy is defined as energy produced through the movement of electrons from one place to another.

IIT JAM exam aspirants must understand each step in the derivation. The formula for electrical energy:

E = Pt 

Electric power P is the rate at which electrical energy is transferred or consumed in electrical circuit. Mathematically, the power is given by: 

$P = \frac{dE}{dt}$

Here: 

• P is electric power in watts (W)
• dE is differential amount of energy in joules (J)
• dt is differential amount of time in seconds (s)

Now, let us rearrange the power equation to determine the total energy E consumed or produced over a period of time.

dE = P x dt

Now, we will integrate both the sides of equation to find total energy E over specific time interval from $t_1 \text{to} t_2 ,$

${\int }_{E_1}^{E_2} dE = {\int }_{t_1}^{t_2} P dt$

Now, we can take P out of the integral by assuming that power P is constant over the time interval:

${\int }_{E_1}^{E_2} dE = P {\int }_{t_1}^{t_2} dt$

After evaluating the integral, we will get:

$E_2 - E_1 = P ( t_2 - t_1 )$

Say we assume that initial Energy $E_1$ is zero at time $t_1$ . In this case, the total energy E at time t will be 

E=P × t

Here:

• E indicates the electrical energy in joules (J) or kilowatt-hours (kWh)
• P indicates the electric power in watts (W)/ kilowatts(kW)
• t indicates the time in seconds (s) or hours (h)

Electrical power is the rate at which electrical energy is transferred by an electrical circuit. This quantifies the amount of energy consumed or produced per unit time. Electrical power is measured in watt (W), which is equal to one joule per second. CUET entrance exam must know about this formula to solve questions relevant to the exam. The electrical power formula describes the rate at which electrical energy will be transferred or consumed in an electrical circuit. The following is the formula of electrical power:

P= V × I

Here:

• P is electric power in watts (W)
• V is voltage in volts (V)
• I is current in amperes (A)

Let us take a look at the derivation of the electrical power formula useful for GATE exam and IISER exam that is derived from basic definitions of voltage and current. 

Voltage V is the work done per unit charge, i.e. V = W/Q, where W is the work done and Q is the charge.

Current I is the rate of flow of charge, i.e. I = Q/t, where Q is charge and t is time.

As per these definitions, W can be expressed as 

W = V x Q

Since power P is the rate at which work is done:

P = W/t

Now, we will substitute the expression for work done into the power equation. Therefore, we get:

$P = \frac{ V \times Q }{t}$

As per the definition of current, I = Q/t, we can substitute Q/t with I to get:

P = V x I

The relationship between electric power and energy is described by the formula:

E = Pt 

• E represents the electrical energy consumed or produced
• P indicated the electric power
• t represents time over which energy is consumed or produced

Let us understand the difference between electric power and electric energy:

Let us take a look at the FAQs related to electrical power and electrical energy: