Who Wants to Understand about Electricity and its Source?
Electric power refers to the rate per unit of time at which the electric energy is transferred by the electric circuit. If we talk about a unit of power, it is Joule per second or Joule per unit time. It is usually supplied to the homes or in the domestic mains’ electric supplies or in the offices. Electric power can be transferred to long distances with the help of transmission wires. This electric power is used for a number of purposes such as that in motion, light or heat with high efficiency.
Usually, electric power is produced by electric generators but they can be supplied to the source where it is needed with the help of the electric batteries. Electric power can be transferred to another form of energy when electric charges travel through a distance, which is popularly known as voltage. This basically occurs in electric components in the electric circuit. And on the basis of electric power, the circuits of electricity are further divided into two types. Those are active devices and passive devices.
Active devices are the sources of power while passive devices are the loads. You need to understand the law of electric power, which is the Ohm’s law. For the current to travel there is resistance also across the length of the wire test. It further depends upon different factors such as temperature, length of wires and so on. All the formulas, definitions, properties and other information need to be learnt well by the students.
What is Meant by Electric Power?
Power is commonly defined as the rate at which the work is done. When this is done with respect to time and in an electrical circuit, it is known as electric power. Alternately, electric power is defined as the rate at which electric energy is transferred across an electrical circuit per unit time. Electric power is versatile - it can be produced in generators in our houses and can be supplied to electric batteries used in devices.
Unit of Electric Power
When you push or pull something through some distance, you do some work, and it is represented by Unit Joule. Power is actually the rate at which any work is done. It is the rate at which work is done or how fast some work is done. It is the derived unit in the metric system. The Unit of Electrical Power is Watt. One Watt is one Joule of work being done on an object per second. It is defined in Joule per second. Watt is represented as W. If you do 75 Watts of work per second, it means you do 75 joules of work every second. When we calculate power, we simply consider the work and the amount of time it takes to do that work.
Voltage is the electromotive force or potential difference between two points, which signifies the amount of work required to move a charge between two points. The unit of voltage is Volt. Ampere is represented by A and is the unit of electric current.
The power consumed in an electric circuit is known as one Watt when one ampere of current is seen flowing through that electrical circuit.
In this case, the potential difference of 1 volt is applied across it.
If you want to denote a larger unit of electric power, you can use kilowatt (equal to 1000 watts).
You can also use gigawatt and megawatt for larger units of electric power.
The Formula of Electric Power
To calculate power, the most simple equation is work done divided by time.
(1) P = W/t
W is work done; t is time
However, the above expression is used mostly for mechanical power. For electric power, another equation is used, when we calculate work through the amount of charge and the potential difference through which the charge is moving.
(2) W = qV
Where q = total charge used and V = voltage
When we substitute (1) in (2), we understand that power is now the charge multiplied by the voltage divided by the time.
(3) P = qV/t
Additionally, we know that current is the charge per second that passes through the circuit at any given point in time.
(4) q = It
Where q = total charge and I = current (ampere)
Now, when we substitute (4) in (3), we understand that power is actually the current multiplied by time multiplied by voltage, divided by time. In this case, time gets cancelled from the numerator and denominator, to give us the final equation, which is :
P = IV
Here, P is the power, V or voltage is the potential difference in the circuit, and I is the electric current.
Power can also be written as
P = V2/R or I2R
Where V is the voltage, R is the resistance, and I is the electric current.
These can be obtained when we apply the Ohms law, which says that electric current is proportional to voltage and inversely proportional to resistance.
Electric Power Problems and Answers
Q1. A 280 V – 10 A electric lamp is used for 30 minutes. How much energy does it require?
Ans: In the above question,
V or Voltage = 280 Volt
I or electric power = 10 Ampere
T or Time = 30 minutes = 30 x 60 seconds = 1800 seconds
So, Electric power can be calculated.
P = IV
P = 10 x 280
P = 2800 Volt Ampere = 2800 Watt = 2800 Joule/second
However, electric energy is Electric power multiplied by time.
Electric Energy = P x t = 2800 Joule/second x 1800second = 5040000 Joule
= 5040 KiloJoule
Q2. The energy used by the iron for 2 minutes is 18 kJ, at a voltage of 250 volts. How large is the current in the iron?
Ans: Here, t = 2 minutes = 120 seconds
Energy = 18 Kilojoule = 18000 Joule
Voltage = 250 V
Electric power = P = W/t = 18000 Joule/120 seconds = 150 Watt
Therefore, Electric current (I) = P/V = 150 / 250 = 0.60 Ampere
Conclusion
Here in this article, you will learn about the definition of electric power. Here the unit of electric power is explained in detail, along with this, you will come across the formula P of electric power. There are some solutions and problems for you to solve in order to understand the topic of Electric Power well. At the end of this article, you will come across a few Frequently Asked Questions that will keep you updated with the questions that are frequently asked about these topics.
FAQs on Electric Power
1. What is electric power and how is it mathematically defined in an electric circuit?
Electric power is the rate at which electrical energy is transferred by an electric circuit. It is mathematically defined as P = VI, where P is power (in watts), V is the potential difference (in volts), and I is the current (in amperes). This relationship helps calculate how much energy is consumed or produced by electrical devices.
2. Which formulas can be used to calculate electric power using Ohm’s Law?
Electric power can be calculated using different formulas derived from Ohm’s Law:
- P = VI, where V is voltage and I is current
- P = I2R, where I is current and R is resistance
- P = V2/R, where V is voltage and R is resistance
3. What are the main types of electric power in AC circuits and how do they differ?
The main types of electric power in AC circuits are:
- Active (real) power: Power actually consumed and used, measured in watts (W).
- Reactive power: Power stored and released by inductors or capacitors, measured in volt-ampere reactive (VAR).
- Apparent power: The combined effect of active and reactive power, measured in volt-amperes (VA).
4. How do you differentiate between electric energy and electric power in practical usage?
Electric power is the rate at which work is done or energy is used, measured in watts (W). Electric energy is the total work done or energy transferred over time, measured in joules (J) or kilowatt-hours (kWh). In simple terms, power tells you how fast energy is being used; energy tells you how much has been used in total.
5. Why does increasing the resistance in a circuit lower electric power if voltage is constant?
When voltage stays the same, increasing resistance causes current to decrease (by Ohm's Law, I = V/R). Since power is P = V^2/R, as resistance increases, the denominator grows, and electric power decreases. This is because less current flows for the same voltage, reducing total energy transfer per unit time.
6. How does the choice between using kilowatt, megawatt, or gigawatt help in describing electric power in different contexts?
Larger units like kilowatt (kW), megawatt (MW), and gigawatt (GW) help describe the power output or consumption of devices ranging from homes (kW) to industries and power plants (MW/GW). This scaling avoids cumbersome numbers and gives context-appropriate measurements for practical applications.
7. What are common applications of electric power in everyday life and industries?
Electric power is used in various ways, such as:
- Lighting homes and streets with bulbs and LEDs
- Running appliances like fans, refrigerators, and washing machines
- Powering computers, mobile devices, and industrial machinery
- Operating transportation systems like electric trains
8. How does understanding electric power help in reducing electricity bills and conserving energy?
Knowing how much electric power appliances consume lets users choose energy-efficient devices and manage their usage. This helps reduce electricity bills by minimizing total energy consumption (energy = power × time) and supports environmental conservation by lowering overall demand on power stations.
9. What would happen if the current in a circuit doubled but the resistance remained constant? Explain using the power formula.
If current doubles (I becomes 2I) and resistance stays the same, power calculated by P = I2R increases by four times. This is because the square of the current (2I)² = 4I², so the circuit would consume or dissipate four times as much power, emphasizing the importance of current strength on energy use.
