In physics, electric power measures the rate of electrical energy transfer by an electric circuit per unit of time. Denoted by P and measured using the SI unit of power which is watt or one joule per second. Electric power is commonly supplied by electric batteries and produced by electric generators.
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Electric Power Definition
Electric power is the rate at which work is done or energy is transformed into an electrical circuit. Simply put, it is a measure of how much energy is used in a span of time.
| Symbol | P |
| SI Unit | Watt, joule per second |
| Scalar or Vector | Scalar Quantity |
| Formula | P = VI |
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Electric Power Formula
The formula for electric power is given by
where,
P is the power
V is the potential difference in the circuit.
I is the electric current.
Power can also be written as
The above two expressions are obtained by using Ohm’s law, Where, voltage, current, and resistance are related by the following relation:
- R is the resistance in the circuit.
- V is the potential difference in the circuit
- I is the electric current
Power-Energy Formula
Since power is the rate of energy consumption, energy can directly be calculated using
\(\begin{array}{l}P=\frac{E}{t}\end{array} \) |
Where,
E is the energy consumption (in Joules)
t is the time in seconds
\(\begin{array}{l}P=\frac{VQ}{t}\end{array} \) |
Where,
- Q is the charge (in Coulombs)
- V is potential difference in volts
- t is the time in seconds
Related Physics Concepts
| Relation Between Power And Resistance |
| Relation Between Electric Field And Electric Potential |
| Dielectric Properties – Terminology, Mechanism, Applications. |
| Relation Between Ev And Joule |
Electric Power Problems
Based on the information given above, try the application problem given below:
Example:
A 9V battery is connected to a resistor having a resistance of 10 ฮฉ. What is the current and power across the resistor?
Solution:
I = V/R = 9/10 = 0.9 A
P = VI = 9 ร 0.9 = 8.1 J/s or 8.1 W
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Frequently Asked Questions โ FAQs
Define electric Power.
Write the SI unit of electric power
Write the electric power formula and explain the terms.
Is electric power a scalar quantity or vector quantity?
How can we express power using Ohmโs law?
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