Physics Power Definition its Units, Formulas and Types

Definition:

Energy is the ability to carry out a specific task. Power is a term used to describe the amount of Energy used for doing work in a given amount of time. The symbol for it is P.

Unit:

The standard metric unit of work is the joule and the standard metric unit of time is the second, so the standard metric unit of power is the joule/second (J/s), defined as watts and abbreviated as "W". Sometimes the power of cars and other machines is expressed in horsepower (hp), which is approximately equal to 745.7 watts.

Formula:

Power is defined as the rate at which an object is worked on. 
P = Work / Time

P = W/t

The formula of "P" for different ratios:

P=VI

The formula was developed by a great scientist named Ohm and this is named after him and is also known as Ohm's law.

Where,

V = potential difference

I = current.

Electric formula

P = R × I^2 or V^2/ R

The above equations are a variation of Ohm's law.

Where,

R = resistance

V = potential difference

I = current.

power equation

P = E/t

Where,

E = "E" in joules

t = time

P = weight/t

This formula is derived from the work-energy theorem

Where,

W = work in joules

t = time

P = F × s/t

In this formula, F = force applied to an object, s = movement of an object, and t = total elapsed time.

What is Average Power?
We can define average power as the total "E" consumption divided by the total elapsed time. In simple terms, we can say that the average power is the average amount of work or energy converted per unit of time.

P _avg = ∆ W /∆ t

What is Instantaneous power?

It is defined as the energy delivered or used at a certain moment in time. It is an indicator of how quickly energy is being changed or transmitted at any given time. 

The instantaneous power (P) can be written as follows in mathematics:

P (t) = V I (t)

There are different types of power that are often discussed in different fields and contexts. Here are some of the main types:

Electricity: Electricity refers to the rate at which electrical energy is transferred or consumed. It is usually measured in watts (W) and is required by various electrical devices and systems.

Mechanical Horsepower: It is the rate at which mechanical work is done or energy is transferred in a mechanical system. It is often used to describe the power of motors, motors, and other mechanical devices. It is also measured in watts (W) or (hp).

Thermal Output: Thermal output, also known as heat output, is the rate at which heat energy is generated or transferred. It is often used in the context of power plants and heating systems where thermal energies are converted into other forms of energy.

Radiated power: It refers to the rate at which electromagnetic radiation (such as light or radio waves) is transmitted, transmitted, or received. It is measured in units such as watts (W) or in radiometric units such as radiant flux.

Solar: It is a special form of radiant energy received from the sun. It is the conversion of sunlight into usable electrical or thermal form using technologies such as solar panels or solar thermal collectors.

Wind Energy: It is the kinetic energy of moving air masses that is converted into electrical or mechanical energy. Wind turbines capture wind "E" and convert it into usable forms of energy.

Nuclear Power: It involves the production of electricity through controlled nuclear reactions such as nuclear fission or nuclear fusion. It uses the energy released by the nucleus of an atom.

 Hydraulic power: It is the use of pressurized fluids (usually oil or water) to generate mechanical power. It is used in machines and hydraulic systems such as hydraulic hoists or hydraulic brakes.

Benefits of the power formula:

The formula offers many benefits such as

The power formula helps us determine the work done by a specific object or person at a specific time.
This helps determine which item is more efficient and which is less efficient. For example, if x and y do the same activity and x completes it in 3 hours and y completes the same activity in 6 hours. This proves that "x" is the more effective option than "y".This is merely a result of x having more power than y.

 Examples:

Q1. An electric machine works in 10s using 200 J. How much "E" does it consume?

Work done = W = 300 J, thus.

Time t = 10 seconds

P = W/T

P = 200 / 10

P = 20 Watts.

Q2. Ram, who weighs 60 kg, can jump 12 meters in 40 seconds. Determine his power.

Answer: Assuming m (mass) = 60 kg,

12 meters tall,

Time taken, t, is 40 seconds.

P = W / T

P= mgh / t

P = 60 x 9.8 x 12 / 40 =588 Watts

Q3. A 60-watt bulb burns 24 hours a day, while another 60-watt bulb burns for only 12 hours. Calculate how much energy both lamps consume in one day.

Solution:

So during the first 12 hours, both lights A and B are on

Power = 60 + 60 = 120 watts.

E = power x time

= 120 x 12

= 1.44 kWh (kilowatt hours)

For the next 12 hours, only lamp A is lit, so

Power = 60W

Energy = 60 x 12 = 0.72 kWh

In this scenario, the power consumption varies during the day because a bulb is only on for 12 hours, so we need to calculate the average power,

Average power = total energy consumed / total elapsed time

Therefore, the average power of our lamps will be,

= (1.44 + 0.72) / 24

= 0.092kW

You may have noticed that electrical components and energy meters in homes use a unit of measurement called kWh (kilowatt hours), meaning 1 kilowatt of power is consumed every hour, where kWh is the unit of energy.