**Power**

Most machines are created and developed to deal with objects. All machines are typically described by a power rating. The power rating indicates the rate at which that machine can do work upon other objects. Thus, the power of a machine is the work/time ratio for that specific machine. An automobile engine is an example of a machine that is given a power rating. The power rating connects to how rapidly the automobile can speed up the cars and trucks.

A person is also a machine that has a power rating. Some people are more powerful than others. That is, some people are capable of doing the exact same amount of work in less time or more function in the very same quantity of time. A typical physics laboratory involves quickly climbing up a flight of stairs and using mass, height, and time information to determine a student’s personal power.

**Definition of Power**

Power is the rate at which work is done or the rate at which energy is transferred from one place to another or transformed from one type to another. Mathematically, it is formulated using the below formula.

Power = Work/ time

P = W/ t

**Units of Power**

Power is measured in energy (joules) divided by time. The SI unit of power is the watt (W) or joule per second (J/s). Power is a scalar quantity; it has no direction. Horsepower is often used to explain the power provided by a device or a machine. A horsepower is a unit of power in the British system of measurement. It is the power needed to lift 550 pounds by one foot in one 1second and is about 746 watts.

The watt is often seen in relation to light bulbs. In this power score, it is the rate at which the bulb transforms electrical energy into light and heat. A bulb with a greater wattage will use more electrical energy per unit of time.

If you understand the power of a system, you can find the quantity of work that will be produced, as W= Pt. If a bulb has a power rating of 50 watts, it will produce 50 joules per second. In an hour (3600 seconds) it will produce 180,000 joules.

**Average Power**

When going overpower, people are normally describing average power, P _{avg}. It is the quantity of work performed in an amount of time (ΔW/ Δt) or the amount of energy transferred in a period of time (ΔE/ Δt).

**Examples of Power**

Examples of power are restricted just by the imagination because there are as lots of types as there are kinds of work and energy. Sunlight reaching Earth’s surface brings an optimal power of about 1.3 kilowatts per square meter (kW/m^{2}). A tiny fraction of this is maintained by Earth over the long term. Our usage rate of nonrenewable fuel sources is far greater than the rate at which they are stored, so it is inevitable that they will be diminished. Power indicates that energy is moved, possibly altering form.

It is never ever possible to alter one kind completely into another without losing some of it as thermal energy. For example, a 60-W incandescent bulb transforms just 5 W of electrical power to light, with 55 W dissipating into thermal energy.

Moreover, the common electrical power plant transforms just 35 to 40% of its fuel into electricity. The rest becomes a big quantity of thermal energy that must be dispersed as heat transfer, as quickly as it is created. A coal-burnt power plant may produce 1000 megawatts; 1 megawatt (MW) is 106 W of electrical power.

However, the power plant consumes chemical energy at a rate of about 2500 MW, producing heat transfer to the surroundings at a rate of 1500 MW.

### MCQs:

- What is power?
- A. The amount of energy transferred from one place to another
- B. The rate at which work is done
- C. The rate at which time is consumed
- D. The amount of energy stored in an object
**Answer: B**

- What are the units of power?
- A. Joules per meter
- B. Newtons per second
- C. Joules per second
- D. Watts per minute
**Answer: C**

- What is the SI unit of power?
- A. Joule
- B. Newton
- C. Watt
- D. Pascal
**Answer: C**

- How is horsepower defined in terms of power?
- A. It’s the power needed to lift 500 pounds by one foot in one second.
- B. It’s the power needed to lift 600 pounds by one foot in one second.
- C. It’s the power needed to lift 550 pounds by one foot in one second.
- D. It’s the power needed to lift 650 pounds by one foot in one second.
**Answer: C**

- Which of the following is a scalar quantity?
- A. Power
- B. Force
- C. Velocity
- D. Acceleration
**Answer: A**

- What does the watt measure in relation to light bulbs?
- A. Heat production
- B. Mechanical energy
- C. Electrical resistance
- D. Rate of energy transformation
**Answer: D**

- If a bulb has a power rating of 50 watts, how much energy does it produce in an hour?
- A. 50 joules
- B. 50 kilojoules
- C. 180,000 joules
- D. 180,000 kilojoules
**Answer: C**

- Which of the following is an example of power?
- A. A cup of coffee
- B. The sound of a bell
- C. Sunlight reaching Earth’s surface
- D. A ball rolling down a hill
**Answer: C**

- What is the maximum power of sunlight reaching Earth’s surface per square meter?
- A. 1.3 kilowatts
- B. 1.3 watts
- C. 1.3 megawatts
- D. 1.3 gigawatts
**Answer: A**

- What fraction of energy does a 60-W incandescent bulb convert into light?
- A. 10%
- B. 25%
- C. 50%
- D. 100%
**Answer: A**

- What fraction of fuel does a typical electrical power plant convert into electricity?
- A. 10-20%
- B. 35-40%
- C. 50-60%
- D. 75-80%
**Answer: B**

- How much thermal energy does a coal-burnt power plant produce if it generates 1000 megawatts of electricity and consumes chemical energy at a rate of 2500 MW?
- A. 500 MW
- B. 1000 MW
- C. 1500 MW
- D. 2000 MW
**Answer: C**

- What does the power rating of a machine indicate?
- A. Its efficiency
- B. Its capability to do work over time
- C. Its size
- D. Its weight
**Answer: B**

- Which term is used to explain the rate at which work is done upon other objects by a machine?
- A. Velocity
- B. Power
- C. Force
- D. Energy
**Answer: B**

- What does the work/time ratio represent for a machine?
- A. Efficiency
- B. Power
- C. Energy
- D. Speed
**Answer: B**

- In physics, what is a person considered as in terms of power?
- A. A light source
- B. A machine
- C. A force
- D. A conductor
**Answer: B**

- Which of the following is NOT a unit of power?
- A. Watt
- B. Joule
- C. Horsepower
- D. Kilowatt
**Answer: B**

- What is the relationship between power and energy transfer?
- A. They are unrelated concepts
- B. Power is the rate of energy transfer
- C. Energy transfer depends on power and time
- D. Energy transfer is the inverse of power
**Answer: B**

- What quantity does the unit “Joule per second” represent?
- A. Energy
- B. Power
- C. Force
- D. Velocity
**Answer: B**

- Which term describes the amount of energy transferred from one place to another?
- A. Force
- B. Power
- C. Work
- D. Acceleration
**Answer: B**

- What does the term “P avg” represent in power calculations?
- A. Peak power
- B. Average power
- C. Potential power
- D. Pulsating power
**Answer: B**

**Summary: Power**

**Definition, Average Power & Examples of Power**

**Definition of Power:** Power is the measure of the rate at which work is done or energy is transferred. In the realm of machines, it signifies the capability to perform work on other objects. The power of a machine is determined by its power rating, representing the work done per unit time. Similarly, individuals also possess a power rating, reflecting their ability to perform tasks over time.

**Units of Power:** Power is quantified in joules per second (watts) in the SI unit system. The watt is commonly used to describe the rate of energy conversion, such as in light bulbs.

**Average Power:** When discussing power, average power ($Pavg $) often comes into play, representing the amount of work done or energy transferred over a specific period.

**Examples of Power:** Power is demonstrated in various forms of work and energy transfer. For instance, sunlight reaching Earth’s surface carries substantial power, and even everyday objects like light bulbs showcase power by converting electrical energy into light and heat. However, the efficiency of energy conversion varies, as seen in the example of incandescent bulbs, which dissipate much of their energy as thermal heat.

Furthermore, power plants exemplify power conversion on a large scale, where only a fraction of the fuel’s energy is converted into usable electricity, with the remainder lost as thermal energy.

Understanding power is crucial for assessing energy usage, efficiency, and the impact of energy conversion processes on the environment.