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Power and Energy are terms that are often used by people interchangeably. “Energy” is a term that is used to describe a variety of things, including how we heat and cool our homes, how we fuel our cars, and how we feel on any given day. Although energy cannot be seen or touched, its effects can be seen and felt when it is transmitted from one location to another. Change is brought about by energy, which can be transmitted from one item to another. It is also possible to change the shape of energy. The pace at which energy is transported is referred to as power. It is not energy, yet it is frequently confused with it. Power is described as the pace at which energy is transmitted or work is accomplished, whereas energy is defined as the capacity to execute specific physical activity or work, such as running, leaping, and so on. The watt is the most often used unit of power measurement. It is used to calculate the rate of energy transfer. Let's look at the difference between power and energy.
| Table of Contents |
Key Terms: Power, Energy, Physics, Heat, Kinetic Energy, Watt, Motion, Element, Force, Displacement
What is Power?
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The quantity of energy moved or transformed per unit of time is the definition of power in physics. The watt, equivalent to one joule per second in the International System of Units, is the unit of power. Power is referred to as an activity in some ancient writings. Power is measured in units of scalars.
Because power is constantly proportional to the amount of effort done, if a person works at different rates at different times, his power will likewise vary. This is where the average-power idea comes into play.
Work/time is a metaphor for power. The expression for power may be recast as (force*displacement)/time because the expression for labour is force*displacement. The expression for power may be recast as force*velocity because the expression for velocity is displacement/time.
The power required to move a ground vehicle is calculated as the wheel's traction force x vehicle's velocity. The product of the torque generated by a motor and the angular velocity of its output shaft determines the motor's output power. Similarly, the power expended in an electrical element in a circuit is the result of the current flowing through the element multiplied by the resistance of the element.
Power Formula
Differing Powers as an Example
Assume that A, B, and C are three mechanical devices that are all equally efficient and are designed to work on the same set. Machines A, B, and C each take 20 minutes, 30 minutes, and 40 minutes to do the identical task. We can conclude from this example that machine A has more power than machines B and C because, while all three machines have the same efficiency, machine A completes the same work faster than machines B and C.
What is Energy?
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According to physics, energy is the quantitative quality that must be delivered to a body or physical system in order to do work or heat it. Energy is a conserved quantity, which means it may be modified in form but not created or destroyed, according to the conservation of energy principle. The joule is the energy delivered to an item by the effort of moving it a distance of one metre against a force of one newton, as defined by the International System of Units (SI).
Motion is linked to all sources of energy. When a body is in motion, for example, it has kinetic energy. A tensioned device, such as a bow or spring, has the ability to produce motion even when it is at rest; its arrangement incorporates potential energy. Nuclear energy is also potential energy because it arises from the arrangement of subatomic particles in an atom’s nucleus.
There are several types of energy, including heat, potential energy, kinetic energy, electric mechanical energy, and nuclear light.
Before delving into the distinction between power and energy, it's important to understand that there are only two types of energy: renewable and non-renewable. Nonrenewable energy sources include coal and petroleum, while renewable energy sources include wind and water.
To keep alive, living organisms require energy, such as that provided by food and oxygen to humans. To function, human civilisation requires energy, which can be obtained from fossil fuels, nuclear power, or renewable energy sources. The radiant energy that Planet receives from the Sun, as well as the geothermal energy that exists within the earth, drive the climate and ecosystem processes.
Energy
Energy as an Example:
Take, for example, a bowler at a bowling alley. The bowling ball rolls toward the upright pins, transferring its energy to the pins it strikes, which are then launched into the air. The bowling ball, on the other hand, gains energy as it is sent down the lane by the bowler.
Difference Between Energy and Power
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The main points of difference between Power and Energy are tabulated below:
| Energy | Power |
|---|---|
| The capacity to accomplish work is defined as energy. It is a form of power that develops through time. | The pace at which a certain job is completed or energy is conveyed is defined as power. |
| Joules or watt-seconds are the units used to measure energy. | The watt, or joules per second, unit is used to quantify this. |
| The sign for energy is the letter 'W.' | The letter P is used to represent power. |
| Energy transforms from one state to the next. | It is impossible to change one sort of power into another. |
| The term "energy" refers to a temporal amount or component. | It is an instantaneous quantity |
| Kinetic, thermal, potential, gravitational, acoustic, electromagnetic, light, elastic, and other forms of energy exist. | Electric power, optical power, human power, and other types of power exist. |
| It is recognised that energy may be stored and utilised in the future. | The quantity of power isn't storable or can't be stored. |
| Moving a car, heating a home, lighting a night, flying an aeroplane, and so on all need energy. | Power is used in mechanical, electrical, and thermal applications, among other things. |
Power VS Energy
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Things to Remember
- We frequently use the terms "power" and "energy" interchangeably. Although energy and power are claimed to be closely connected, they are not the same thing. Despite the fact that they are both utilised in regular life, there is a big difference between them.
- Power is described as the pace at which energy is transmitted or work is accomplished, whereas energy is defined as the capacity to execute specific physical activity or work, such as running, leaping, and so on. Joules, ergs, and calories are the units used to measure energy. Watts are a unit of measurement for power, which may also be expressed as ergs per second or even Joules per second.
- To further comprehend the notion of Energy and Power, take the example of a weightlifter. Power is similar to a weightlifter's strength, but Energy is considered to be a measure of how long he can maintain that production of power. Energy output values come in joules (J), while power is calculated in terms of J/seconds.
- The power of energy does not alter when it is converted from one form to another. Energy is thought to alter its form when anything has to happen. Power is solely used to determine how quickly a change has occurred; in other words, it is defined as the rate at which energy is converted per second.
Sample Questions
Ques. What is Power? (5 Marks)
Ans. We can define power as the rate at which work is completed or the amount of work completed in a given amount of time. The watt (W) or J/secis the SI unit of power. Horsepower is a metric for measuring the power of automobiles and other machines. It's about the same as 745.7 watts.
The rate at which work is done on an object is defined as power. Power is a metric that is measured over a period of time. The quantity work involves a force that causes a displacement. The period of time that this force acts to generate the displacement has nothing to do with work. Sometimes the task is completed fast, and other times it is completed more slowly. A rock climber, for example, takes an unusually long time to raise her body a few metres up the side of a cliff. A trail hiker, on the other hand, who chooses the simpler path up the mountain, may raise her body a few metres in a short length of time. Although the two people undertake the same amount of labour, the hiker completes it in significantly less time than the rock climber.
Power is a quantity that has to do with the rate at which a specific amount of work is completed. The hiker’s power rating is higher than the rock climber’s.
The pace of accomplishment of a certain work is referred to as power. It’s all about the work-to-time ratio.
Power has something to do with how quickly work is completed. The formula for calculating power is given below.
Work / Time = Power
W / t = P
Because the Joule is the standard metric unit for work and the second is the standard metric unit for time, the standard metric unit for power is a Joule / second, abbreviated W.
Ques. An item is lifted to a height of 5 metres at sea level, and then to the same height on a mountain summit 1000 metres above sea level. (3 Marks)
Is there a difference in potential energy between the two scenarios above?
Is there a difference between the potential energy of one level and the potential energy of another level?
Ans. As we ascend from the Earth's surface, we know that the value of 'g' diminishes. To put it another way, as the distance from the Earth's centre grows, the value of 'g' decreases.
As a result, the value of g on Earth's surface will be greater than the value of g' at a 1000-meter altitude. An object's potential energy is now expressed in milligrammes per metre squared.
In both scenarios, the same object is hoisted to the same height of 5 metres. As the value of g differs in both circumstances, there will be a variance in the value of their potential energy. And the potential energy of an object on the Earth's surface will be greater than the potential energy of the identical thing at a height of 1000 metres above sea level.
Ques. What's the Difference Between Electricity and Electricity? (1 Mark)
Ans. A potential difference in a circuit generates electric energy, which causes the current to flow. The pace at which electric energy is transported inside a circuit is referred to as electric power.
Ques. What is the SI Power Unit? (1 Mark)
Ans. Watt is the SI unit of power, and it is defined as Joule/second.
Ques. What is Average Power? (1 Mark)
Ans. The ratio of total energy consumed by the total time taken in consumption is what we call average power. In layman’s terms, the average power is defined as the average amount of effort or energy converted per unit of time.
Ques. A 60-watt bulb is switched on for 24 hours a day, while another 60-watt bulb is only on for 12 hours. Calculate the amount of energy used by both bulbs in a single day. (5 Marks)
Ans. Both bulbs A and B are switched on for the first 12 hours, so
Power = 60 + 60 = 120 watts
Energy = Power x Time
= 120 x 12
= 1.44 kWh (kilowatt-hour)
Now for the next 12 hours only bulb A would remain ON hence,
Power = 60 watts
Therefore, Energy is given by 0.72 kW h
Because the power consumed over the course of the day fluctuates because one bulb is switched on for just 12 hours, we must calculate average power.
We know that Average Power is equal to the total amount of energy consumed divided by the total amount of time spent.
As a result, our light bulbs' average power will be,
= (1.44 + 0.72) / 24
= 0.092 kW
You've probably observed that electrical components and energy metres in homes utilise the kWh (kilowatt-hour) unit, which stands for 1 kilowatt of electricity consumed every 1 hour, with kWh being the unit of energy.
Ques. What is Electric Power? (3 Marks)
Ans. Electric power is a physics term that refers to the rate at which electrical energy is transferred by an electric circuit per unit of time. The watt, or one joule per second, is denoted by P and measured using the SI unit of power. Electricity is frequently provided by electric batteries and generated by electric generators.
Electric Power is given by :
P = VI, in which
The letter P stands for power.
The potential difference in the circuit is denoted by V.
The electric current is I.
Ques. A resistor with a resistance of 10 ohms is linked to a 9V battery. What is the resistance's current and power? (1 Mark)
Ans. I = V/R = 9/100 = 0.9 A
Power is a product of V and I which comes out to be equal to 8.1 Watt
Ques. How can we use Ohms law to express power? (1 Mark)
Ans. P =I2R or P = V2/R are two ways to rewrite the power formula using Ohms law. Where V stands for potential difference, I for electric current, R for resistance, and P for power.
Ques. Write the different types of Power. (3 Marks)
Ans. The following are the several types of power:
- Mechanical Power- Mechanical power is the amount of energy released when a force is applied to a rigid or deformable substance.
- Electrical Power- Instead of work, electrical power refers to the amount of energy transmitted in a system or circuit per unit of time.
- Thermal Power- Heat output is the quantity of heat released into the environment per unit of time by a body.
- Sound Power-Sound power is defined as the amount of energy carried by a sound wave across a particular surface per unit of time.
Ques. What is energy? (5 Marks)
Ans. Energy is defined as the ability to accomplish work in physics. Potential energy, kinetic energy, etc. are thetypes of energy thatare all possible.
Energy can neither be created nor destroyed; it can only be changed from one condition to another. This concept is known as 1st law of thermodynamics. When a box rolls down a hill, the potential energy it possesses from being so high up is turned to the energy of motion. As the box comes to a halt owing to friction, the kinetic energy from its motion is converted to heatenergy, which warms the box and the slope.
There are different ways to shift energy to a different form. Many types of technologies, such as fuel-burning heat engines, generators, batteries, fuel cells, and magnetohydrodynamic systems, produce usable mechanical or electrical energy.
Energy is defined in terms of joules in the SI unit. A 1-newton force operating over a 1-metre distance produces 1 joule of work.
Ques. What are the types of energy? (5 Marks)
Ans. Although there are many different types of energy, Kinetic Energy and Potential Energy are the two most common. The energy in moving objects or mass is referred to as kinetic energy. Thermal energy, Sound energy, and other forms of energy are examples.
Any source of energy with stored potential that can be used in the future is referred to as potential energy. Nuclear energy, chemical energy, and other forms of energy are examples.
- Chemical Energy: Chemical energy is the energy stored in chemical compounds’ bonds (atoms and molecules). In a chemical reaction, chemical energy is released, most commonly in the form of heat. We utilise chemical energy in fuels like wood and coal, for example, by burning them.
- Electrified Energy: The energy carried by moving electrons in an electric conductor is known as electrical energy. It is a type of energy that is frequently utilised and useful. Lightning is a good example. Electrical energy can also be converted from other forms of energy. Power plants, for example, convert chemical energy held in fuels like coal into electricity through a series of transformations.
- Mechanical Energy: The energy that a substance or system has as a result of its motion is known as mechanical energy. Machines, for example, work with mechanical energy.
- Thermal Energy: The energy that a substance or system has in relation to its temperature, i.e. the energy of moving or vibrating molecules, is known as thermal energy. We use solar radiation to cook food, for example.
- Nuclear Energy: Nuclear power is a renewable energy source. Nuclear energy is the stored energy within each atom. Fusion (the process of merging atoms) or fission (the process of dividing atoms) are two ways to generate nuclear energy. The fission method is the most extensively employed.
- The Energy of Gravitation: The energy stored by an object in a gravitational field is known as gravitational energy. Water pouring down a waterfall is an example.
Ques. What is the law of conservation of energy? (3 Marks)
Ans. The Law of Conservation of Energy is arguably the most crucial law to remember while studying energy transmission. Simply put, the world’s energy supply is finite, and no new energy can be created or destroyed. This indicates that when anything loses energy, it does not completely vanish; rather, it is transferred to another object.
It’s important to remember, however, that no energy transfer is 100% efficient. Heat and sound will always lose some energy.
Ques. Differentiate between Energy and Power? (5 Marks)
Ans. It's not difficult to tell the difference between energy and power. While energy is the ability to perform labour, power is the measurement of that ability, which determines how much time the energy has been used. Well, energy is what you deliver, and power is how fast you deliver it.
The ability to do something is defined as energy. For example, energy is utilised to move a car, heat a home, illuminate the night, and even fly an aeroplane. The simplest unit of energy is the joule, but it is usually expressed in watt-hours or kilowatt-hours. Energy comes in a variety of shapes and sizes, and it is frequently stated in numerous units.
When it comes to power, it is defined as the rate of energy per unit of time. The capacity of energy that is being used is referred to as power. In simpler terms, power is the rate at which work is completed. Mechanical applications, thermal applications, electrical applications, and a variety of other sectors all require power.
Another distinction is that energy is storable, whereas power is not. Power is an instantaneous quantity, whereas energy has a time component. Power can’t be changed; it’s always the same. Meanwhile, energy builds up in predictable patterns.
Power does not change the form, but energy does. Energy must change form for something is to happen. However, Power merely indicates how quickly the shift occurred; it is the rate at which energy is converted every second.
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