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Energy Stored

Energy cannot be created or destroyed, but it can be saved in various forms. One way to store it is in the form of chemical energy in a battery. When connected in a circuit, energy stored in the battery is released to produce electricity.

If you look at a battery, it will have two ends: a positive terminal and a negative terminal. If you connect the two terminals with wire, a circuit is formed. Electrons will flow through the wire and a current of electricity is produced.

Energy can also be stored in many other ways. Batteries, gasoline, natural gas, food, water towers, a wound up alarm clock, a Thermos flask with hot water and even pooh are all stores of energy. They can be transferred into other kinds of energy.

Energy Transfer

In this diagram, we shall look at a bigger picture of how energy is transferred from one object to another, and from one state to the other. Take a close look and read the notes below:

A: Sun, source of solar energy. It transfers thermal (heat) and light energy to plants, humans and animals.

B: River, streams and waterfalls moving downstream are all a source or water energy (HydroPower). They are a store of kinetic energy by their movement downstream. Waterfalls also have gravitational energy.

C: Thermal and light energy from the sun is stored in plants as chemical and potential energy. When humans eat (plants) the stored energy is transferred to us. We use this energy to do work., the ball is at rest. It has potential energy but zero kinetic energy. Hitting the ball with the snooker cue means you are transferring kinetic energy from the cue to the ball.

D: Heat energy from the sun is transferred to water bodies. This warms the water up. The result is stored thermal energy. The warm water heats the air over it. Warm air rises, so the air is now set into motion. The moving air now has kinetic energy.

E: Kinetic energy in the moving air is a source of energy called Wind Energy. Wind can turn the blades and generate electrical energy, which we use in our homes.

F: Energy from the sun is captured as Solar energy by cells and panels on top of our roofs. Solar energy is then transferred into electrical energy, which we use to warm our homes and turn the TV and computers on.

Energy Dissipation

Take a look at this simple illustration of a moving ball on a snooker table...

At stage 1 stage 2 , it moves very quickly at first, and then gradually slows down at stage 3 . This means that the kinetic energy of the ball decreases and eventually to zero when the balls come to rest.

When the cue hits the ball at

With zero external force on the ball at stage 4 , the energy of the ball must be conserved. What happened to the kinetic energy? Kinetic energy has been
dissipated through friction and the ball is at rest. Potential energy is retained.

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Energy stored, Energy Transferred and Energy Dissipation

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Energy Stored Energy cannot be created or destroyed, but it can be saved in various forms. One way to store it is in the form of chemical energy in a battery. When connected in a circuit, energy stored in the battery is released to produce electricity.

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A secondary school revision resource for AQA GCSE Physics about energy transfers and efficiency, including types of energy, Sankey diagrams and how to calculate efficiency.

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Introduction

What does it mean to have energy? Well, think about how you feel when you wake up in the morning. If you have lots of energy, that probably means you feel awake, ready to go, and able to do what needs to be done during the day. If you have no energy (maybe because you didn't get your eight hours of sleep), then you may not feel like getting out of bed, moving around, or doing the things you need to do.

While this definition of energy is an everyday one, not a scientific one, it actually has a lot in common with the more formal definition of energy (and can give you a helpful way to remember it). Specifically, energy is defined as the ability to do work - which, for biology purposes, can be thought of as the ability to cause some kind of change. Energy can take many different forms: for instance, we're all familiar with light, heat, and electrical energy.

Here, we'll look at some types of energy that are particularly important in biological systems, including kinetic energy (the energy of motion), potential energy (energy due to position or structure), and chemical energy (the potential energy of chemical bonds). Energy is never lost, but it can be converted from one of these forms to another.

Kinetic energy

When an object is in motion, there is energy associated with that object. Why should that be the case? Moving objects are capable of causing a change, or, put differently, of doing work. For example, think of a wrecking ball. Even a slow-moving wrecking ball can do a lot of damage to another object, such as an empty house. However, a wrecking ball that is not moving does not do any work (does not knock in any buildings).

The energy associated with an object's motion is called kinetic energy. A speeding bullet, a walking person, and electromagnetic radiation like light all have kinetic energy. Another example of kinetic energy is the energy associated with the constant, random bouncing of atoms or molecules. This is also called thermal energy - the greater the thermal energy, the greater the kinetic energy of atomic motion, and vice versa. The average thermal energy of a group of molecules is what we call temperature, and when thermal energy is being transferred between two objects, it's known as heat.

Potential energy

Let's return to our wrecking ball example. The motionless wrecking ball doesn't have any kinetic energy. But what would happen if it were lifted two stories up with a crane and suspended above a car? In this case, the wrecking ball isn't moving, but there is, in fact, still energy associated with it. The energy of the suspended wrecking ball reflects its potential to do work (in this case, damage). If the wrecking ball were released, it would do work by making a pancake of someone's poor car. And if the ball is heavier, the energy associated with it will be greater.

This type of energy is known as potential energy, and it is the energy associated with an object because of its position or structure. For instance, the energy in the chemical bonds of a molecule is related to the structure of the molecule and the positions of its atoms relative to one another. Chemical energy, the energy stored in chemical bonds, is thus considered a form of potential energy. Some everyday examples of potential energy include the energy of water held behind a dam, or of a person about to skydive out of an airplane.

Energy conversions

An object's energy can be converted from one form to another. For instance, let's consider our favorite example, the wrecking ball. As the wrecking ball hangs motionless several stories up, it has no kinetic energy, but a lot of potential energy. Once it is released, its kinetic energy begins to increase because it builds speed due to gravity, while its potential energy begins to decrease, because it is no longer as far from the ground. Just before it hits the ground, the ball has almost no potential energy and a lot of kinetic energy.

The same kinds of conversions are possible with chemical energy, and we see lots of examples of this in our day-to-day lives. For instance, octane, a hydrocarbon found in gasoline, has chemical energy (potential energy) due to its molecular structure, which is shown above. This energy can be released in a car engine when the gasoline combusts, producing high-temperature gases that move the engine's pistons and, ultimately, propel the car forward (kinetic energy). Part of the chemical energy is converted to the kinetic energy of the car, while part is converted to thermal energy as heat emitted from the engine.

Energy can change forms in a similar way in living organisms. For instance, energy stored in bonds of the small molecule ATP (potential energy) can power the movement of a motor protein and its cargo along a microtubule track, or the contraction of muscle cells to move a limb (kinetic energy).

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Types of energy (article) | Khan Academy

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Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

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Scientists define energy as the ability to do work. Modern civilization is possible because people have learned how to change energy from one form to another and then use it to do work. We use energy to move cars along roads and boats through water, to cook food on stoves, to make ice in freezers, and to light our homes.