What is the Difference Between Energy and Power?
Energy can be defined as the ability to cause a change in a physical system. This quantity is expressed in joule (J) which is equivalent to kg.m2.s-2. Power can be defined as the rate at which energy is produced or utilized. This quantity is expressed in watt (W) which is equivalent to J.s-1.
What are the 2 Basic Kinds of Energy?
In everyday life, you can see potential energy in action with gravity. The classic example is a ball that is at the top of a hill ready to roll downwards due to its gravitational pull. This type of energy can also be seen when you lift something heavy up, such as a weight. It has potential energy because it can do work for you once it comes back down again.
Examples of Potential Energy
- A ball at the top of a hill - For example, when you drop a ball out your window it has potential energy because it can do work for you as the weight is pulled toward the Earth due to gravity.
- A rock sitting on a ledge - When held in place by friction or some other means, there is an object with this type of energy ready to be transferred into kinetic energy when moving.
- The water in a dam - Water has potential energy because it is held at the top of the dam ready to be released and do work for us.
- The contents of a hot air balloon - All that hot, rising air inside the balloon has potential energy! This type of energy can be transferred into kinetic energy when it starts to move upwards through convection.
- The energy stored in food (e.g. sugars) which can be used to fuel our bodies - The sugars in your body have potential energy because they can be broken down into smaller pieces that do work for us when we need to move!
The Potential Energy Equation
The Energy Equation comes up in almost every Physical Science class, it is simple and very easy to understand. However, the equation itself is actually more abstract than some may think. The potential energy part of this equation actually defines an object's kinetic energy (energy of motion) as that point on the graph where its speed reaches 0 m/s.
K.E. = 0 when velocity is equal to zero, F = ma when mass is equal to acceleration times mass, and R = V0+at when the radius is equal to the velocity of an object multiplied by its acceleration in a curved path divided by 2pi (the Greek letter "Rho"). This all may seem very complicated, but it is actually very simple.
There are three forms of the energy equation that all have to do with kinetic or potential energy. These are:
- KE = 0 relates to the objects' speed being equal to zero m/s. This means an object can be moving at a high velocity, but as long as it is not moving, its speed is equal to zero.
- KE = mgh relates to the potential of an object at some height above the surface of the Earth of mass m. If an object falls from this point, it has gravitational potential energy which means that if released at this point, it will go through the kinetic energy of moving, which makes it speed up until its speed is 0 m/s. This is the same form of kinetic energy.
- KE=1/2mv^2 relates to both the objects' velocity and mass. The equation shows 1/2 because if you took v squared and multiplied by itself, one would get velocity squared. When you divide velocity squared by mass, it becomes kinetic energy and that is why the equation looks like this: KE = 1/2mv^2 = 1/2 × mv²/m.
Wind turbines and hydroelectric dams both generate electricity from kinetic energy. Kinetic energy is simply movement, whether it be a weight dropping to the floor or the wind rotating the blades of a turbine – both forms of energy can be transformed into electrical power!
Examples of Kinetic Energy
- A ball at the top of a hill - Looking back to the previous example, when you drop a ball out your window it has potential energy because it can do work for you as the weight is pulled toward the Earth due to gravity. It then has kinetic energy as it is falling, and finally, when the ball hits the ground all its potential energy is released at once into sound waves.
- A bike - Bikes can also be fitted with generators that allow them to generate electricity as the rider moves. The more you pedal, the more power is generated!
- A wind turbine - Wind turbines use the kinetic energy of the wind to turn blades which then create electricity. This form of power is called 'renewable' because it can be used over and over again without losing its potential!
- A hydroelectric dam - Using the weight of water, these dams can produce huge amounts of electricity in a very clean way!
- An electric train - The motor in an electric locomotive drives it forward by creating motion which turns magnets around coils of wire to generate electricity.
- A car - The internal combustion engine in the car transforms chemical energy into kinetic energy which is used to turn the wheels and make the vehicle move. This form of power is called 'fossil fuel' because it requires raw materials like coal, gas, or oil which are formed over millions of years.
What is Chemical Energy?
Chemical energy is the potential of a chemical substance to undergo change through a reaction. For example, oil contains chemical energy which can be used as fuel or for other purposes.
Chemical energy is stored in the bonds of molecules. The stronger the bond, the more energy it stores, and this makes greater temperatures possible - so stronger bonds hold more potential energy than weaker ones. It takes a lot of energy to split these strong bonds apart, but when they do split apart or break they release their potential chemical energy very quickly.
What is Thermal Energy?
Thermal energy is the total of all the random motions and vibrations that atoms or molecules make in a substance. Temperature measures the average thermal energy in a substance, and it gets higher as you heat it up. Warm air, for example, has more thermal energy than cool air.
How is Thermal Energy Measured?
The SI unit for measuring heat is the joule, but you are more likely to think about temperature in degrees Fahrenheit or degrees Celsius.
What is Gravitational Potential?
Gravitational potential is a way of representing how an object will behave when it falls to Earth. It's the total amount of power that Earth has over the object, and it's often represented with an equation or graph called a "potential energy curve."
What is Elastic Potential?
Elastic potential is a way of representing how an object will behave when it's in motion. It's the total amount of power that the object has over itself. Elastic potential is also represented with an equation or graph called a "potential energy curve."
Potential Energy vs Elastic Potential
Neglecting the effects of air resistance, anything that has any amount of gravitational potential energy will have elastic potential. In other words, if something falls from a cliff to Earth, its elastic potential will decrease as it gains gravitational potential energy.
But the opposite is not true. If an object has any amount of elastic potential, it can have no gravitational potential. For example, if a rubber ball is dropped from rest, it will have some amount of gravitational potential energy once it reaches Earth's surface because gravity pulls on the ball as it falls. But because the ball is elastic, it will bounce back to its original height after it hits Earth. So the ball has no gravitational potential remaining.
But if an object is given a push off of something stationary -- say, off of the roof of a building -- then for that brief moment in time, before gravity pulls on it and brings it back down, there will be no gravitational potential. But gravity will give the object some amount of elastic potential once it reaches Earth's surface, so the object will not bounce back to its original height after impact.
So an object can have any combination of gravitational and elastic potential at a single point in time -- zero gravitational potential but non-zero elastic potential, zero both, or some amount of gravitational potential and non-zero elastic potential.
What is Activation Energy in Chemistry?
Activation energy is the minimum amount of energy needed for a chemical reaction to take place. Basically, it is the "kick" that gets the reaction over the activation energy barrier. The more difficult the barrier, the more potential there will be for higher energy products.
High activation energy indicates that there are strong bonds present between atoms in molecules and they do not break easily using the available energy in the reaction. Processes with lower activation energy usually have a more favorable equilibrium point and are thus favored under most conditions.