Energy and electricity
In this collection of GCSE physics revision videos, you can learn more about electricity and energy. We will explain the ways in which energy is stored as well as the differences in electric circuits and parallel circuits. We'll show you how circuits work and the earth and neutral wires. So, scroll down to start your electricity and energy physics revision.
Energy stores: Different forms in which energy is stored, including kinetic, chemical, elastic and gravitational potential energy, and how it can be transferred.
JONNY NELSON: Energy. There are lots of different types and lots of different ways of storing it.
Chemical energy in a sparkler, elastic potential energy that fires a toy into the air, and many, many more.
NARRATOR: Energy can be transferred. But energy can never ever, under any circumstances, be created or destroyed.
Yeah, never ever.
There are though, lots of different ways to store energy including:
Kinetic energy
Internal energy
Elastic potential energy
Gravitational potential energy
Nuclear energy
Magnetic energy
Let's look at some of these in more detail.
Moving objects have kinetic energy. The more mass and speed they have, the more kinetic energy they have.
All objects have internal energy, including both thermal energy contained in the vibration of its particles and also chemical energy stored in the bonds between particles.
Elastic potential energy is stored when an elastic object changes shape in a reversible way, like a catapult. The stretching or squashing stores energy.
Gravitational potential energy is stored when an object is moved higher than or away from a gravitational field. The amount of energy stored depends on:
The vertical height of the object
The strength of the gravitational field
The mass of the object
Batteries are stores of chemical energy that create current and some objects, like a Van der Graaf generator, are statically charged,while others can be magnetised and store magnetic energy.
As mentioned, although energy cannot be created or destroyed, it can be transferred or converted from one type to another.
For instance, one object can heat another cooler object, transferring heat energy.
Energy can also be transferred mechanically through movement when the motion or position of an object changes, such as one ball hitting another on a pool table.
Mechanical waves such as sound waves or the seismic waves created in an earthquake can also transfer energy mechanically.
Electrical energy can be transferred when an electrical circuit is completed. The internal energy stored in a battery is transferred to moving charged particles in the wire.
Lamps transfer visible light and thermal radiation to the surroundings, and when an object falls to the ground, the gravitational potential energy it possessed is converted to kinetic energy.
Even food transfers energy. It contains chemical energy stored in the bonds between particles, and eating and metabolising food creates an energy conversion in the body.
In a similar way, burning an object like wood causes the internal energy in the wood to be converted into heat, sound, and light given out by the flames.
When it comes to energy, there are three main equations that we need to understand and remember:
Kinetic Energy
Kinetic energy = ½ × mass × velocity²
Because velocity is squared, it has a huge impact on the total kinetic energy.
Gravitational Potential Energy
Gravitational potential energy = mass × gravitational field strength × height
Elastic Potential Energy
Elastic potential energy = ½ × force × extension
or
Elastic potential energy = ½ × spring constant × extension²
JONNY: Energy can't be created or destroyed, but it can be and is stored and transferred.
Electric circuits: The resistance of a circuit, its relationship to current and potential difference, and how to use an ammeter and voltmeter to calculate all three.
Parallel circuits: Current and potential difference, their definitions and how they are measured. The differences between series and parallel circuits.
JONNY: Electrical circuits, they're all around us but how do they work?
NARRATOR: Let's look at a simple electrical circuit made up of a power source, a light bulb and a resistor to reduce current flow. The power source drives the charges, in this case, the electrons in the circuit and the electrons transfer energy as they pass through different components. For example, the light bulb where the energy is transferred into light and heat. The current is the rate of flow of charge. In this case, the charge is provided by the electrons, measured in coulombs per second. One amp is equal to one coulomb per second. The potential difference, or PD, is the energy change per unit of charge between two points, measured in volts. One volt is equal to an energy change of one joule per coulomb of charge. If we connect the voltmeter in parallel to the bulb, we can see how many joules of energy each coulomb of charge transfers as it travels through the bulb. It compares before and after the bulb and tells us the difference.
NARRATOR: In our series circuit, the current is constant everywhere. Each charge can only move as fast as the one in front of it. In the same way that all carriages on a train have to move at the same speed, with no one carriage moving faster than any of the others. The potential difference is shared between components because the total energy of each charge from the power source goes into driving the current through all the components. Energy is transferred to each component proportional to is resistance. So if a component has twice the resistance of another, it will receive twice the amount of energy. So twice the potential difference. Also, if we increase the resistance of our circuit by adding another resistor in series, for example, the overall resistance is increased and all the components receive less energy.
NARRATOR: Adding another light bulb in parallel gives the charge another possible route around the circuit and creates a parallel circuit. In a parallel circuit, there are two or more paths for current to flow through. Potential difference is the same across each component of the parallel circuit and the sum of the currents through each path is equal to the total current that flows from the source. If we add a resistor in parallel, it actually decreases resistance because the additional route makes the overall flow easier even though there is another resistor present.
NARRATOR: In parallel circuits, current splits at junctions, similar to a junction on a railway line where some trains go one way and other trains go the other way. This reduces the total number of trains going past on each of the two tracks, splitting the current compared to before the junction. The potential difference is the same on each loop though, because each charge still carries the same amount of energy or to stay with our example, each train still carries the same number of people.
JONNY: Circuits. Turn them on turn them off.
Using energy: Heat explained as vibrations on the molecular level transferred by conduction, convection and radiation, and how these are used to heat a home.
Domestic electricity: How circuits work and safety devices around the home, including fuses, circuit breakers, the ring main circuit, live, neutral and earth wires.
Waves
What is a wave? What are its properties? Find out more in this collection of physics revision videos where you can learn about the properties of a wave, waves as a solid, and more.
Properties of waves in a fluid: Ways to find the speed of a water wave, using a ripple tank experiment to find the frequency and wavelength.
Transverse and longitudinal waves: Young surfers help demonstrate how waves travel along their path while the particles remain in their places.
Waves in a solid: How sound travels through the tightly-packed particles of a solid faster than in air, demonstrated experimentally.
Lenses: Refracting light through convex and concave lenses and explaining the different results depending on focal length.
Black-body radiation: Emission and absorption of infrared radiation change a body's temperature, while different colours absorb and emit more or fewer wavelengths.
Forces
What is a force? A force is a push or a pull that acts on an object due to the interaction with another object. Learn more about forces and Newton's Third Law in this collection of physics revision videos.
Gravity: Why objects weigh less on the moon... and astronauts can jump much higher. The difference in gravity on other planets.
Moments, levers and gears: Turning forces and how they are calculated using the position of the pivot point. How gears work on a bike.
Newton's Third Law: Equal and opposite forces demonstrated by skaters to show the relationship between mass and acceleration - the same principle that launches rockets.
Space physics
Discover more about space physics and the solar system in this GCSE physics collection. You can learn about the life of a star and the expanding universe.
Solar System: The formation of the Earth and its Moon and why the Earth's axis is tilted.
Life cycle of a star: Elements forged in the core of dying stars make up all life on Earth.
Expanding universe: Evidence for the Big Bang in the red-shift from distant galaxies.
Magnetism and electromagnetism
What is an electromagnet? And how can it be used in everyday life? Find out more about magnetism and electromagnetismin this short physics collection.
Electromagnetism: An explanation of the magnetic field produced by current in a wire, how commutators work in generators, and the electromagnetic force equation.
Power generation: How electricity from a generator is transformed so it can be fed into the national grid and used in the home. Remembering directions with Fleming's left hand rule.
Physics practicals
Learn about physics practical experiments in this collect of revision videos. Find out more about Hooke's law, Ohm's law, motion and density.
Hooke's law: The relationship between the extension of a spring and the force applied.
The principle of moments: Balancing the clockwise and anticlockwise forces on a metre ruler.
Angles of incidence and refraction: Using ray tracing to investigate how a beam of light bends through a glass block.
Ohm's law: The connection between potential difference across a conductor and the current through it.
Motion: Measuring the average speed of an object moving down runways of differing heights.
