Quantitative ideas in electricity
This can be expresses as P= VI, or watts = volts x amps. So in our analogy, power is a combination of the volume of water delivered and. This article series gives definitions of amps, volts, watts, resistance, current, ohms , relationship between electrical current (Amps), electrical voltage (Volts) and. A side note, the nice thing about the Watt, Amp, Volt, Coulomb and Second units is that they What is the practical difference between watts and VA, volt-amps?.
Glass is a good insulator and therefore a poor conductor. A third class of compounds is semiconductors. They respond to changing conditions to turn on or off the flow of electricity. Semiconductors often contain a mixture of silicon and metals.
Wafers of these semiconductors are at the heart of the "chips" in a computer, and are also the basis for LED lights and photovoltaic solar cells. For electricity to flow there must be a closed circuit. Electrons have to start out at a high-energy state and end up at a low-energy state. Below is a diagram of a simple circuit. Note that electricity flows from the high-energy end of the battery through the lamp and then back to the low-energy end of the battery.
When the switch is opened the flow of electricity stops. It is simple to think of electricity as an electron or electron-sized impulse flowing through a conductor. But in practice a single electron is way too small and carries way too little energy to do any real work. However, groups of electrons flowing together can pack a big jolt! A coulomb is 6. And an ampis a flow of one coulomb per second through a conductor.
So amps measure the rate of electricity flow. We call the flow of electricity current. Electricity does not all flow with the same force. To understand this, think about the pressure or force of water coming out of a pipe. If the pipe is attached to a reservoir at the top of a tall building, the water will have a lot more pressure than if the tank is just a foot 30 cm or so above the pipe.
It works the same way for electricity. The "pressure" of the electricity is electric potential. Electric potential is the amount of energy available to push each unit of charge through an electric circuit. The unit of electric potential is the volt. A volt is equal to a joule per coulomb. Thus, if a car battery has an electric potential of 12 volts, then it can provide 12 joules of energy for each coulomb of charge that it delivers to the starter motor.
Likewise if an outlet in your home has an electric potential of volts, then it can provide joules of energy for each coulomb of charge that is delivered to a device plugged in at the wall. For clarity purposes, we will always refer to the electric potential, which is measured in the units of volts.
Electricity, Work, and Power
High-voltage electrons arrive back to the "ground state" with more energy than low-voltage electrons. A volt is the force needed to move one amp through a conductor that has 1 ohm of resistance.
You are thinking, "There seems to be a relationship between amps, volts, and ohms" — and you are right! This is Ohm's law and is usually written as: E is electric potential measured in volts, I is current measured in amps, and R is resistance measured in ohms. The electrons flowing through the resistance of a wire are doing work. Two kinds of work performed by the current are really useful. If there is a lot of resistance in the wire, it will cause much of the work to be in the form of heat.
Think electric toaster, hair dryer, or space heater. The second really important kind of work done by the current flowing through a wire is the creation of a magnetic field. Hopefully you have played with permanent magnets when you were a kid.
You know magnets have two poles, one called north and the other called south. This naming comes from the use of magnets in compasses for finding direction.
You know that the like ends of magnets repel each other, while the opposite ends attract each other. Now, when electrical current flows through a wire, the wire becomes like a magnet in that it has a magnetic field. However, unlike permanent magnets, the magnetic field can be turned off by stopping the flow of current. This property is the basis for how electric motors function. The current going through the windings of wires in an electric motor causes the magnetism to be turned on. This then causes the motors to spin, being pulled and pushed by the attraction and repulsion of electromagnets.Understand Voltage, Ampere, Watts and Unit of Electricity
The work done by the current over time is called power. Power is measured in watts. But you know that already! Recall that above you learned that a typical human at rest is burning 80 watts. Amps measure the amount of electricity flowing over time current. Ohms measure the resistance to flow. Volts measure the amount of energy available to push each unit charge. Watt is the measure of power, or work that gets done over time.
Quantitative ideas in electricity
You know that Ohm's law states the relationship between E, I and R. But how much work is being done? That is expressed as Power.
This formula makes the point that the power depends on both the amount of electricity being delivered and how much force there is behind it. For example, a small solar panel might produce 18 volts and 2 amps. Now another solar panel could be constructed to produce 9 volts and 4 amps. Just the same as the other one! Circuits Simple Circuit Provenance: Benjamin Cuker, Hampton University Reuse: Equipment that produces and uses electricity is connected in a circuit.
The equipment can be arranged either in series or in parallel. Look at the circuits below to see the consequences of using series versus parallel arrangements. For photovoltaic PV cells, each cell can produce only about 0.
Since most applications require higher voltage, PV cells must be placed in series to produce the desired results. Electric Motors and Generators Magnetic field around a wire carrying current Provenance: Recall that part of the work done by electricity occurs when it passes through a wire to create a magnetic field.
Hans Christian Oersted discovered that in A year later Michael Faraday showed that the magnetic field around the wire can be used to create electromagnets that can be cleverly arranged to make an electric motor. Original Photo by Gina Clifford: Share — copy and redistribute the material in any medium or format Adapt — remix, transform, and build upon the material for any purpose, even commercially. Note the image of the electromagnet made by wrapping insulated wire around an iron nail.
The iron nail concentrates the magnetic field created by the current in the insulated wire. The insulation prevents the iron nail from shorting the circuit. The diagrams below show how an electric motor works. Note that at each half rotation the contacts in the commutator reverse the current to keep the motor spinning in the same direction. Images created by or credited to explainthatstuff.
Per Creative Commons License: Under CC licensing, the following are allowed: All the tutorials and material published and presented on the alternative energy tutorial website, including text, graphics and images are the copyright or similar rights of Alternative Energy Tutorials representing www.
As you have kindly asked I would have no objection to you using the image as part of your web-based energy course, free of charge. However, I must ask that you correctly reference my tutorials, images and site: Michael Faraday did not perfect the electric motor, but he did discover an important property of electromagnetism that led to another great invention, the electric generator.
Faraday discovered in the principle of magnetic induction. He found that by passing a magnet along a wire it caused the flow of electricity in a closed circuit. This led to the development of electric generators. The first successful commercial designs appeared around An electric generator is essentially an electric motor that is spun by some outside force, and in response produces induced current.
Hybrid electric cars like the Toyota Prius do exactly that. The electric motor is powered by a battery when the accelerator pedal is pressed. When the pedal is released, the momentum of the car acts through the rotating wheels to turn the motor, causing the motor to be a generator, creating electricity to recharge the battery.
Federal Aviation Administration http: This image or file is a work of a Federal Aviation Administration employee, taken or made as part of that person's official duties. As a work of the U. So far we have only considered one kind of electricity, Direct Current DC.
This is what is produced by batteries, solar panels, and DC generators. For DC electricity the current always flows in the same direction. The other kind of electricity is Alternating Current AC. As the name indicates, the current switches direction in the wire on a regular cycle. AC electricity is what comes to our homes through the power grid.
It is produced by AC generators. An AC generator is wired differently from a DC generator. Remember that in a DC generator or motor there is a commutator or rectifier that switches direction of current in coils of the armature the part that rotates.
An AC generator uses slip rings instead of the reversing commutator. As such, with each half revolution of the generator, the induced current changes directions. The output for an AC generator produces a sine wave as the electricity surges back and forth in the circuit. The reversal of current is fast. In the United States the standard for the power grid is 60 Hertz switching back and forth 60 times a second. Booyabazooka at English Wikipedia Reuse: The diagram to the right shows a sine wave produced by an AC generator.
You can even state that unit current, one ampere or ampmeans one coulomb per second in terms of copper plating 0.
Although that does not agree with the present fashion of defining currents by forces, it gives students a much easier way of picturing currents.
They already have, from common knowledge, a strong feeling for currents as streams of little electrons, and if you bunch those electrons into large coulombs of charge you can easily persuade them to think of currents being measured in coulombs per second. Defining Potential difference Once students understand energy transfers, potential difference can be discussed clearly, and the volt defined as a joule per coulomb.
Discussing power supplies as sources of energy, and electric charges as carriers of energy helps the beginner to understand why a current in a series circuit does not diminish as it flows through energy transfer components such as lamps. You can treat potential difference as a fundamental measurable quantity, described as energy transfer for each coulomb that passes through the region in question; e.
It is of course unscientific fantasy to picture coulombs carrying loads of energy on their backs and disgorging some of the load in each part of the circuit, then gathering a fresh load each time they pass through the battery. Yet if you warn students from time to time that this is an artificial picture, with unrealistic details, they can use the model to develop a useful insight into potential difference.
That is just dictionary work. And when you generate an e. Advanced level ideas In more formal treatments of electricity, unit current is chosen as the fundamental quantity defined in terms of the force between parallel currents. Resistance is a useful derived quantity, a secondary standard that can be preserved and copied easily.