Electronics/Voltage, Current, and Power - Wikibooks, open books for an open world
Charge, Current & Potential Difference in circuits. Conventional current flows around a circuit from the positive (+) side of the cell to the negative (-). Charge ( Q) – charge is measured in coulombs (C). Resistance (W) – is the ratio of potential difference across a component to the current flowing through it, it is measure. Current, Resistance, Voltage, and Power. Current Current is a measure of the flow of electric Voltage is a difference in electric potential between two points. Electric power basic formulas calculator voltage current mathematical equation formula for power law Relationship of the physical and electrical quantities ( parameters) Electric Energy is E = P × t − measured in watt-hours, or also in kWh.
In relation to "flow", the larger the "pressure difference" between two points potential difference or water pressure differencethe greater the flow between them electric current or water flow. See " electric power ". Working on high voltage power lines Specifying a voltage measurement requires explicit or implicit specification of the points across which the voltage is measured.
Ohm’s Law - How Voltage, Current, and Resistance Relate | Ohm's Law | Electronics Textbook
When using a voltmeter to measure potential difference, one electrical lead of the voltmeter must be connected to the first point, one to the second point. A common use of the term "voltage" is in describing the voltage dropped across an electrical device such as a resistor. The voltage drop across the device can be understood as the difference between measurements at each terminal of the device with respect to a common reference point or ground.
The voltage drop is the difference between the two readings. Two points in an electric circuit that are connected by an ideal conductor without resistance and not within a changing magnetic field have a voltage of zero.
Any two points with the same potential may be connected by a conductor and no current will flow between them. The various voltages in a circuit can be computed using Kirchhoff's circuit laws.GCSE Physics Revision Potential difference in series circuits
When talking about alternating current AC there is a difference between instantaneous voltage and average voltage. Instantaneous voltages can be added for direct current DC and AC, but average voltages can be meaningfully added only when they apply to signals that all have the same frequency and phase.
Relationship and Difference Between Voltage, Current and Resistance
Measuring instruments[ edit ] Multimeter set to measure voltage Instruments for measuring voltages include the voltmeterthe potentiometerand the oscilloscope. The voltmeter works by measuring the current through a fixed resistor, which, according to Ohm's Lawis proportional to the voltage across the resistor. The potentiometer works by balancing the unknown voltage against a known voltage in a bridge circuit.
The cathode-ray oscilloscope works by amplifying the voltage and using it to deflect an electron beam from a straight path, so that the deflection of the beam is proportional to the voltage. Galvani potentialElectrochemical potentialand Fermi level Inside a conductive material, the energy of an electron is affected not only by the average electric potential, but also by the specific thermal and atomic environment that it is in.
Distributions of charge density in various shapes may also yield vector E contributions to the total electric field, to be added in as vector quantities.
Practically speaking, most electricians, electrical engineers, and other electrical circuit builders and hobbyists seldom do these sorts of electric field calculations. Electric field calculations of this sort are more of a theoretical physics or special applications problem, so these calculations are omitted here in favor of more applicable material.
See Electric Field for such information on electric field formulas. There is an electrical force on a charge only if there is a charge subject to the force at a location in an electric field.
However, even if there is no such charge subject to the force, there could still be an electric field at a point. This means that an electric field is a property of a location or point in space and its electrical environment, which would determine what a charge q would "feel" if it were there.
Energy[ edit ] Now, a micro-physics review: Work is causing displacement or movement of an object or matter against a force. Energy is the ability to perform work like this.
Energy can be kinetic energy or potential energy.
Kinetic energy is the energy a mass has because it is moving. Potential energy in an object, in matter, in a charge or other situation has the ability to perform work or to be converted into kinetic energy or a different kind of potential energy. A reason why a particle or a charge may have potential energy could be because it is located at a point in a force field, such as a gravitational field, electric field, or magnetic field.
In the presence of such a field, gravity or electric or magnetic forces could cause the particle or charge to move faster or move against resistive forces, representing a conversion of potential energy to kinetic energy or work.
The amount of potential energy it has would depend on its location. Moving from one location to another could cause a change in its potential energy. For example, an object near the surface of the earth placed high would have a certain amount of gravitational potential energy based on its mass, location height or altitude in and strength of the Earth's gravitational field. If the object were to drop from this location height to a new lower location, at least some of its gravitational potential energy would be converted to kinetic energy, resulting in the object moving down.
The difference in gravitational potential energy could be calculated from one location to another, but determining the absolute potential energy of the object is arbitrary, so ground level is chosen arbitrarily as the height where its gravitational potential energy equals zero. The potential energy at all other heights is determined from the mass of the object, location relative to the ground level, and strength of the gravitational field.
All energy values are numerical or scalar quantities, not vectors. Electric Potential Energy[ edit ] Somewhat similarly, a charged particle at a certain point or location in an electrical environment i. If the charge were to move from this location to a new location or point, it could cause a change in its electric potential energy.
Current, Voltage and Power | A Level Notes
This difference in electric potential energy in the charge particle would be proportional to its charge and it could be an increase or a decrease. From measurements and calculations, one may be able to determine this difference in electric potential energy, but coming up with an absolute figure for its potential is difficult and typically not necessary.
Therefore, in a manner somewhat similar to gravitational potential energy, an arbitrary location or point nearby, often somewhere in the electric circuit in question, is chosen to be the point where the electric potential energy would be zero, if the charge were there. Often the wiring, circuit, or appliance will be connected to the ground, so this ground point is often chosen to be the zero point.
The electric potential energy at all other points is determined relative to the ground level. The SI unit of electric potential energy is the joule.
Electric Potential[ edit ] Because the electric potential energy of a charged particle or object is proportional to its charge and otherwise simply dependent on its location point where it's ata useful value to use is electric potential. Electric potential symbolized by V at a point is defined as the electric potential energy PE per unit positive charge q that a charge would have at that given point location.
At a point a, the electric potential at a is given by: On the other hand, electric potential energy is more analogous to electric force in that for it to be present, there should be a subject charged particle or object which has that energy.
Electric potential is often simply called potential by physicists. Because electric potential energy is based on an arbitrary point where its value is set at as zero, the value of electric potential at a given point is also based on this same arbitrary zero point reference point where the potential is set at zero.