Ohms law
From uCtrl.net
Contents |
Information
- I = Current, measured in Amperes (A).
- V = Voltage, measured in Volts (V).
- R = Resistance, measured in Ohms (ohms.gif).
- W = Effect, measured in Watts (W).
Current
Electrical current is a definition of the transport of electrical charges. The charge is carried by either electrons (in solid matter) or by ions (in water based matter, electrolytes).
Electrical current is measured in amps, A, and stated with I. Amperes is one of the base units in the SI-system.
When a charge, Q, passed a matter in the time, t, the current is given by:
Electrical current leads to a magnetic field surrounding the conductor.
We define the power direction from plus to minus in a load, and the other way around in a source. The fact that the electrons are moving the opposite way does not matter when doing calculations.
Voltage
Electrical voltage is a measurement of the potential difference of electrons between two points. The SI-unit for voltage is volt (V), and can be measured using a volt meter. In formulas the letter U, V or E is used. E is preferred in academic texts, so not to confuse with the unit volt, V.
If points are connected to form a electrical circuit, electrical current will come into being and try to even out the potential difference.
Voltage is not a base unit, it is defined so that one volt is the voltage required for a one amp current to give the effect of one watt.
The force between two different charges and perform work. The voltage is equal to the work the electrical energy does or. charge unit when carrying charges trough en electrical component or conductor.
Effect
In physics effect is defined as work performed pr. time unit. The measurement unit for effect in the SI-system is watt and the measurement unit for work is joule. One watt is the same as disposing of one joule pr. second.
Since one joule is the equivalent to the work of pushing one newton over a distance of one meter, one watt will be able to push a object with the force of one newton with a speed of one meter pr. second. This is equal to hoisting about 102 grams one meter up pr. second.
An older unit for effect still very much in use is horsepower. A metrical horsepower is the equivalent to 735.49875 watts, or hoisting a 75 kg object one meter up pr. second. One kW is equal to 1,36 horsepower.
