Resistance is a measure of the the contrary to present flow in an electrical circuit.

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Resistance is measure in ohms, symbolized by the Greek letter omega (Ω). Ohms are named after Georg Simon Ohm (1784-1854), a German physicist that studied the relationship between voltage, current and also resistance. The is credited for formulating Ohm\"s Law.

All products resist present flow to some degree. They fall into among two large categories:

Conductors: products that sell very small resistance whereby electrons have the right to move easily. Examples: silver, copper, gold and aluminum.Insulators: materials that existing high resistance and restrict the circulation of electrons. Examples: Rubber, paper, glass, wood and plastic.
Gold cable serves as an excellent conductor

Resistance dimensions are normally taken to suggest the problem of a component or a circuit.

The greater the resistance, the reduced the existing flow. If abnormally high, one possible cause (among many) can be damaged conductors due to burning or corrosion. All conductors provide off some degree of heat, therefore overheating is an issue often associated with resistance.The lower the resistance, the higher the present flow. Possible causes: insulators damaged by moisture or overheating.

Many components, such together heating elements and also resistors, have a fixed-resistance value. These values are frequently printed ~ above the components\" nameplates or in manuals for reference.

When a tolerance is indicated, the measure up resistance value should be within the specified resistance range. Any far-ranging change in a fixed-resistance worth usually indicates a problem.

\"Resistance\" may sound negative, yet in electrical power it deserve to be supplied beneficially.

Examples: present must battle to circulation through the tiny coils the a toaster, enough to generate warm that browns bread. Old-style incandescent irradiate bulbs force current to circulation through filaments for this reason thin the light is generated.

Resistance cannot be measured in an operating circuit. Accordingly, troubleshooting technicians frequently determine resistance by acquisition voltage and also current measurements and applying Ohm\"s Law:

E = ns x R

That is, volts = amps x ohms. R represents resistance in this formula. If resistance is unknown, the formula can be convert to R = E/I (ohms = volts split by amps).

Examples: In an electric heater circuit, as illustrated in the 2 illustrations below, resistance is figured out by measure circuit voltage and current, then applying Ohm\"s Law.

example of common circuit resistance
example of increased circuit resistance

In the first example, full normal circuit resistance, a known reference value, is 60 Ω (240 ÷ 4 = 60 Ω). The 60 Ω resistance can assist determine the condition of a circuit.

In the second example, if circuit current is 3 amps instead of 4, circuit resistance has increased from 60 Ω to 80 Ω (240 ÷ 3 = 80 Ω). The 20 Ω acquire in full resistance can be caused by a loosened or dirty connection or one open-coil section. Open-coil sections increase the total circuit resistance, which lessened current.

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Reference: Digital Multimeter principles by glenn A. Mazur, American technical Publishers.