Umair Gaines
Electrical resistance is measured in ohms, represented by the symbol Ω, the uppercase Greek letter omega. The ohm is the standard unit of electrical resistance in the International System of Units (SI). It is named after German physicist Georg Ohm, who introduced Ohm's Law, which states that there is a proportional relationship between voltage, current, and resistance in an electrical circuit.
| Characteristics | Values |
|---|---|
| Symbol | Ω (the uppercase Greek letter omega) |
| Name | ohm |
| SI unit of | electrical resistance |
| Reciprocal quantity | electrical conductance |
| Electrical conductance measured in | siemens (S) |
| Siemens formerly called | 'mho' |
| Represented by | ℧ |
| Ohm defined as | an electrical resistance between two points of a conductor when a constant potential difference of one volt (V), applied to these points, produces in the conductor a current of one ampere (A), the conductor not being the seat of any electromotive force |
| Ohm in electronics industry | R is used instead of Ω |
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What You'll Learn
- The symbol for electrical resistance is Ω, the uppercase Greek letter omega
- Ohms are sometimes written as R, especially in the electronics industry
- The unit is named after German physicist Georg Ohm
- Electrical resistance is a measure of opposition to the flow of electric current
- Resistance is influenced by the material and shape of an object
The symbol for electrical resistance is Ω, the uppercase Greek letter omega
The ohm is defined as the electrical resistance between two points of a conductor when a constant potential difference of one volt (V), applied to these points, produces a current of one ampere (A) in the conductor, excluding any electromotive force. In simpler terms, it is the equivalent of one volt per one ampere (V/A).
In the electronics industry, it is common to use the character R instead of the Ω symbol, so a 10 Ω resistor may be represented as 10R. This is part of the RKM code and helps to avoid overlooking the decimal point, which may not be rendered reliably on components or when duplicating documents.
Ohms are sometimes expressed in power-of-10 multiples to accommodate large quantities. For example, one kiloohm is equal to 1,000 (10^3) ohms, and one megaohm is equal to 1,000,000 (10^6) ohms. Conversely, ohms can also be expressed in smaller quantities, such as the microohm, which is 0.000001 (10^-6) of a single ohm.
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Ohms are sometimes written as R, especially in the electronics industry
The ohm is the standard unit of electrical resistance in the International System of Units (SI). It is named after German physicist Georg Ohm (1789–1854). The ohm is represented by the Greek letter omega (Ω).
The ohm is defined as the electrical resistance between two points of a conductor when a constant potential difference of one volt (V), applied to these points, produces in the conductor a current of one ampere (A). This can also be understood as one volt per one ampere (V/A). In simpler terms, ohms are a measurement of how much an object resists the flow of electric current.
Ohm's law states that there is a proportional relationship between voltage, current, and resistance in an electrical circuit. This law was introduced by Georg Ohm, after whom the unit of electrical resistance is named.
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The unit is named after German physicist Georg Ohm
The ohm (Ω), the SI unit of electrical resistance, is named after German physicist Georg Ohm. Born in 1789 in Erlangen, Bavaria, Germany, Ohm was first educated by his father, Johann Wolfgang Ohm, a locksmith, in subjects including mathematics and physics. He later attended Erlangen Gymnasium, where he received little scientific training. This early education bore similarities to that of the Bernoulli family, as noted by a professor at the University of Erlangen.
Ohm's father sent him to Switzerland at age 15, where he became a mathematics teacher in Gottstadt bei Nidau. He received his doctorate from the University of Erlangen in 1811 and joined the faculty as a lecturer in mathematics. However, he left after three semesters due to low pay. Ohm then took a series of teaching positions, including one at the Jesuit Gymnasium of Cologne in 1817, where he became a professor of mathematics.
Ohm's most notable work, Die galvanische Kette, mathematisch bearbeitet (The Galvanic Circuit Investigated Mathematically), was published in 1827. In it, he laid out his law for electromotive force, stating that the current flow through a conductor is directly proportional to the potential difference (voltage) and inversely proportional to the resistance. This work greatly influenced the theory and applications of current electricity, but it was initially received with little enthusiasm.
Ohm's work eventually gained recognition, and in 1841, he was awarded the Copley Medal by the Royal Society of London. He became a foreign member of the Royal Society in 1842 and a full member of the Bavarian Academy of Sciences and Humanities in 1845. The ohm, the unit of electrical resistance, is a testament to his significant contributions to the field of physics.
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Electrical resistance is a measure of opposition to the flow of electric current
The electrical resistance of an object is a measure of its opposition to the flow of electric current. All objects resist electrical current to some degree, except for superconductors, which have zero resistance. The resistance of an object depends largely on the material it is made of. Objects made of electrical insulators like rubber tend to have very high resistance, while objects made of electrical conductors like metals tend to have very low resistance.
The resistance of a given object depends primarily on two factors: the material it is made of and its shape. For a given material, the resistance is inversely proportional to the cross-sectional area. For example, a thick copper wire has lower resistance than a thin copper wire. Additionally, for a given material, the resistance is proportional to its length. So, a long copper wire has higher resistance than a short copper wire.
The relationship between voltage, current, and resistance in an electrical circuit is described by Ohm's law, introduced by German physicist and mathematician Georg Simon Ohm. According to this law, there is a proportional relationship between voltage, current, and resistance. Ohm's law states that the voltage (V) across a circuit is equal to the current (I) flowing through it multiplied by the resistance (R). Mathematically, this can be expressed as V = I * R, or R = V/I.
Ohm's law applies to both direct current (DC) and alternating current (AC). However, measuring resistance in AC circuits differs from DC circuits due to the oscillating nature of AC. In AC circuits, the circuit's impedance must be measured, which considers resistance, inductance, and capacitance. Inductance and capacitance are also measured in ohms, and together they are referred to as the circuit's reactance.
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Resistance is influenced by the material and shape of an object
The electrical resistance of an object is a measure of its opposition to the flow of electric current. The SI unit of electrical resistance is the ohm (Ω), and it is represented by the uppercase Greek letter omega (Ω).
The geometry or shape of an object also plays a crucial role in determining its resistance. For a given material, the resistance is inversely proportional to the cross-sectional area. A thick copper wire has lower resistance than a thin copper wire of the same length and material. Additionally, for a given material, the resistance is proportional to the length. A long copper wire has higher resistance than a shorter copper wire of the same thickness. This is similar to how it is more difficult to push water through a long, narrow pipe than a wide, short pipe.
The resistance of an object is defined as the ratio of voltage across it to the current through it, and this relationship is known as Ohm's law. The proportionality between voltage and current is observed in a wide variety of materials and conditions, and the materials that satisfy this relationship are called ohmic materials. However, there are also non-ohmic materials where the current is not proportional to the voltage, and the resistance varies with voltage and current.
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Frequently asked questions
The symbol for electrical resistance is Ω, the uppercase Greek letter omega.
The unit of electrical resistance is the ohm, which is named after German physicist Georg Ohm.
The ohm is defined as the electrical resistance between two points of a conductor when a constant potential difference of one volt (V), applied to these points, produces a current of one ampere (A).
Resistance is related to voltage and current through Ohm's law, which states that there is a proportional relationship between the three quantities in an electrical circuit.
