Definition of Resistance
The property of the substance to resist the flow of electric current through it is known as resistance. The unit of resistance is Ohm. The conductors have free electrons moving randomly inside the metal, and on the application of voltage, the electrons start moving from the lower potential point to the higher potential point.
During the drifting of the electrons, the collision between the electrons and atom and molecule of the conductor takes place, and this collision impedes the path of flow of electrons. This impediment of the flow of electrons caused by the collision of electrons with atoms and molecules creates a hindrance. The electrical hindrance in the path of current flow is the electrical resistance.
When we apply the voltage in a circuit, the current flows through the resistance. Let the voltage across resistance be V, and the current flowing in the circuit is I. The voltage across the resistance is proportional to the flow of electric current. According to Ohms’ Law,
V ∝ I
V = RI
R = V/I Where,
V – Voltage
I – Current
R – Resistance of the substance
Hence, we can define resistance as the ratio of the applied voltage to the current through the substance.
R = V/I
Unit of Resistance
Applying one volt of potential difference across the resistance causes a 1-ampere current to flow through it; then, the resistance is equal to 1 Ω. The unit of resistance is volt per ampere or ohm, named after George Ohm. The symbol of Ohm is omega (Ω ). The SI unit of the resistance is Ohm(Ω)
R = V/I ( Ohm’s Law)
= 1 Volt/ 1 ampere
R =1 Ohm (Ω)
Different Units of Resistance
The larger units of resistance are Kilo-Ohm, Mega-Ohm, and Giga-Ohm. The smaller resistance units are milli Ohm, Micro Ohm, and nano Ohm.
The relationship between different resistance units is given below. The different units for resistance are;
| Resistance unit | Value in Ohm(Ω) |
| 1 Giga Ohm (GΩ) | 109 Ω |
| 1 Mega Ohm (M Ω) | 106 Ω |
| 1 Kilo Ohm (K Ω ) | 103 Ω |
| 1 Milli Ohm (m Ω) | 10-3 Ω |
| 1 Micro Ohm (μΩ ) | 10-6 Ω |
| 1 Nano Ohm (nΩ ) | 10-9 Ω |
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