Resistance | you need to know absolutely - Elucidate Techno

Some Definitions

• The degree to which a substance or device opposes the passage of an electric current, causing energy dissipation. (Source 1)

• The degree to which a substance prevents the flow of electric current through it. (Source 2) 

• The flow of charge through any material encounters an opposing force similar in many respects to mechanical friction. This opposition, due to the collisions between electrons and between electrons and other atoms in the material, which converts electrical energy into another form of energy such as heat is called the resistance of the material. (Source 3)

Resistance

Resistance - Elucidate Techno

Resistance is simply a barrier to the path of electron flow. It's something like speed breaker in the highway. Resistance reduces the flow of electricity or current. 

Classification 

There are basically two types of resistance

1. Internal Resistance
2. External Resistance

Internal Resistance

This is the characteristics of the material. When electric current flow through the material, it feels a resistance due to the properties of the material.

Materials Based On Internal Resistance

Depending on the internal resistance of the materials, they are divided into three categories.

• Conductor

This type of material has low resistance. So, the current can easily move through this material.Example: Metal.

• Insulator

This type of material has high resistance. So, the current can hardly move through this material.Example: Wood.

• Semiconductor

The resistance of this material between insulator and conductor. This is the most popular material in the field of electronics. Example: Copper.

External Resistance

The resistance that is attached to the electronic circuit manually to control or reduce the overflow electricity, is called External resistance.

Resistor

The component that is used to get external resistance, is called a resistor. 

Different kinds of resistors are available in the local markets. For example, 100 ohms resistor, 200 ohms resistor, 1k ohms resistor, etc.

Factors Of Internal Resistance

Different factors are related to the internal resistance of the material

• Resistivity
• Length
• Cross-sectional area
• Temperature

Resistivity

Resistivity depends on the material of the conductor. 
Suppose, the material of the wood has more resistivity than the material of the metal. It depends on the molecular structures of that material to determine resistivity.

Length

The increment of length of a conductor, increases the resistance of that conductor.
For example, 5m long metal has a lower resistance than 10m long same metal.

Cross-sectional Area

The smaller the cross-sectional area, the more the resistance.
For example, A metal with 2-meter sq cross-sectional has greater resistance than the same metal with 4-meter sq cross-sectional area.

Temperature

The higher the temperature of a conductor, the more the resistance.

Example

The resistance of metal at room temperature is lower than at 100-degree centigrade. 

HOW TO MEASURE RESISTANCE WITH MULTIMETER