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6.3 What is Resistor?

Description:


  • Resistor, restricts or limits the flow of electrons in a circuit.
  • As discussed in the previous post, materials fall into two basic categories such as conductors and insulators. 
  • Conductors such as metals let electricity flow through them; insulator such as plastic and wood generally do not. 
  • But, any substance will conduct electricity if you put big enough voltage across it; even air which  is normally an insulator suddenly becomes a conductor when a powerful voltage builds up in the clouds and what makes lightning.
  • Rather than talking about conductors and insulators, it's better to talk about resistance, (the ease with which something will let electricity flow through it)
  • A conductor has low resistance, while an insulator has much higher resistance.
  • Devices called resistors, let us introduce precisely controlled amounts of resistance into electric circuits. 
  • Resistor is a passive electrical component with two terminals that are used for either limiting or reducing the flow of current in any particular portion of the electric circuit.
  • It is also used to transform current signal into a voltage signal and vice versa.

Made up of: 

  • Copper wires which are coiled around a ceramic rod.
  • And the outer part is coated with an insulating paint.


  • A resistor doesn't have any fixed "positive or negative" terminal.
  • When a current (I) flows through a circuit, the terminal through which the current enters into the resistor will be considered as positive terminal and the other one will be considered as the negative terminal.
  • Otherwise, a resistor alone doesn't have any fixed positive or negative terminal.

SI Unit of Resistance is Ohm

  • An Ohm is the resistance that occurs when a current of one Ampere (A) passes through resistor with a one volt (V) drop across its terminals.

Symbol of Resister:

  • Both are symbols of a fixed resistor.
  • The first symbol belongs to ANSI standard and the second belongs to IEC standard. 
  • R1 and R2 are one kiloohm and 47 Kiloohm Resistors respectively.
  • A kiloohm (kΩ) = 103 Ohms i.e., One kiloohm is equal to 1,000 ohms.



Read the next post: 6.4 Ohm's Law

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