what does the value of resistance indicates ? On what basis the value of resistance is assigned to a resistor ? How manufacturers are assigning value to the resistor? Is it on the basis of how much amount of current to be flown in a circuit?

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  • \$\begingroup\$ Look up Ohm's Law for one thing. Resistance isn't "assigned". It is intrinsic to all materials. \$\endgroup\$ – DerStrom8 Feb 14 '18 at 12:54
  • \$\begingroup\$ Resistance is a property which exists in all materials. It depends on resistivity, length and cross-sectional area of the material. In Wikipedia, search for resistivity and resistance. \$\endgroup\$ – Mitu Raj Feb 14 '18 at 13:07

By resistance you are actually talking about the Ohmic Resistance of something.

This value was first described by Georg Simon Ohm in a scientific paper called The Galvanic Circuit Investigated Mathematically.

In that paper Georg defined Resistance \$R\$ as a value that relates the amount of current \$I\$ that passes through the device or wire when a given voltage \$V\$ is applied across it.

That is:

\$R = V/I\$

Part of that paper was later established as Ohm's Law by James Clerk Maxwel

Since the value of resistance itself is defined by that very equation, it is clear that resistance dictates the current in a circuit for linear devices.

For non-linear devices like diodes, and more history, read this answer.

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  • \$\begingroup\$ ,we are determining the value of current in the circuit ,if and only if we know the value of resistance .the value of resistance indicates what?is it is designed on the basis that the amount of current to be flown in the circuit.how manufacturers are assigning a value to a resistor and on what basis they are assigning a value to a resistor? \$\endgroup\$ – Purushothaman Santhi Feb 17 '18 at 15:21
  • \$\begingroup\$ @PurushothamanSanthi resistors are made by sizing the materials then manufactured and measured and binned, and sometimes laser trimmed to match the particular design requirement. \$\endgroup\$ – Trevor_G Feb 17 '18 at 15:56
  • \$\begingroup\$ Here's another link to The Galvanic Circuit Investigated Mathematically, on Google Books. \$\endgroup\$ – Jonathon Reinhart Mar 10 '18 at 15:34

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