Thu April 19, 2012 By:

When the conducting material itself provides certain amount of resistance,why do we need a separate resistor?

Expert Reply
Thu April 19, 2012
There is always some resistance in every circuit.
• A circuit is always made up of some wire, so there will be some resistance there.
• Even the battery has parts that offer resistance to the flow ofelectrons.
• The only circuits that come near to zero resistance aresuperconductors.
• This resistance that is from the parts of the circuit itself (especiallythe battery) is called internal resistance.
The most common reason for separate resistance is that we need to be able to adjust the current flowing through aparticular part of the circuit.
• If voltage is constant, then we can change the resistor to change the current.I =VRIf “V” is constant and we change “R”, “I” will be different.
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