Question

Q11. How does the resistance of wire vary with its area of cross-section? When a 12V battery is
connected across an unknown resistor, there is a current of 2.5mA in the circuit. Find the value of
resistance of resistor.
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Answer 1

Answer:

The resistance of a wire is inversely proportional to the area of cross-section as ,more the area, less are the electron electron collisions and more area for the electrons to travel.

Now, given: V=12 V

I (current) = 2.5mA = 2.5×10^-3 A= 0.0025 A

Let the unknown resistance be R,

By Ohm's law,

V=IR

R=V/I =12/0.0025

R=4800 Ohms = 4.8 kOhms