Question

the resistance of the copper wire of radius r is Rfind out the resistance of other copper wire of same length but of 2r radius. show me the steps

Answer 1

R depends on (resistivity ×length of wire )÷ area of cross section of the wire
so for both cases resistivity is same (same material copper ) and length is also same
hence if radius is becoming 2r that mean means area become 4times {Pie×r²}
so resistance decreases 4 times
R`=R/4