Answer:
resistance R ≈ 0.26 ohms
Step-by-step explanation:
let the resistance be R and the radius r
given R varies inversely as r² , then the equation relating them is
R = [tex]\frac{k}{r^2}[/tex] ← k is the constant of variation
To find k, substitute R= 0.8 and r = 0.4 into the equation
0.8 = [tex]\frac{k}{0.4^2}[/tex] = [tex]\frac{k}{0.16}[/tex] ( multiply both sides by 0.16 )
0.128 = k
R = [tex]\frac{0.128}{r^2}[/tex] ← equation of variation
When r = 0.7 cm , then
R = [tex]\frac{0.128}{0.7^2}[/tex] = [tex]\frac{0.128}{0.49}[/tex] ≈ 0.26 ohms ( to the nearest hundredth )