The capacitance of a capacitor made by a thin metal foil is `2muF`. If the foil is filled with paperr of thickness 0.15 mm, dielectric constant of paper is 2.5 and width of the paper is 400 mm. what is the length of foil?

Options

A. 8.5 m
B. 13 m
C. 3.4 m
D. 34 m

Answer

D

Explanation

The capacitance, `C=(KA epsi_(0))/(d)`
`=(Kepsi_(0)(lxxb))/(d)" "(because A=lxxb)`
in this case, `C=2xx10^(-6)F,K=2.5`,
b=400mm=0.4m
`d=0.15mm=0.15xx10^(-3)=15xx10^(-5)m`
`therefore 2xx10^(-6)=(2.5xx8.85xx10^(-12)xxlxx0.4)/(15xx10^(-5))`
`therefore 2=(8.85lxx10^(-1))/(15)`
`therefore l=(30)/(8.85xx10^(-1))=34m`