Question

An infinitely long thin straight wire has uniform charge density of $\frac {1}{4} \times 10^{-2} cm^{-1}.$ What is the magnitude of electric field at a distance $20\, cm$ from the axis of the wire ?

• A. $1.12 \times 10^8 \,NC^{-1}$
• B. $4.5 \times 10^8 \,NC^{-1}$
• C. $2.25 \times 10^8 \,NC^{-1}$
• D. $9 \times 10^8 \,NC^{-1}$

Answer 1

Answer: (C)

We know that
$E=\frac{\lambda}{2 \pi \varepsilon_{0} r}$
$=\frac{1}{4} \times \frac{10^{-2}}{10^{-2}} \times 18 \times 10^{9} \times 5$
$=2.25 \times 10^{8} N / C$