Question 969: Electrostats & Capacitance

Question

Three charges, each of $+4 \mu \mathrm{C}$, are placed at the corners $A, B, C$ of a square $A B C D$ of side 1 m . What is the magnitude (in $\mathrm{NC}^{-1}$ ) of electric field at point $O$ towards point $D$ ?

Accepted Answer

$$\begin{aligned}
&E_A 	ext { cancels } E_C 	ext {. }\
&	ext { At } \begin{aligned}
E_B & =\frac{1}{4 \pi \varepsilon_0} \frac{q}{\left(\frac{d}{\sqrt{2}}ight)^2} \
& =\frac{1}{4 \pi \varepsilon_0} \frac{2 q}{d^2} \
& =\frac{9 	imes 10^9 	imes 2 	imes 4 	imes 10^{-6}}{1^2} \
& =72 	imes 10^4 \mathrm{~N} / \mathrm{C}, 	ext { towards } D \
& =72000 \mathrm{~N} / \mathrm{C}
\end{aligned}
\end{aligned}$$

Answer

66000

Answer

72000

Answer

51000

Answer

64000

Electrostats & Capacitance

Three charges, each of +4 \mu \mathrm{C}, are placed at the corners A, B, C of a square A B C D of side 1 m . What is the magnitude (in \mathrm{NC}^{-1} ) of electric field at point O towards point D ?

Choose the correct answer: