Question 806: Electrostats & Capacitance

Question

$A$ sphere ' $A$ ' of radius ' $R$ ' has a charge ' $Q$ ' on it. The field at point B outside the sphere is ' $E$ '. Now another sphere of radius ' $2 R$ ' having a charge ' $-2 Q$ ' is placed at B. The total field at the point midway between A and B due to both the spheres is

Accepted Answer

The field at point ' $B$ ' due to sphere of charge ' $Q$ ' will be,
$$\mathrm{E}=\frac{\mathrm{KQ}}{\mathrm{r}^2}$$
Electric field at mid-way between points '$A$ ' and ' $B$ ' will be,
$$\begin{aligned}
E^{\prime} & =\frac{K Q}{\left(\frac{r}{2}ight)^2}+\frac{K(2 Q)}{\left(\frac{r}{2}ight)^2} \
& =\frac{4 K Q}{r^2}+\frac{8 K Q}{r^2} \
E^{\prime} & =\frac{12 K Q}{r^2}=12 E
\end{aligned}$$

Answer

E

Answer

3E

Answer

12E

Answer

15E

Electrostats & Capacitance

A sphere ' A ' of radius ' R ' has a charge ' Q ' on it. The field at point B outside the sphere is ' E '. Now another sphere of radius ' 2 R ' having a charge ' -2 Q ' is placed at B. The total field at the point midway between A and B due to both the spheres is

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