CBSE 2023 · Region 4 · Set 1 · Q25 · 2 marks
Obtain an expression for electrostatic potential energy of a system of three charges $\displaystyle \mathrm{q}, 2 \mathrm{q}$ and $\displaystyle -3 \mathrm{q}$ placed at the vertices of an equilateral triangle of side a.Two small conducting balls A and B of radius $\displaystyle \mathrm{r}_{1}$ and $\displaystyle \mathrm{r}_{2}$ have charges $\displaystyle \mathrm{q}_{1}$ and $\displaystyle \mathrm{q}_{2}$ respectively. They are connected by a wire. Obtain the expression for charges on A and B , in equilibrium.
Obtain an expression for electrostatic potential energy of a system of three charges $\displaystyle \mathrm{q}, 2 \mathrm{q}$ and $\displaystyle -3 \mathrm{q}$ placed at the vertices of an equilateral triangle of side a.
Two small conducting balls A and B of radius $\displaystyle \mathrm{r}_{1}$ and $\displaystyle \mathrm{r}_{2}$ have charges $\displaystyle \mathrm{q}_{1}$ and $\displaystyle \mathrm{q}_{2}$ respectively. They are connected by a wire. Obtain the expression for charges on A and B , in equilibrium.
Marking-scheme solution
(a) 
OR
a similar diagram with different order of charges
\[U=\frac{1}{4 \pi \epsilon_{0}} \cdot \frac{\mathrm{q}_{1} \mathrm{q}_{2}}{\mathrm{r}}
\] \(\displaystyle U=\frac{1}{4 \pi \epsilon_{0}}\left[\frac{2 \mathrm{q}^{2}}{a}-\frac{6 \mathrm{q}^{2}}{a}-\frac{3 \mathrm{q}^{2}}{a}\right] U=\frac{1}{4 \pi \epsilon_{0}} \frac{\left(-7 \mathrm{q}^{2}\right)}{a}\)OR
Electrostatic Potential and CapacitancePotential Energy of a System of ChargesApplyvery_short_answermedium
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CBSE Class 12 Physics past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.