W obliczeniach korzystamy ze wzoru na napięcie z definicji:

$\text{U}=\frac{\text{W}}{\text{q}}$  

Obliczamy kolejne wiersze:

• wiersz 1.

${\text{U}}_1=\frac{{\text{W}}_1}{{\text{q}}_1}=\frac{100\text{J}}{20\text{C}}$  

${\text{U}}_1=5\text{V}$  

• wiersz 2.

${\text{U}}_2=\frac{{\text{W}}_2}{{\text{q}}_2}\text{/}\cdot {\text{q}}_2$  

${\text{U}}_2\cdot {\text{q}}_2=\frac{{\text{W}}_2\cdot \sout{{\text{q}}_2}}{\sout{{\text{q}}_2}}$  

${\text{U}}_2\cdot {\text{q}}_2={\text{W}}_2{\text{/: U}}_2$  

$\frac{\sout{{\text{U}}_2}\cdot {\text{q}}_2}{\sout{{\text{U}}_2}}=\frac{{\text{W}}_2}{{\text{U}}_2}$  

${\text{q}}_2=\frac{{\text{W}}_2}{{\text{U}}_2}=\frac{200\text{J}}{25\text{V}}$  

${\text{q}}_2=8\text{C}$  

• wiersz 3.

${\text{W}}_3={\text{U}}_3\cdot {\text{q}}_3=20\text{V}\cdot 15\text{C}$  

${\text{W}}_3=300\text{J}$  

Uzupełniamy tabelę:

q [C]	U [V]	W [J]
20	5	100
8	25	200
15	20	300