An electric charge of 10nC is placed at the point  $\mathrm{O}\left(4\mathrm{m},7\mathrm{m},2\mathrm{m}\right)$ .At the point $\mathrm{P}\left(1\mathrm{m},3\mathrm{m},2\mathrm{m}\right)$

$\overrightarrow{r}=\left|{\overrightarrow{r}}_2-{\overrightarrow{r}}_1\right|=\left|\left(1-4\right)\widehat{i}+\left(3-7\right)\widehat{j}+\left(2-2\right)\widehat{k}\right|=5m$

$\Rightarrow \hat{\mathrm{r}}=\frac{-3\hat{\mathrm{i}}-4\hat{\mathrm{j}}}{5}$

$V_P=\frac{kq}{r}=\frac{9\times {10}^9\times 10\times {10}^{-9}}{5}=18volt$

$\overrightarrow{{\mathrm{E}}_{\mathrm{P}}}=\frac{\mathrm{kq}}{{\mathrm{r}}^2}\hat{\mathrm{r}}=\frac{9\times {10}^9\times 10\times {10}^{-9}}{5^2}\hat{\mathrm{r}}=3.6 \hat{\mathrm{r}} \mathrm{N}/\mathrm{C}$, So the electric field has no z-component.