The primary side of a transformer is connected to 230V, 50Hz...

The voltages associated with the primary and the secondary side of the transformer are related to the turn ratio as follows:

$\dfrac{{V}_{1}}{{V}_{2}} = \dfrac{{N}_{1}}{{N}_{2}} . . . \left(1\right)$

From equation (1), it follows that

$\dfrac{230}{{V}_{2}} = \dfrac{10}{1}$

${V}_{2} = 23V$

Hence, the power consumed can be calculated as follows

$\begin{cases}P & = & {V}_{2}^{2}R \\ & = & \dfrac{23 \times 23}{46} \\ & = & 11 . 5W\end{cases}$