Answer
50
4.8 V
Work Step by Step
Use equation 21-6 to find the turns ratio.
$$\frac{N_S}{N_P}=\frac{V_S}{V_P}$$
$$=\frac{12000V}{240V}=50$$
If the transformer were reversed, the secondary and primary would switch roles. Instead of stepping up the initial voltage by a factor of 12000V/240V, the transformer would step down the voltage by the same factor.
$$V_{out}=(240V)\frac{240V}{12000V}=4.8V$$
