The power plant generates a voltage of 4 875 V - NSC Technical Sciences - Question 9 - 2024 - Paper 1

Structures B, C, and D contain step-down transformers. These transformers are necessary to decrease the high voltage from the transmission lines to a safer, lower voltage suitable for residential consumption. This ensures that the voltage entering homes is manageable and safe for use.

We can use the transformer equation for this calculation. The relationship between the voltages and the number of turns in the coils of a transformer is given by:

$\frac{V_s}{V_p} = \frac{N_s}{N_p}$

Where:

• $V_s$ = secondary voltage
• $V_p$ = primary voltage = 6200 V
• $N_s$ = secondary turns = 4900
• $N_p$ = primary turns = 9000

Plugging in the values: $\frac{V_s}{6200} = \frac{4900}{9000}$

To find $V_s$, rearranging gives: $V_s = 6200 \times \frac{4900}{9000} = 3375.56 \text { V}$.

We can use Ohm's law to calculate the electric power:

$P = \frac{V^2}{R}$

Where:

• $P$ = power
• $V$ = voltage = 6200 V (the voltage at structure A)
• $R$ = resistance = 560 Ω

Thus, substituting the values into the formula gives:

$P = \frac{6200^2}{560} = 6864.29 \text{ W}$