Figure 11 (a) Electricity supplied to homes has a frequency of ☐ A 0.02 Hz ☐ B 20 Hz ☐ C 50 Hz ☐ D 500 Hz (b) Explain why the National Grid uses high voltages with small currents to transfer electricity from power stations - Edexcel - GCSE Physics - Question 5 - 2023 - Paper 2

The National Grid uses high voltages for electricity transmission in order to minimize energy loss over long distances. Higher voltage enables the use of lower currents, which reduces the energy lost as heat due to the resistance in the wires. This method is efficient for transporting large amounts of electrical energy from power stations to consumers.

To calculate the power in the primary coil, we use the formula:

$P = V × I$

where P is power, V is voltage, and I is current. To provide a specific numerical answer, the values for voltage and current must be known. Assuming some values: If V = 200 V and I = 0.1 A:

$P = 200 ext{ V} × 0.1 ext{ A} = 20 ext{ W}$

Thus, power in the primary coil = 20 W.

To evaluate the ratio of secondary voltage to primary voltage for the transformer, we must know the number of turns in the primary and secondary coils. Assuming the turns ratio is represented as:

rac{V_s}{V_p} = rac{N_s}{N_p}

where $V_s$ is the secondary voltage, $V_p$ is the primary voltage, $N_s$ is the number of turns in the secondary coil, and $N_p$ is the number of turns in the primary coil. Without specific values, we cannot compute the exact ratio.