The National Grid - Ireland's Transmission System The national grid system supplies electricity to customers - Leaving Cert Physics - Question 11 - 2013

High voltages are used to minimize power losses due to resistance in the transmission lines. The formula for power loss in the lines can be expressed as:

$P_{loss} = I^2 R$

where $I$ is the current and $R$ is the resistance. Higher voltage results in lower current for the same power transfer, thereby reducing losses.

The power supplied to domestic customers is at lower voltages for safety reasons and to ensure compatibility with household appliances, which typically operate at a lower voltage range.

Two renewable energy sources are:

• Wind
• Solar

Two non-renewable sources are:

• Coal
• Natural gas.

The difference between alternating current (a.c.) and direct current (d.c.) is as follows:

• A.C. varies in direction and magnitude, changing periodically, whereas D.C. flows in one direction only at a constant voltage.

The device used to convert high voltages to lower voltages is called a transformer.

The principle function of a transformer is to change the voltage level between circuits, either stepping it up or stepping it down according to the requirements of transmission and distribution.

One unit of electrical energy commonly used in this context is the kilowatt-hour (kWh).