Energy and Voltage in Circuits

Energy Transfer in Circuits

Electrical energy is transferred into other forms of energy when an electric current passes through a component.
In a filament bulb, most of the electrical energy is transferred to heat energy, with a smaller amount transferred to light energy.
The electrical power of a device is the rate at which electrical energy is converted into other forms. It is measured in watts (W) or kilowatts (kW).

Voltage (also called potential difference) is the energy transferred per unit charge that passes through a component. It is measured in volts (V).
The higher the voltage, the more energy is transferred for each charge that flows.
Furthermore, the voltage between two points in a circuit is the work done (or energy transferred) per unit charge to move charge from one point to another.

Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points.
It can be summarised by the equation V = IR, where V is the voltage, I is the current, and R is the resistance.
Ohm’s law enables the calculation and prediction of behaviour in electrical circuits.

In a series circuit, the total voltage supplied is shared between the components. Therefore, the total voltage equals the sum of the voltages across each component.
Whereas, in a parallel circuit, all components are directly connected to the source of the voltage. Therefore, they all get the same voltage.
Components connected in series have the same current through them, but components in parallel have different currents through them.

Power in a circuit can be calculated using the formula P = IV, where P is power, I is current, and V is voltage.
Electrical devices are often labelled with their power rating. This enables one to calculate the current drawn from the supply when the device is running at full power.
Efficiency of an appliance can be expressed as useful power output divided by total power input. The more efficient an appliance is, the higher the proportion of the input power is usefully output and the less is wasted.

The cost of running electrical appliances can be calculated if the power, time used, and electricity tariff are known.
The amount of electrical energy consumed by an appliance can be calculated using the formula E = P x t, where E is energy, P is power, and t is time. Energy is usually measured in kilowatt-hours (kWh).