- Power represents the energy consumed by the load.
- Energy the amount of electricity consumed or produced during a given period of time.
There are devices that can convert current from one format to another, or from a higher voltage curent to a lower voltage current and vice versa are universally referred to as “transformers.” Any time voltage or current type is transformed, there will always be some sort of energy loss, even if very small.
- A transformer that converts a higher voltage current to a lower voltage current is called a “step down” transformer, and can work by either converting high voltage low current loads to low voltage high current loads, or by adding resistance between two circuits to limit the voltage output, resulting in lower power being received on the output side.
- A transformer that converts to a higher voltage is called a “step up” transformer, and works by converting low voltage but high currents into high voltage but low currents. A step up transformer does not add additional electrical power to the circuit, it only increases overall voltage.
- A transformer that convers a current from DC to AC is called an inverter, and physically induces an alternating current on the output side. Inverters typically consume electrical power for the conversion process, and thus are less energy efficient than other forms of transformers.
- A transformer that convers a current from an AC to DC can be called a "battery charger" (for charging batteries) or a "power supply" (for direct powering of a radio, etc.), depending on how the conversion process works.
Direct Current (DC)
The main characteristics of a Direct Current – or DC – is that the electrons within the current always flow in the same direction, from the side with a deficit to the side with a surplus. This is the kind of current supplied via the chemical effect by batteries, or via the photovoltaic effect by solar panels. The terminals are marked + and – to show the polarity of the circuit or generator. The voltage and current are constant in time.