Electricity is the movement of electrons in a current.
Current is the flow rate of charges through a wire. Current is measured in amperes, and is sometimes called amperage, though engineers frown on this term.
Voltage is a measure of power. Voltage in itself is not entirely dangerous. It is amperage that kills people.
A watt is a measure of power x current. Learn more about power terms from the glossary
Alternating current (AC) is the kind of electrical current commonly used to power all your household items, available from plug outlets in your wall. Alternating current is the most efficient transmission of energy. Its most common form is a sine wave, meaning a very "smooth" wave. Other forms of alternating current are triangular and square waves. The magnitude of alternating current varies in a cyclical form.
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Direct current, on the other hand is a current whose polarity remains constant (with no variation). Direct current is most commonly available in batteries.
Why is AC more commonly used?
It is much better suited to transmission over long distances. With direct current, there is a potential loss of power relational to the distance it travels.