Power is a measure of the rate of energy transfer and relates to the current and voltage for an electrical circuit.

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Electrical energy is easy to move from place to place, using wire or cables. However, electrical energy must be changed into other forms of energy before we can use it.

The rate at which energy is transferred (or changed) is called Power – how much energy is used per second.

\[Power = \frac{{Energy}}{{time}}\]

\[P = \frac{E}{t}\]

The symbol for **power** is \(P\), it is measured in **Watts** (\(W\)).

The symbol for **energy** is \(E\), it is measured in **Joules** (\(J\)).

The symbol for **time** is \(t\), it is measured in **seconds** (\(s\)).

The electrical energy transferred each second is found by multiplying voltage by current.

\[Power = Voltage \times current\]

\[P = V \times I\]

The symbol for **power** is \(P\), it is measured in **Watts** (\(W\)).

The symbol for **voltage** is \(V\), it is measured in **Volts** (\(V\)).

The symbol for **current** is \(I\), it is measured in **Amperes** (\(A\)).

Sometimes we don't know the current or voltage, so \(P = IV\) cannot be used to calculate the power. In these situations, we use Ohms Law to find an alternative power equation where more of the information is available.

\[P = \frac{{{V^2}}}{R}\]

The symbol for **power** is \(P\), it is measured in **Watts** (\(W\)).

The symbol for **voltage** is \(V\), it is measured in **Volts** (\(V\)).

The symbol for **resistance** is \(R\), it is measured in **Ohms** \((Ω)\).

\[Power = curren{t^2} \times resistance\]

\[P = {I^2}R\]

The symbol for **power** is \(P\), it is measured in **Watts** (\(W\)).

The symbol for **current** is \(I\), it is measured in **Amperes** (\(A\)).

The symbol for **resistance** is \(R\), it is measured in **Ohms** (\(Ω\)).