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# E = IVt

### E = IVt

We can calculate the energy transferred in a circuit by using the formula energy = current x voltage x time.

What is the golden rule of physics?

In what form does the energy in a circuit begin if the circuit contains a battery?

**True** or **false**? Chemical energy in the battery is transferred to kinetic energy in the circuit.

By what other name do we call the kinetic energy of the **electrons**?

Electrical current is created from a transfer of energy: It began as **chemical** **energy** stored in the battery and was transferred to **electrical** **energy**, which is a form of **kinetic** **energy**, as electrons move around the circuit.

If you want to work out how much energy is transferred, we need to know the **current**, the **voltage** and for **how long** the current is flowing around the circuit.

The formula to work out the energy transferred in a circuit is $E=I\times V\times t$.

$E$ is the energy measured in **joules (J),**

$I$ is the current measured in **amps (A),**

$V$ is potential difference measured in **volts (V),**

$t$ is time measured in **seconds (s).**

How much energy is transferred through a circuit in 2 seconds, if the current is 1 amp and the voltage is 4 volts?

A circuit is switched on for **4 seconds** with a current of **4 amps** and a voltage of **140 volts**. What is the energy transferred?

Remember that $E=I\times V\times t$and that $Q=I\times t$. Now, how can we change the formula for energy to be in terms of $Q$? Remember to simplify the final result.

We can calculate the energy in a circuit in two different ways, depending on what information we have.
If we have the **current**, **voltage** (or P.D.) and **time** we can use $E=I\times V\times t$.
If we have the **charge** and the **voltage**, we can use $E=Q\times V$.

How do we calculate the resistance in a circuit if we have the **current** and the **voltage**?

We can work out the **voltage**, **current** and **resistance**, using the $V=IR$ formula.

We can make $V$ the object of the formula by using it as it is.

$V=I\times R$

Now, make current $I$ the subject.

Now, make resistance $R$ the subject.