Question

When building an electronic toy, a buzzer requires 30 mA (.03 amps) of current. If the voltage from the batteries for the toy add up to 12 volts, what sized resister must be used to ensure the buzzer receives the necessary 30 mA of current. Enter the numerical value rounded to the nearest whole number. For example if you calculate 327.45 ohms, enter 327.

Answer 1

Ohm's law states that the resistance, current and voltage are related from the equation:

$R=\frac{V}{I}$

In this case we know the voltage is 12 V and the current is 0.3 A, plugging these values we have:

$\begin{gathered} R=\frac{12}{0.3} \\ R=400 \end{gathered}$

Therefore, the resitsance need is 400 Ohms.