Question

a siren operates at 24 volts and draws 30ma of current. what is the sirens resistance? 0.8ω 24ω 720ω 800ω

Explanation:

Step1: Convertir la corriente a amperios

$$I = 30\mathrm{mA}=30\times10^{-3}\mathrm{A} = 0.03\mathrm{A}$$

Step2: Aplicar la ley de Ohm ($V = I\times R$, despejar $R$)

$$R=\frac{V}{I}$$
Sustituir $V = 24\mathrm{V}$ y $I = 0.03\mathrm{A}$:
$$R=\frac{24}{0.03}$$
$$R = 800\Omega$$

Answer:

800 Ω