Question

If a “75-W” bulb (see Problem 25.35) is connected across a 220-V potential difference (as is used in Europe), how much power does it dissipate? Ignore the temperature dependence of the bulb’s resistance.

Short answer

The power dissipated across 220-V is 252 W.

Step-by-step solution

Concept of Electric Power.

The electrical energy flowing through or transferred by an electric circuit in unit time is the definition of electric power. It is nothing by the rate at which the electrical energy flows through the circuit.

$P=\frac{E}{t}J/s$

(b) Determination of the power dissipation.

The connection of the bulb is across a 120-V potential difference.

The expression of power is,

$P=\frac{V^2}{R}$

Solve for R and 75-W bulb,

$$\begin{gathered} R=\frac{V^2}{P} \\ =\frac{{\left(120V\right)}^2}{\left(75W\right)} \\ =192\Omega \end{gathered}$$

The connection of the bulb is across a 220-V potential difference.

The expression of power is,

$$\begin{gathered} \mathrm{P}=\frac{{\mathrm{V}}^2}{\mathrm{R}} \\ \mathrm{P}=\frac{{(220\mathrm{V})}^2}{\left(192\mathrm{\Omega }\right)} \\ =252\mathrm{W} \\ \mathrm{Thus},\mathrm{the}\mathrm{power}\mathrm{dissipated}\mathrm{is}252\mathrm{W}. \end{gathered}$$