Chapter 22.2, Problem 38SSC

To determine

The reason that an electric range and an electric hot-water heater would be connected to a $240\text{-V}$ circuit rather than to a $120\text{-V}$ circuit.

Answer to Problem 38SSC

To have less thermal energy loss,

Explanation of Solution

Introduction:

The electric power $\left(P\right)$ is given by,

  $P=IV$

Where, I is the current and V is the potential difference.

And, the thermal energy $\left(E\right)$ during time $t$ is given by,

  $\begin{array}{c}E=Pt\\ =\frac{I^{2}t}{R}\end{array}$

Where,

  $\begin{array}{l}P=\text{Power dissipated}\\ I=\text{ Current}\\ R=\text{Resistance}\end{array}$

Considering the above mentioned formula for the power, for the same power if the voltage is more, then the current will be less.

Then, considering the formula for the thermal energy loss, if the current through the circuit is less, the thermal energy loss will also be less.

Conclusion:

Hence, to have the less loss due to thermal energy, an electric range and an electric hot-water heater would be connected to a $240\text{-V}$ circuit rather than to a $120\text{-V}$ circuit.