Chapter 6, Problem 53R

To determine

To calculate: the electrical energy provided for the appliance in $4\text{ h}$ .

Answer to Problem 53R

The electrical energy provided for the appliance is $\underset{\_}{\text{0}\text{.96 kWh}}$ .

Explanation of Solution

Given data:

Voltage difference across the appliance, $V=120\text{ V}$

Current, $I=2\text{ A}$

Time, $t=4\text{ h}$

Formula used:

• Electrical Power Equation:

  $P=IV$

Where $P$ is the power of a device in watts, $I$ is the current through the device in amperes, and $V$ is the voltage difference across the device in volts.

• Electrical Energy Equation:

  $E=Pt$

Where $E$ is the electrical energy provided by the power company in kilowatt-hours, $P$ is the power of an appliance in kilowatts, and $t$ is time in hours for which the energy is provided.

Calculation:

As per the problem,

  $\begin{array}{l}V=120\text{ V}\\ I=2\text{ A}\\ t=4\text{ h}\end{array}$

Substitute the values of current and voltage difference in the electrical power equation to get power:

  $\begin{array}{l}P=IV\\ P=(2\text{ A)(120 V)}\\ P=240\text{W}\\ P=0.24\text{kW}\end{array}$

Now, to find electrical energy provided for the appliance, substitute the values of power (calculated above) and time in the electrical energy equation:

  $\begin{array}{l}E=Pt\\ E=(0.24\text{ kW)(4 h)}\\ E=0.96\text{kWh}\end{array}$

Conclusion:

The electrical energy provided for the appliance is $\underset{\_}{\text{0}\text{.96 kWh}}$ .