Question

One kilowatt hour is equal to

• A. \( 36 \times 10^6 \, J \)
• B. \( 0.36 \times 10^6 \, J \)
• C. \( 3.6 \times 10^{10} \, J \)
• D. \( 3.6 \times 10^6 \, J \)

Hint:

Kilowatt hour is a commonly used unit for measuring electrical energy consumption. Remember the conversion factors between kilowatts and watts, and hours and seconds, to convert it to Joules.

Answer 1

The Correct Option is D

Step 1: Understand the units of kilowatt hour.
Kilowatt hour (kWh) is a unit of energy. It is the energy consumed by a 1 kilowatt (kW) device operating for 1 hour. Step 2: Convert kilowatts to watts. \[ 1 \, \text{kilowatt (kW)} = 1000 \, \text{watts (W)} \] Step 3: Convert hours to seconds. \[ 1 \, \text{hour (h)} = 60 \, \text{minutes (min)} = 60 \times 60 \, \text{seconds (s)} = 3600 \, \text{s} \] Step 4: Express kilowatt hour in terms of watt-seconds (Joules). \[ 1 \, \text{kWh} = 1 \, \text{kW} \times 1 \, \text{h} \] \[ 1 \, \text{kWh} = (1000 \, \text{W}) \times (3600 \, \text{s}) \] \[ 1 \, \text{kWh} = 3,600,000 \, \text{W} \cdot \text{s} \] Step 5: Recall the definition of a Joule. \[ 1 \, \text{Joule (J)} = 1 \, \text{Watt} \cdot \text{second (W s)} \] Step 6: Convert kilowatt hour to Joules. \[ 1 \, \text{kWh} = 3,600,000 \, \text{J} \] Step 7: Express the result in scientific notation. \[ 1 \, \text{kWh} = 3.6 \times 10^6 \, \text{J} \] One kilowatt hour is equal to \( 3.6 \times 10^6 \, J \).