A Level Physics Practice Exam

To determine the energy equivalent of 1 kilowatt-hour (kWh), we start with the definition of a kilowatt-hour: it is the energy consumed when a power of one kilowatt (1 kW) is used for one hour. The relationship between power, energy, and time can be expressed as:

Energy (in joules) = Power (in watts) × Time (in seconds)

1 kilowatt is equal to 1,000 watts, so we can express 1 kWh as follows:

1 kWh = 1,000 watts × 1 hour

Now, we need to convert hours into seconds. There are 3600 seconds in an hour (60 seconds per minute × 60 minutes per hour). Therefore:

1 kWh = 1,000 watts × 3,600 seconds

Now, multiplying these together gives:

1 kWh = 1,000 × 3,600 = 3,600,000 joules

This can be expressed in scientific notation as:

1 kWh = 3.6 × 10^6 J

Thus, the energy equivalent of 1 kWh is indeed 3.6 × 10^6 J. This clearly supports the chosen answer