A certain household has consumed 250 units of energy during a month. How much energy is this in joules ?

Explanation

To convert the energy consumed in kilowatt-hours to joules, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the given energy consumption**:
The household has consumed 250 units of energy. In the context of electrical energy, 1 unit is equivalent to 1 kilowatt-hour (kWh). Therefore, we have:
\[ \text{Energy consumed} = 250 \text{ kWh} \]

2. **Convert kilowatt-hours to watt-hours**:
Since 1 kilowatt (kW) is equal to 1000 watts (W), we convert kilowatt-hours to watt-hours:
\[ 250 \text{ kWh} = 250 \times 1000 \text{ Wh} = 250000 \text{ Wh} \]

3. **Convert watt-hours to joules**:
We know that 1 watt is equal to 1 joule per second. To convert watt-hours to joules, we need to account for the time in seconds. Since 1 hour is equal to 3600 seconds, we have:
\[ 250000 \text{ Wh} = 250000 \text{ W} \times 3600 \text{ s} \]

4. **Calculate the total energy in joules**:
Now we can perform the multiplication:
\[ 250000 \text{ W} \times 3600 \text{ s} = 900000000 \text{ J} \]
This can also be expressed in scientific notation:
\[ 900000000 \text{ J} = 9 \times 10^8 \text{ J} \]

5. **Final Answer**:
Therefore, the energy consumed in joules is:
\[ \text{Energy in joules} = 9 \times 10^8 \text{ J} \]