An electric heater is rated 1500W. How much energy does it use in 10 hours ?

Options

A. 12 units
B. 20 units
C. 15 units
D. 10 units

Explanation

To solve the problem of how much energy an electric heater rated at 1500W uses in 10 hours, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Power Rating**:
The power rating of the electric heater is given as 1500 watts (W).

2. **Convert Time to Seconds**:
Since energy is typically calculated in joules (J) and power in watts (W), we need to convert the time from hours to seconds.
\[ \text{Time} = 10 \text{ hours} = 10 \times 60 \text{ minutes/hour} \times 60 \text{ seconds/minute} = 36,000 \text{ seconds} \]

3. **Use the Energy Formula**:
The relationship between energy (E), power (P), and time (t) is given by the formula:
\[ E = P \times t \]
Here, \(E\) is the energy in joules, \(P\) is the power in watts, and \(t\) is the time in seconds.

4. **Substitute the Values**:
Now, substitute the values of power and time into the formula:
\[ E = 1500 \text{ W} \times 36,000 \text{ s} \]

5. **Calculate the Energy**:
Performing the multiplication:
\[ E = 1500 \times 36,000 = 54,000,000 \text{ J} = 5.4 \times 10^7 \text{ J} \]

6. **Convert to Kilowatt-Hours (Optional)**:
To express the energy in kilowatt-hours (kWh), we can convert joules to kilowatt-hours using the conversion factor:
\[ 1 \text{ kWh} = 3.6 \times 10^6 \text{ J} \]
Thus, we can calculate:
\[ E = \frac{54,000,000 \text{ J}}{3.6 \times 10^6 \text{ J/kWh}} = 15 \text{ kWh} \]

### Final Answer:
The electric heater uses **54,000,000 joules** (or **15 kilowatt-hours**) of energy in 10 hours.

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