Determining the electric power using electric energy and time is fundamental in understanding how electrical devices consume energy. The relationship between these quantities is expressed through a specific formula, which we will explore with practical examples.
The Formula: \( P = \dfrac{E}{t} \)
Where:
- \( P \) is the electric power (measured in watts, W)
- \( E \) is the electric energy (measured in joules, J)
- \( t \) is the time (measured in seconds, s)
Example 1: Power Consumption of a Light Bulb
Question: A light bulb uses 1800 joules of energy over 60 seconds. What is the power consumption of the light bulb?
Calculation:
Given:
- \( E = 1800 \) J
- \( t = 60 \) s
Using the formula:
\[ P = \dfrac{E}{t} = \dfrac{1800}{60} = 30 \, \text{W} \]
Result: The power consumption of the light bulb is 30 watts.
Example 2: Power of a Microwave Oven
Question: A microwave oven uses 54,000 joules of energy in 90 seconds. What is the power rating of the microwave oven?
Calculation:
Given:
- \( E = 54,000 \) J
- \( t = 90 \) s
Using the formula:
\[ P = \dfrac{E}{t} = \dfrac{54,000}{90} = 600 \, \text{W} \]
Result: The power rating of the microwave oven is 600 watts.
Example 3: Power Output of a Battery Charger
Question: A battery charger delivers 10,800 joules of energy in 3600 seconds. What is the power output of the battery charger?
Calculation:
Given:
- \( E = 10,800 \) J
- \( t = 3600 \) s
Using the formula:
\[ P = \dfrac{E}{t} = \dfrac{10,800}{3600} = 3 \, \text{W} \]
Result: The power output of the battery charger is 3 watts.
