Instantaneous power from energy and time: If 300 J of electrical energy are consumed uniformly in 15 s, what is the average power during that interval?

Introduction / Context:
Power quantifies the rate at which energy is used. When total energy over a time interval is known, average power is computed by dividing energy by time. This is fundamental in both electrical and mechanical systems.

Given Data / Assumptions:

• Total energy E = 300 J.
• Time interval t = 15 s.
• Assume uniform consumption to interpret as average power over the period.

Concept / Approach:

Use the definition P = E / t. Joule per second equals watt (1 J/s = 1 W). Ensure consistent SI units before dividing.

Step-by-Step Solution:

Verification / Alternative check:

Check units: joules divided by seconds is watts. 20 W over 15 s gives 300 J, confirming the calculation.

Why Other Options Are Wrong:

2 W and 0.2 W are too small by factors of 10 or 100. 200 W and 2,000 W are too large by factors of 10 or 100.

Common Pitfalls:

Converting to Wh unnecessarily (introduces rounding); mixing seconds and minutes; misplacing the decimal when dividing.

Final Answer:

20 W