A current of 2A passes through a wire of resistance 4Ω for 3 minutes. Calculate the energy lost.

Analyze the question: A current flows through a resistor for a given time. The electrical energy converted to heat (energy lost) is required.

Concept: Energy dissipated in a resistor is given by Joule's law:

W = I²Rt

where I is current (A), R is resistance (Ω), and t is time in seconds.

Solution:

• I = 2 A
• R = 4 Ω
• t = 3 minutes = 3 × 60 = 180 s

W = I²Rt W = (2)² × 4 × 180 W = 4 × 4 × 180 W = 16 × 180 W = 2880 J

Answer: The energy lost is 2880 J, which matches option C.

Tip: The most common mistake is forgetting to convert minutes to seconds. If you used t = 3, you would get 48 J (option D), which is a trap. Always convert time to seconds before using joule-based formulas. Also remember the three forms of the heat formula: W = I²Rt = VIt = V²t/R.