Cold filaments cause surge current four times the steady state

Steps:

• Steady-state power per lamp is 60W, so total power for eight lamps is 8 × 60W = 480W.
• Steady-state current is total power divided by voltage: 480W / 240V = 2A.
• Initial current is four times the steady-state current due to lower cold filament resistance.
• Thus, initial current is 4 × 2A = 8A.

Why D is correct:

• Ohm's law shows current I = P/V for steady state (2A), and the problem states initial current is four times this, yielding 8A.

Why the others are wrong:

• A: 0.25A ignores total power and surge factor, underestimating by factor of 32.
• B: 1.0A matches one lamp's steady current (60W/240V=0.25A ×4=1A) but forgets eight lamps.
• C: 2A is steady-state total current, not the initial surge.

Final answer: D