A 60 W bulb operates at 120 V. Its resistance is MCQ with Answer and Explanation

Explanation:
M = 1 + D/f when image at near point (D = 25 cm). For infinity, M = D/f. So max at near point.

Explanation:
Power factor = cosφ, where φ is phase angle between voltage and current. Also, power factor = R/Z (resistance/impedance) for series circuits, and = true power (W) / apparent power (VA). Thus both (a) and (c) are correct definitions. Memory tip: 'Power factor = cosφ = R/Z = P/S; ideal = 1 (purely resistive)'. This definition question tests AC circuit knowledge, crucial for competitive exams. Always link power factor to energy efficiency: low power factor means more current for same power, increasing losses.

Explanation:
Significant figures rules: leading zeros are not significant; trailing zeros after decimal are significant. Thus 0.00250: leading zeros (before 2) not significant; digits 2,5,0 are significant (trailing zero after decimal counts). So three significant figures. Memory tip: 'Start counting at first non-zero digit; include trailing zeros after decimal'. This measurement precision concept is frequently tested in competitive exams. Always apply rules consistently: 0.0025 has two sig figs; 0.00250 has three, indicating higher precision.