A servo voltage stabiliser restricts the voltage output to 220V ± 1%.

1.	A servo voltage stabiliser restricts the voltage output to 220V ± 1%. If an electric bulb rated at 220V, 100W is connected to it, what will be the minimum and maximum power consumed by it?
Answer» Output voltage = 220 ± 1% 1% of 220V = 2.2v The resistance of bulb R = V²/P = (220)²/100 = 484Ω (a) For minimum power consumed V₁ = 220 – 1% = 220 – 2.2 = 217.8 ∴ i = V₁/R = 217.8/484 = 0.45A Power consumed = i × V₁ = 0.45 × 217.8 = 98.01W (b) for maximum power consumed V₂ = 220 + 1% = 220 + 2.2 = 222.2 ∴ i = V₂/R = 222.2/484 = 0.459 Power consumed = i × V₂ = 0.459 × 222.2 = 102W

A servo voltage stabiliser restricts the voltage output to 220V ± 1%. If an electric bulb rated at 220V, 100W is connected to it, what will be the minimum and maximum power consumed by it?

Answer»

Output voltage = 220 ± 1%

1% of 220V = 2.2v

The resistance of bulb R = V²/P = (220)²/100 = 484Ω

(a) For minimum power consumed V₁ = 220 – 1% = 220 – 2.2 = 217.8

∴ i = V₁/R = 217.8/484 = 0.45A

Power consumed = i × V₁ = 0.45 × 217.8 = 98.01W

(b) for maximum power consumed V₂ = 220 + 1% = 220 + 2.2 = 222.2

∴ i = V₂/R = 222.2/484 = 0.459

Power consumed = i × V₂ = 0.459 × 222.2 = 102W