34.An electric heater operating at 220volts boils 5litre of water in 5minutes.If it is used on 110volts, it will boil the same amount of water in
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P = V² / R Heat H = P * t => t = H/P = R H / V²
If V is halved, then Power is 1/4 th. So the time duration is 4 times ie., 20 minutes.
If V is halved, then Power is 1/4 th. So the time duration is 4 times ie., 20 minutes.
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We know , H=V²t/R
Given , V₁ = 220 v.
V₂ = 110 v .
t₁ = 5 m.
t₂ = 10 n.
H₁ = H₂.
The amount of heat required to heat the same amount of water will be same.
The resistance will also be same.
V₁² × t₁ / R₁ = V₂² t₂ / R²
= > R₁ = R₂.
= > V₁² × t₁ = V₂² t₂
So,
220² × 5 = 110² × 10
= > 4840 × 5 = 1210 × 10
= > n = 4840/1210 × 5
= > 4 × 5
= > 20 minutes.
The time will be 20 minutes .
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