An electric heater consumes 1.8 MJ when connected to a 250 V supply for 30 minutes. Find the current taken from the supply. Assuming the power rating of the heater is 1 kW.
Answers
Answer:
Explanation:
The heat added to tank ΔQ = Power x Time
ΔQ = 1.8 x 103 ×t(J)
The heat absorbed in water
ΔQ= mcΔQ =mcΔT =200×103×1×60=12×106cal
=12×1066×4.2J
Hence t= 12×106×4.21.8×103=2.78×104s=7.75h
Given info : An electric heater consumes 1.8 MJ when connected to a 250 V supply for 30 minutes.
To find : The current taken from the supply
solution : Energy consumed by electric heater, E = 1.8 MJ = 1.8 × 10⁶ J
voltage supply to heater, V = 250 volts.
time taken to supply, t = 30 minutes = 1800sec
using formula, P = Vit
here P = 1.8 × 10⁶ J, V = 250 volts , t = 1800 s
now, 1.8 × 10⁶ = 250 × i × 1800 sec
⇒i = (1.8 × 10³)/(25 × 18)
= (18 × 100)/(25 × 18)
= 4
Therefore the current taken from the supply is 4A.
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