Advertisements
Advertisements
प्रश्न
An immersion rod having resistance of 50 Ω is connected to 220V main supply. Assuming that all the energy generated goes to heat the water, calculate the time taken to heat 5 kg water from 30°C to 100°C.
Advertisements
उत्तर
We know that P = VI
∴ I = `"P"/"V" = 220/50 = 4.4`
Heat produced in an immersion heater
H = I2Rt
H = (4.4)2 × 50 × t
H = 968 t Joules
and Heat needed = mcθ
where C is the sp. heat capacity of water
= 4.2 × 103 J/kgC = 5 × 4.2 × 103 × (100 - 30)
= 5 × 4.2 × 103 × 70 = 1470000 J.
But Heat lost = Heat gained
968 t = 1470000
t = `1470000/968`
t = 1518.59 secs
t = 1518.6 secs
t = 25.326 min.
t = 25.33 mins.
APPEARS IN
संबंधित प्रश्न
State two factors on which the electrical energy consumed by an electrical appliance depends.
An electric lamp is labelled 12 V, 36 W. This indicates that it should be used with a 1 V supply. What other information does the label provide?
At a given time, a house is supplied with 100 A at 220 V. How many 75 W, 220 V light bulb could be switched on in the house at the same time (if they are all connected in parallel)?
Two resistors A and B of resistance 4 Ω and 6 Ω respectively are connected in parallel. The combination is connected across a 6 volt battery of negligible resistance. Calculate: (i) the power supplied by the battery, (ii) the power dissipated in each resistor.
Water in an electric kettle connected to a 220 V supply took 5 minutes to reach its boiling point. How long will it take if the supply voltage falls to 200 V?
What do you understand by ‘earthing’? What are the advantages of earthing in a household electric circuit? Explain, how it is done?
Two bulbs are rated: bulb A 100W, 120 V bulb B 10W, 120 V. If both are connected across a 120V supply, which bulb will consume more energy, When in series? Also calculate the current through each bulb in above cases.
