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.
संबंधित प्रश्न
When an electric lamp is connected to 12 V battery, it draws a current of 0.5 A. The power of the lamp is:
(a) 0.5 W
(b) 6 W
(c) 12 W
(d) 24 W
In a filament type light bulb, most of the electric power consumed appears as:
(a) visible light
(b) infra-red-rays
(c) ultraviolet rays
(d) fluorescent light
An electric bulb is rated at 220 V, 100 W. (a) what is its resistance? (b) what safe current can be passed through it?
Two bulbs are rated 60 W, 220 V and 60 W, 110 V respectively. Calculate the ratio of their
resistances
Why is the heating element of an electric oven wound on a helix? State the reason.
How does earthing prevent electrical shock?
Find the energy released by a current of 0.25 amperes flowing through a heater for 5 minutes. The p.d. is 230 V.
1 kWh is equal to:
A fuse is rated 5 A. Can it be used with a geyser rated 1540 W, 220 V Write Yes or No. Give supporting calculations to justify your answer.
