A 100 W immersion heater is placed in a pot containing 1 litre of water at 20-C- How long will it take to heat water to boiling temperature- if 20 - of the available energy is lost to surroundings -

P = 100 W, Δθ = 100^∘ 20^∘ = 80^∘ m = Vρ = 1000 × 10^ 6× 1000 = 1 kg Used power= 80% 80% P = Et = ms Δθt 80100 P = ms Δθt 45× 100 = 1 × 4200 × 80t ⇒ t = ...

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Standard X

Physics

Effect of High Latent Heat of Fusion of Ice

A 100 W immer...

Question

A $100 W$ immersion heater is placed in a pot containing $1 litre$ of water at $20^{\circ} C$ . How long will it take to heat water to boiling temperature. if $20 %$ of the available energy is lost to surroundings ?

32 minutes

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44 minutes

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70 minutes

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60 minutes

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Solution

The correct option is C $70 minutes$
$P = 100 W, Δ θ = 100^{\circ} - 20^{\circ} = 80^{\circ}$

$m = V ρ = 1000 \times 10^{- 6} \times 1000 = 1 kg$

Used power $= 80 %$

$80 % P = \frac{E}{t} = \frac{m s Δ θ}{t}$

$\frac{80}{100} P = \frac{m s Δ θ}{t}$

$\frac{4}{5} \times 100 = \frac{1 \times 4200 \times 80}{t}$

$\Rightarrow t = 4200 s$

$t = \frac{4200}{60} min$

$= 70 min$

Hence, option (c) is the correct answer.

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A 100 W immersion heater is placed in a pot containing 1 litre of water at 20∘C. How long will it take to heat water to boiling temperature. if 20% of the available energy is lost to surroundings ?

The correct option is C 70 minutesP=100W, Δθ=100∘−20∘=80∘ m=Vρ=1000×10−6×1000=1kg Used power=80% 80%P=Et=msΔθt 80100P=msΔθt 45×100=1×4200×80t ⇒t=4200 s t=420060 min =70 min Hence, option (c) is the correct answer.

A $100 W$ immersion heater is placed in a pot containing $1 litre$ of water at $20^{\circ} C$ . How long will it take to heat water to boiling temperature. if $20 %$ of the available energy is lost to surroundings ?