(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Air passes over an electrical heater at a steady rate of 2500cm^3 per second. The inlet temperature of the air is 20^oC ( 20 degrees celcius ) and the steady outlet temperature is 40^0C ( 40 degrees celcius)

a) What heat is absorbed by air passing over the heater in 2 hours

b) Obtain an estimate for the power rating of the heater

Density of air ( 1.2 kgcm-3)

Specific heat capacity of air : 1000 J-1Kg-1K-1

2. Relevant equations

So I think that I should use the equation Q=mcΔθ

3. The attempt at a solution

Here's what I did :

2500cm^3=2500g=2.5kg

Since 2.5kg is heated every second then 2hrs of heating would heat 2.5x7200 = 18,000kg of air.

ΔθOutlet-Inlet temperature = 40-20 = 20 degree celcius change in temperature,

Specific Heat capacity of air : 1000 Jkg-1K-1

Q=mxcxΔθ

= 18000x1000x20

=3.6x10^8

Which is wrong because the answer at the back of the book had 4.32x10^5. I've tried, but I really need some help :) Thanks

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Air passes over an electrical heater at a steady rate of 2500cm^3 per second.

**Physics Forums | Science Articles, Homework Help, Discussion**