First law of thermodynamics: fridge, meteorite, and fan

[Jason_Hyde]

Hi,
I was woundering if somebody could explain to me using the equation
ΔU = Q + W (The first law of thermodynamics)

• how a fridge works?
• what happens with a meteorite?
• what happens with a standard fan?

Much appreciated
--
Regards
Jason_Hyde

 

[Andrew Mason]

Hi,
I was woundering if somebody could explain to me using the equation
ΔU = Q + W (The first law of thermodynamics)

To be clear: W here is the work done to the system. Q is the heat flow into the system minus the heat flow out of the system.

• how a fridge works?
• what happens with a meteorite?
• what happens with a standard fan?

We aren't going to give you the answer but we can help you find the answer.

The first question is a matter of applying the first law of thermodynamics to a reversed heat engine cycle (which extracts work from heat flowing from a hot to a cold reservoir) to cause heat to flow from a cold to a hot reservoir by adding work to the system.

For the second, think of the kinetic energy of the meteorite doing work on the Earth's atmosphere.

For the third example, think of the fan as doing work on air (a gas) by creating a low pressure on one side and a high pressure on the other.

AM