Measuring Temperature Using a Carbon Resistor

[vachan]

A carbon resistor is to be used as a thermometer. On a winter day when the temperature is 4.00(Degree C.), the resistance of the carbon resistor is 218.0(Greek "w') . What is the temperature on a spring day when the resistance is 215.8(Greek "W")?
Take the temperature coefficient of resistivity for carbon to be (alpha) = −5.00×10−4C^-1

I am not so sure how should i start... what equation should i apply in here? .

 

[f95toli]

What does the temperature coefficient of resistivity tell you?
(i.e. what does the number mean?)
Hint: Look at the unit

 

[vachan]

Thanks!

 

[vachan]

Electricity and Water Analogy

Consider the following water circuit: water is continually pumped to high pressure by a pump, and then funnelled into a pipe that has lower pressure at its far end (else the water would not flow through the pipe) and back to the pump. Two such circuits are identical, except for one difference: the pipes in one circuit have a larger diameter than the pipes in the other circuit. Through which circuit is the flow of water greater?

Small pipe
Large pipe

I am not so sure, if there have not tell me the velocity, how am i going to know?