# Thermal equilibrium

1. Dec 12, 2005

### JJMezzapesa

I have been trying to figure this problem out for a while now and get stuck everytime. I do not understand how to go about it. Any help would be greatly appriciated.

An aluminum rod and an iron rod are joined end to end in good thermal contact. The two rods have equal lengths and radii. The free end of the aluminum rod is maintained at a temperature of 100 degrees celcius, and the free end of the iron rod is maintained at 0 degrees celcius. (a) Determine the temperature of the interface between the two rods. (b) If each rod is 15 cm long and each has a cross-sectional area of 5.0 cm2(squared), what quantity of energy is conducted across the combination in 30 minutes?

2. Dec 12, 2005

### mezarashi

Thermal equilibrium means the heat transfer dQ/dt is constant at all cross-sections. Apply the conduction equation at the interface for aluminum and iron.

3. Dec 12, 2005

### JJMezzapesa

how do you determine the temperature using the conduction equation when there are two different materials, thus two different thermal conductivity constants?

4. Dec 12, 2005

### JJMezzapesa

I do not understand this problem either.

A U-TUBE AT BOTH ENDS IS PARTIALLY FILLED WITH WATER. OIL (DENSITY = 750KG/M2) IS THEN POURED INTO THE RIGHT ARM AND FORMS A COLUMN L=5.00 CM HIGH. DETERMINE THE DIFFERENCE h IN THE HEIGHTS OF THE TWO LIQIUD SURFACES. THE RIGHT ARM IS THEN SHIELDED FROM ANY AIR MOTION WHILE AIR IS BLOWN ACROSS THE TOP OF THE LEFT ARM UNTIL THE SURFACES OF THE TWO LIQUIDS ARE AT THE SAME HEIGHT. DETERMINE THE SPEED OF OF THE AIR BEING BLOWN ACROSS THE LEFT ARM. ASSUME THE DENSITY OF AIR IS 1.29 KG/M2