Energy in Thermal Processes

Question: Three liquids are at temperatures of 10 degrees C, 20 degrees C and 30 degrees C, respectively. Equal masses of the first two liquids are mixed, and the equilibrium temperature is 17 degrees C. Equal masses of the second and third are then mixed, and the equilibrium temperature is 28 degrees C. Find the equilibrium temperature when equal masses of the first and third are mixed. I am not sure how to approach this problem. All my other problems in this chapter included much more specific information. The following equations are used in this chapter of Energy in Thermal Processes. Q = m c deltaT where m = mass, c = specific heat, and delta T = change in temperature. ... click for more

Laws of Thermodynamics

An ideal gas initially at pressure Po, volume Vo, and temerature To is taken through the cycle described in attached file. A) Find the net work done BY the gas per cycle in terms of Po and Vo. I believe that my answer of 2Po2Vo is correct. B)What is the net energy Q added to the system per cycle? I know that I have to find the change of internal energy for the system to find out Q based on the equation: delta U = Q + W. But where I am getting stuck is how to solve for U. U = 3/2nRT or U = 3/2 PV Can we assume that R = 1.00 mol? If so, I carry out solving for U and finally solving for Q to get RTo. I'm not sure this is right. This where I am unsure. C) Obtain a num... click for more

Currents

1. When electrons move through a metal conductor, a. they move in a straight line through the conductor. b. they move in zigzag patterns because of repeated collisions with the vibrating metal atoms. c. the temperature of the conductor decreases. d. they move at the speed of light in a vacuum. 2. A wire carries a steady current of 0.1 A over a period of 20 s. What total charge moves through the wire in this time interval? A. 200 C b. 20 C c. 2 C d. 0.005 C 3. If a 5.00 x 10^2 W heater has a current of 4.00 A, what is the potential difference across the ends of the heating element. a. 2.00 x 10^3 V b. 125 V ... click for more

Currents

1. In alternating current, the motion of the charges a. continuously changes in the forward and reverse directions. b. is equal to the speed of light. c. is greater than the speed of light. d. in the direction of the electric field. 2. A flashlight bulb with a potential difference of 4.5 V across it has a resistance of 8.0 ohm. How much current is in the bulb filament? a. 3.7 A b. 1.8 A c. 9.4 A d. 0.56 A 3. Which of the following wires would have the LEAST resistance? (Assume that the wires have the same cross-sectional area.) a. an aluminum wire 10 cm in length b. an aluminum wire 5 cm in length c. ... click for more

Currents 3

1. If a lamp is measured to have a resistance of 45 ohm when it operates at a power of 80 W, what is the current in the lamp? A. 2.10 A B. 1.3 A C. 0.91 A D. 0.83 A 2. If a lamp has a resistance of 120 ohm when it operates at a power of 1.00 x 10^2 W, what is the potential difference across the lamp? a. 110 V b. 120 V c. 130 V d. 220 V 3. An electric toaster requires 1100 W at 110 V. What is the resistance of the heating coil? a. 7.5 ohm b. 9.0 ohm c. 1.0 x 10^1 ohm d. 11 ohm Please show the work done, formulas used and the answer. Thank you!