Working with heat and matter.

1. How much heat is required to raise the temperature by 10 degrees Celsius of one kg of water and iron? 2. Two identical objects (the same mass, material) at temperatures T1 = 20 degrees and T2 = 30 degrees are in contact. What is the final temperature of these objects after they reach thermal equilibrium?

First year physics

Qn 3. The transfer of heat from the body's interior to the surface is achieved primarily through the flow of blood. In cold surroundings blood flow near the skin is reduced by constriction of capillaries. This allows the skin to provide the insulation. Skin temperature can drop to as low as 15 degrees reducing the heat loss from the skin to the environemnt while the body maintains its normal temperature of about 37 degrees. When your skin temperature is 29 degrees what is the effective average thickness of the insulating layer of tissue separating the skin at 29 degrees from the body interior at 37 degrees. (assume the average surface area of a typical person is 1.5m squared and the a... click for more

Direct Currents

1. What happens when you turn the key in the ignition of your automobile? Should you start your car on a cold rainy night with the wipers, lights, heater and defroster all on? Explain. 2.Take an ordinary metal-body flashlight. Explain how it works and discuss the significance of the arrangement of the dry cells. 3.High voltage cables are generally uninsulated, and a bird standing on one of them may have its feathers puffed up. Why? Why aren't our little feathered friends electrocuted on their perches? Could a chicken walk safely on the third rail of an electrified railroad? Multiple Choice: 1. The difference in potential between the electrodes of a voltaic cell when there is no c... click for more

Direct Currents

Multiple Choice 1. The resistance of a superconducting material drops, essentially to zero, rather suddenly when: (a) the sample is heated above Tc (b) the sample is exposed to a magnetic field (c) the sample is cooled below Tc (d) the sample experiences a current Ic (e) none of these. Explain your choice. 2. Imagine a length of ordinary insulated hookup wire. The wire's resistance is not dependent on: (a) the conductor's length (b) the conductors radius (c) the material making up the insulator (d) the material making up the conductor (e) none of these. Explain your choice. Problem 1. A particle accelerator contains two beams flowing side-by-side in opposite directions; the beams... click for more

Circuits

Multiple choice: 1. An ideal source of emf is connected in seriew with a resistor in closed loop, and a current or 0.e50 A circulates. An additional 6.0-Ohm resistor is added in series, and the current drops to 0.30 A. The original resistance was: (a) 9.0 Ohm (b) 6.0 Ohm (c) 15 Ohm (d) 3.0 Ohm (e) none of these. Explain your choice. 2. A 24-W, 12-V ohmic lamp is placed in a circuit with 6 V across it, at which tiem it draws a current of: (a) 2 A (b)1 A (c) 0 (d) 1/2 A (e) none of these. Explain your choice. 3. A battery of emf 12 V and internal resistance of 0.2 Ohm is placed across a variable resistor. The resistor is adjusted until it dissipates a maximum amount of power, at which p... click for more