Ionization of donor impurities in semiconductors. A pentavalent impurity (called a donor) introduced in place of a tetravalent silicon atom in crystalline silicon acts like a hydrogen atom in free space, but with e2 /e playing the role of e2 and an effective mass m* playing the role of the electron mass m in the description of the ionization energy and radius of the ground state of the impurity atom, and also for the free electron. For silicon the dielectric constant € = 11.7 and, approximately, m* = 0.3 m. If there are 1017 donors per cm", estimate the concentration of conduction electrons at 100 K.

Which statement best describes resistance? resistance is a. how well a current will flow in a material and is measured in volts. b. how well a material conducts an electrical charge and is measured in ohms. c. the ability of a material to attract a positive charge to create a current. d. the ability of a material to repel neutral charges and is measured in ohms.

Use henry's law and the solubilities given below to calculate the total volume of nitrogen and oxygen gas that should bubble out of 1.7 l of water upon warming from 25 ˚c to 50 ˚c. assume that the water is initially saturated with nitrogen and oxygen gas at 25 ˚c and a total pressure of 1.0 atm. assume that the gas bubbles out at a temperature of 50 ˚c. the solubility of oxygen gas at 50 ˚c is 27.8 mg/l at an oxygen pressure of 1.00 atm. the solubility of nitrogen gas at 50 ˚c is 14.6 mg/l at a nitrogen pressure of 1.00 atm. assume that the air above the water contains an oxygen partial pressure of 0.21 atm and a nitrogen partial pressure of 0.78 atm.

James joule carefully measured the difference in temperature of the water at the top and bottom of a waterfall. why did he expect a difference