Problem 4.19 Suppose you have enough linear dielectric material, of dielectric constant er, to half-fill a parallel-plate capacitor (Fig. 4.25). By what fraction is the capacitance increased when you distribute the material as in Fig. 4.25(a)? How about Fig. 4.25(b)? For a given potential difference V between the plates, find E, D, and P, in each region, and the free and bound charge on all surfaces, for both cases.

A hot tub with a surface area of 28 ft2 is filled with water to a depth of 29 in . Hint: volume is calculated as area × height (A × h). A) What is the volume of water in the tub, in liters? Express your answer to two significant figures and include the appropriate units. B) How many kilojoules are needed to heat the water from 59∘F to 103 ∘F? Express your answer to two significant figures and include the appropriate units. C) If the hot-tub heater provides 5900 kJ/min, how long, in hours, will it take to heat the water in the hot tub from 59∘F to 103∘F? Express your answer to two significant figures and include the appropriate units.

A bacteria colony which is unrestricted in its growth will grow out in a circular manner. The population ?(?) of the colony at time t is directly proportional to the area of the circle. Suppose that a particular bacteria grows in such a way that the population is 1.3 times larger each day, and that initially (t=0) the colony has a diameter of 4 centimeter and a population of 7 million. a) Find the Population and Diameter of the colony on the fifth day. b) Find the Rate of Change of the Population and Diameter of the colony on the fifth day. c) Unrestricted growth models are often impractical as values will quickly become unreasonable. On what day does our model predict that the area of the bacteria colony will be 1 square mile?