Question 1 (a) In Fig. 25-19a, are capacitors 1 and 3 in series? yes no (b) In Fig. 25-19a, are capacitors 1 and 2 in parallel? yes no (c) Rank the equivalent capacitances of the four circuits shown in Fig. 25-19, greatest first.
b > c > d > a a > b = c > d b = c > a = d a = b = c = d Question 2 In the figure find the equivalent capacitance of the combination. Assume that C 1 = 12.9 µf, C 2 = 6.46 µf, and C 3 = 3.25 µf. Question 3 In the figure find the equivalent capacitance of the combination. Assume that C 1 = 12.7 µf, C 2 = 7.44 µf, and C 3 = 4.09 µf.
Question 4 In the figure a 15 V battery is connected across capacitors of capacitances C 1 = C 6 = 5.0 μf and C 3 = C 5 = 2.5C 2 = 2.5C 4 = 5.5 μf. What are the (a) potential V 3 across and (b) charge q 3 (in C) on capacitor 3? (a) (b) *2 - significant digits are disabled; the tolerance is +/-2% *2 - significant digits are disabled; the tolerance is +/-2% *3 - significant digits are disabled; the tolerance is +/-2% *4 - significant digits are disabled; the tolerance is +/-2% *5 - significant digits are disabled; the tolerance is +/-2% *6 - significant digits are disabled; the tolerance is +/-2% *7 - significant digits are disabled; the tolerance is +/-2% *8 - significant digits are disabled; the tolerance is +/-2% *9 - significant digits are disabled; the tolerance is +/-2% 0 - significant digits are disabled; the tolerance is +/-2% 1 - significant digits are disabled; the tolerance is +/-2%
Question 5 Figure 26-19 shows four situations in which positive and negative charges move horizontally and gives the rate at which each charge moves. Rank the situations according to the effective current through the regions, greatest first. If multiple situations rank equally, use the same rank for each, then exclude the intermediate ranking (i.e. if objects A, B, and C must be ranked, and A and B must both be ranked first, the ranking would be A:1, B:1, C:3). If all siuations rank equally, rank each as '1'. (a) (b) (c) (d) 1. Greatest 2. Second greatest 3. Third greatest 4. Fourth greatest Question 6 The (United States) National Electric Code, which sets maximum safe currents for insulated copper wires of various diameters, is given (in part) in the table below. Which wire gauge has the maximum safe current density? ( Gauge is a way of identifying wire diameters, and 1 mil = 10-3 in.) Significant digits not applicable; exact number, no tolerance Question 7
A small but measurable current of 3.4 x 10-10 A exists in a copper wire whose diameter is 3.7 mm. The number of charge carriers per unit volume is 8.49 x 10 28 m -3. Assuming the current is uniform, calculate the (a) current density and (b) electron drift speed. (a) (b) *2 - significant digits are disabled; the tolerance is +/-2% *2 - significant digits are disabled; the tolerance is +/-2% Question 8 A conducting wire has a 1.1 mm diameter, a 2.7 m length, and a 70 mω resistance. What is the resistivity of the material? Question 9 Flying Circus of Physics Kiting during a storm. The legend that Benjamin Franklin flew a kite as a storm approached is only a legend he was neither stupid nor suicidal. Suppose a kite string of radius 2.21 mm extends directly upward by 0.827 km and is coated with a 0.505 mm layer of water having resistivity 179 Ω m. If the potential difference between the two ends of the string is 169 MV, what is the current through the water layer? The danger is not this current but the chance that the string draws a lightning strike, which can have a current as large as 500 000 A (way beyond just being lethal). Question 10 A 100 W lightbulb is plugged into a standard 120 V outlet. (a) How much does it cost in dollars per 31-day month to leave the light turned on continuously? Assume electrical energy costs US$ 0.07/kW h. (b) What is the resistance of the bulb? (c) What is the current (in A) in the bulb? (a) (b) *2
(c) *3 - significant digits are disabled; the tolerance is +/-2% *2 - significant digits are disabled; the tolerance is +/-2% *3 - significant digits are disabled; the tolerance is +/-2% Question 11 How much energy (in kj) is consumed in 2.29 h by an electrical resistance of 407 Ω when the potential applied across it is 90.7 V?