Capter continued carges on te plates were reversed, te droplet would accelerate downward since all forces ten act in te same direction as gravity. 5. A 0.5-F capacitor is able to store 7.0 0 C of carge wit an electric field strengt of 0.33 N/C between its plates. How far apart are tese plates? C d 4.40 3 m 4.4 mm 6. Most capacitors are measured in terms of microfarads, F, or picofarads, pf, because te unit of capacitance, te farad, is a relatively large unit. Given a -F capacitor wit plates separated by.0 mm and an electric field strengt of N/C, calculate te number of electrons resting on te plates of tis capacitor. C EC CEd ( F)( N/C)(0.000 m) 0.000 C n e Ed 7.0 0 C (0.33 N/C)(0.50 6 F) Ed 0.000 C.0 9 C 6.0 5 electrons Capter. A 9.0- battery is connected to a ligtbulb, as sown below. 9.0- Battery a. How muc power is delivered to te ligtbulb? I (0.50 A)(9.0 ) 4.5 b. How muc energy will te bulb use in? E t I E It (0.50 A)(9.0 )() 6,000 c. How long would te bulb ave to stay on to use k of energy? E t t E I t I E 0.50 A E ( k) 0 00 k 36 00 s 3.60 6 3. 606 t (0. 50 A)( 9.0 ) 800,000 s Ligtbulb 74 Supplemental roblems ysics: rinciples and roblems
Capter continued. A - ligtbulb is connected to a 5- power source. a. at is te current troug te ligtbulb? I I 5 0.5 A b. at is te resistance of te ligtbulb? ( 5 ) 00 3. A circuit is set up as sown in te diagram at te top rigt. a. at sould te reading on te ammeter be? I I 36 4.5 A b. at sould te reading on te voltmeter be? I I (.5 A)(4 ) 36 c. How muc power is delivered to te resistor? I (.5 A)(36 ) 54 d. How muc energy is delivered to te resistor per our? E t (54 )(30 s).90 5 36 4. A microwave draws a 5.0-A current from a 0- power source. a. How muc power is delivered to te microwave? I (5.0 A)(0 ) 800 b. How muc energy does te microwave use to eat food for? E t (800 )( s) 00,000 5. A circuit is set up as sown in te diagram below. a. at is te resistance of te resistor in te circuit? I 5.7 A 43 b. at sould be te reading on te voltmeter? I I (.7 A)(43 ) 0 A I 4 ysics: rinciples and roblems Supplemental roblems 75
Capter continued c. How muc power is delivered to te resistor? I (.7 A)(5 ) 30 d. How muc energy is delivered to te resistor per our? E t (30 )(30 s).0 6 8. A - ligtbulb as a resistance of 40. at is te current in te ligtbulb? I I ( ) ( 40 ) 0.5 A 9. at is te current troug an 80.0- resistor if te voltage drop across te resistor is 0.0? I 5 6. A 00- ligtbulb is turned on for twofifts of te time for 30 s. At a price of $0.090 per k, ow muc does te ligtbulb cost to run during te 30 s? E t (30 s) 5 (4 /)(30 s/),036,800 s E (00 )(,036,800 s).03680 8 (.03680 8 ) k 3.6 0 6 8.8 k (8.8 k)($0.090/k) $.59 7. A current of 0.85 A is measured troug a 7- resistor for.00. How muc eat does te resistor generate? E t I E I t (0.85 A) (7 )(30 s) 7.00 4.7 A I 0. 0 8 0. 0 0.50 A 0. A - ligtbulb and a 00- ligtbulb bot are connected to a 0- power source. ic bulb as te greater resistance? ( 0 ) 00 00 ( 0 00 00 ) Te - ligtbulb as te greater resistance.. A - battery is used to power a 3.00 ma video camera. a. How muc power does te battery provide to te camera? 3.00 ma 0.30 A I (0.30 A)( ) 3.6 b. How muc energy does te camera use in.0 s? E t (3.6 )(.0 s) 3.6 76 Supplemental roblems ysics: rinciples and roblems
Capter continued c. How muc energy does te camera use in.0? E t (3.6 )(.0 ).30 4 d. How long would it take te video camera to use k of energy? E t t E I t I E k (000 /s)(30 s) t 3.60 6 (3.60 6 ) (0.30 A)( ).00 6 s or about 80. A - bulb powered by a 0.0- source as a resistance of 5.0 at room temperature and 00.0 at operating temperature. a. at is te current wen a - bulb is turned on at room temperature? 0.0 I 4 A 5. 0 b. at is te power of tis roomtemperature bulb? ( 0.0 ).9 k 5.0 c. at is te current wen te - bulb is at operating temperature? ( 0. 0 ) I (.00 A 00. 0 ) d. at is te power of te bulb at operating temperature? ( 0. 0 44.0 00. 0 3. A 40- water eater as a resistance of 5. a. at is te power of te eater? (4 0.0 ) 3.8 k 5 ) b. at termal energy is supplied by te eater in 5? E t (3.8 k)(5 ) 3.40 3 k c. Compare te power of te same 40- water eater to a 0- water eater, also wit a resistance of 5. ( 0 ) 9 0.96 k 5 3.8 k 4.0 0.96 k Te power of te 40- water eater is four times greater tan te power of te 0- eater. d. Compare te termal energy of te 40- water eater to a 0- eater in a 5- period. E t (0.96 k)(5 ) m in 8 k 3.4 03 k 4.0 8 k Te energy of te 40- water eater is four times greater tan tat of te 0- eater. 4. How muc power is dissipated in wires tat ave a current of 50.0 A and a resistance of 0.05? I (50.0 A) (0.05 ) 38 5. A long-distance ig-tension wire uses 500,000. a. at is te power output of tese wires in watts, kilowatts, and megawatts if te current is 0 A? I (0 A)(500,000 ) 0 7 0 4 k 0 M ysics: rinciples and roblems Supplemental roblems 77
Capter continued b. at is te power dissipated in te wires if te resistance is 0.05? I (0 A) (0.05 ) 6 6. otovoltaic panels provide power to a ome eac sunny. Te resistance of te wires in tis system is 0.5. If te power consumption of a computer in te ome is 00, wat current does te computer cause troug te wires? I I 00 0.5 0 A 7. Compare te energy a 0- bulb uses per our wit te energy use in.0 our of a - bulb. E 0 t (0 )(.0 ) m in 4.30 5 E t ( )(.0 ) 0 5 E 0 4.305 E6 0 05 Te 0- bulb uses twice te energy in an our. 8. How muc money would be saved by turning off one 00.0- ligtbulb 3.0 / for 365 s if te cost of electricity is $0. per k? E t (00.0 ) 3.0.0 6 /. 0 6 k 3.6 0 6 0.3 k/ 0.3 k da y $0. k $0.04/ $ 0.04 (365 s) $4. 9. How muc money can be saved by turning off a 500.0- television set for 3.0 / for 365 s at $0. per k? E t (500.0 ) 3.0 5.40 6 / (5.40 6 k ).5 k/ 3.60 6.5 k $ 0. k $0.8/ $ 0.8 (365 s) $65.70 0. How muc does it cost to operate a 000.0- blow dryer for 0.0 utes at $0. per k? E t (000.0 )(0.0 ) 6.000 5 (6.000 5 k ) 0.7 k 3.60 6 (0.7 k) $ 0. k $0.0 78 Supplemental roblems ysics: rinciples and roblems