Solution 1.20
p30 volt source = 30x(–6) = –180 W
p12 volt element = 12×6 = 72 W
Solution 1.21
60 0.5 A
120
p
p vi i v
= → = = =
Solution 1.22
Solution 1.23
Solution 1.24
Solution 1.25
A 1.2–kW toaster takes roughly 4 minutes to heat four slices of bread. Find the cost of
Solution 1.26
Solution 1.27
×==
3600 4 4h TLet (a)
.
)((
+===
∫ ∫∫
dt
t50
103vidtpdtW b)
0
T
0
T
Solution 1.28
A 150-W incandescent outdoor lamp is connected to a 120-V source and is left burning
continuously for an average of 12 hours per day. Determine:
(a) the current through the lamp when it is lit,
(b) the cost of operating the light for one non-leap year if electricity costs 9.5
cents per kWh.
Solution 1.29
Solution 1.30
Monthly charge = $6
Solution 1.31
In a household, a business is run for an average of 6 hours per day. The total power
consumed by the computer and its printer is 230 watts. In addition, a 75-W light runs
Solution 1.32
Solution 1.33
Solution 1.34
Solution 1.35
Solution 1.36
A battery can be rated in ampere-hours or watt hours. The ampere hours can be obtained
from the watt hours by dividing watt hours be a nominal voltage of 12 volts. If an
automobile battery is rated at 20 ampere-hours,
(a) what is the maximum current that can be supplied for 15 minutes?
(b) how many days will it last if it is discharged at a rate of 2 mA?
Solution 1.37
A total of 2 MJ are delivered to an automobile battery (assume 12 volts) giving it an
additional charge. How much is that additional charge? Express your answer in ampere-
hours.
Solution
Solution 1.38
Solution 1.39