Solutions to Period 11 Exercises
E.1
On a cold morning your car starter motor
cranks for 10 seconds, drawing 60 amps
(= 60 coul/sec) of current from your 12
volt battery.
How much charge (in coul)
flowed through the starter motor?
a)
6 coul
b)
10 coul
c)
120 coul
d)
600 coul
Solve
I
=
Q/t
for
Q:
Q
=
I t
=
60 amps x 10 sec = 60 coul x 10 sec = 600 coul
sec
E.1
=
d
E.2
How much electric power (in watts) was
drawn by the starter motor in the previous
question?
a)
1.2 watts
b)
6 watts
c)
120 watts
d)
720 watts
P
=
I V
=
60 amps x 12 volts = 720 watts
E.2
=
d
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*Sign up*E.3
How much energy (in joules) did the
battery in Exercise E.1 supply ?
a)
1,200 joules
b)
6,000 joules
c)
7,200 joules
d)
144,000 joules
e)
198,000 joules
solve
P
=
E/t
for
E:
E
=
P t
=
720 watts x 10 sec = 720 joules x 10 sec = 7,200 J
sec
OR use
E
pot
=
Q V
= 600 coul x 12 V = 7,200 J
E.3
=
c
E.4
A rechargeable 1.25 volt
AA
battery for a
CD player is rated at 0.6 amp-hours.
How
much charge (in coul) is 0.6 amp-hours?
(Hint:

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