**USEFUL CONSTANTS: q (electron) =
-1.6 x 10 ^{-19} C
**

5] A small night light operates with a
current
of 50 milliamps. If the light is turned on for 8.0

hours, how much charge moved
through the filament?

Answer: 1.4 x 10^{3}
C

6] The filament of an automobile parking
light
bulb develops 25 watts of power when connected

to the car’s 12 V battery.
What is the resistance of the filament when operated under these

conditions? Would
the resistance of the filament be the same when the bulb is
disconnected

(no current flowing
through it)?

Answer: 5.7 W
, NO

1] Find the currents I_{1} , I_{2} , and I_{3}
for the circuit shown below

ANSWER: I1 = +1.0 A , I2 = -1.0 A , I3 = 0.0 A

2] Find the equivalent resistance between points **a** and **b**
for the resistor combination shown below.

All resistors have a value of 1.0 Ohm.

ANSWER: R equivalent = 1.6 Ohm or
8/5 Ohm

8] The filament of an automobile parking
light
bulb develops 25 watts of power when

connected
to the car’s 12 V battery. If the filament is made of tungsten wire

(r = 5.6 x 10^{-8} W
m) with a cross sectional area of 3.2 x 10^{-7} m^{2} ,
how long is the wire?

(remember, there are lots of little coils in filaments)

Answer: 33 meters

Multiple Choice
Examples

a)
conservation of electricity

b) conservation of mass

c) conservation of charge

d) conservation of energy

e) conservation of momentum

a. 4 times as large

b. twice as large

c. unchanged

d. half as large

e. one quarter as large

Answers:

1. c

2. d