Physics 1402
Exam No. 2
Physic 1402 Test 2
Name___________________
Instructions: Show ALL work for partial credit.
Multiple Choice:
1.) Calculate the diameter of a 2cm length of tungsten filament ( = 5.6 x 10-8.m) in a
small lightbulb if its resistance is 0.050.
a.) 0.085mm
b.) 22mm
c.) 0.85mm
d.) 0.17mm
2.) Birds on a copper wire ( = 1.7 x 10-8 .m) rest with their feet 4cm apart. If the wire
has a diameter of 22cm and caries a current of 50A, what is the voltage difference across
the bird’s body?
a.) V
b.) x V
c.) x V
d.) V
3.) The following set of resistors is held at 12V. Find the current through each of the 2
resistors.
a.) 6 Amps
b.) 2 Amps
c.) 2.666 Amps
d.) 5.3 Amps
4.) Parallel plates are made by holding two 2m x 2m metal plates 0.5m apart. What
amount of charge is needed to bring the voltage between the plates to 200V?
a.) 8000 C
b.) 16000 C
c.) 2000 C
d.) 4000 C
5.) Reduce the following set of resistors to an equivalent resistance.
a.) 0.1333 
b.) 2.75 
c.) 4.8 
d.) 3.5 
6.) Two equal but opposite point charges (q = 2 x 10-9C) are located on the y axis 2m
apart as shown. The point P is on the x axis 5m from the origin. Find the Potential at
point P.
a.) 4 x 10-9V
b.) 18 x 10-9V
c.) 36 x 10-9V
d.) 0V
7.) If 4A of current goes into a branch point of 3 resistors and 1A comes out of the point
through a second resistor what current will come out of the point through the 3rd resistor?
a.) 1 Amp
b.) 2 Amps
c.) 3 Amps
d.) 4 Amps
8.) Why does the magnetic force never do work?
a.) Because the Magnetic Field is always perpendicular to the Magnetic Force.
b.) Because the Motion of the particle is always perpendicular to the Magnetic
Force.
c.) Because the acceleration is always perpendicular to the Magnetic Force.
d.) Because the Magnetic Field is always parallel to the Magnetic Force.
9.) Two conductors carry currents of 5 Amps in opposite directions and are separated by
0.1m. Find the magnitude and direction of the magnetic force per unit length between
the two currents.
a.) 2.75 x 10-5 N/m
b.) 1.57 x 10-5 N/m
c.) 5 x 10-5 N/m
d.) 5 N/m
10) The two currents shown below carry currents of 5 Amps in opposite directions and
are separated by 0.1m. Find the magnitude and direction of the magnetic field 0.2m
from the left current (P)
a.) 1.85 x 10-5 T
b.) 1.666T
c.) 8.57 T
d.) 5.666T
Short Answer:
11.) Explain how the Resistance: R = l/A and Capacitance: C = L/A equations are
“manufacturing” equations.
12.) Explain what is meant by the term “Drunkard’s Walk” and an example of how it
applies to Physics.
Show All Work:
13.) In the circuit below, find all the labeled currents:
14.) For the 4 charges shown below let q = 2.5C and x = 5m:
a.) Find the Potential at P.
b.) Find the amount of energy required to assemble these 4 charges.
15.) Find the charge on each Capacitor: