Midterm—Physics II Lab, Spring 2012
50 pts
Name___________________________
Equations:
V  IR
R
L
A
Req , parallel 
1
R1

1
R2
1
 R13  ...
Rx  R
Rb
Ra
Req ,series  R1  R2  R3  ...
Multiple Choice (1 pt each)
____
1.
If the resistance in a circuit is constant and the current is increased, how will the voltage be
affected?
a.
Decreases
c.
Increases
b.
Does not change
____
2.
If 3 resistors are connected in parallel, what is equal across each resistor?
a.
Current
c.
Resistance
b.
Potential (Voltage)
d.
None of the Above
____
3.
If you increase the diameter of a wire, what happens to the resistance?
a.
Increases
c.
Remains the same
b.
Decreases
d.
Depends on the resistivity
____
4.
Equipotential lines are always ___________ to electric field lines.
a.
Parallel
c.
at 45 degree angles
b.
Perpendicular
d.
Tangent
____
5.
What is the purpose of a wheatstone bridge?
a.
to measure an unknown resistance
b.
to measure an unknown voltage
c.
d.
to measure an unknown current
to confound its user
Short Answer
1. (4 pts) Draw 6 electric field and 6 equipotential lines for this configuration of charges. Let the lines
span across the entire page.
2. (9 pts) Given this data for a particular circuit consisting of a resistor in series with a power supply,
determine (graphically) the voltage provided by the power supply. Use the attached graph paper.
R ( ohms)
1
2.4
3.2
5.4
8
11
I (amps)
3.3
1.6
1.2
0.5
0.4
0.2
V=______________
3. (3 pts) Consider this circuit. What is the potential of the battery?
V=__________________
4. (5 pts) Three resistors of 2, 10, and 8 Ω are in series with a power supply providing 40 V. What is
the current and potential in each of the resistors?
5. (7 pts) Consider the following circuit. What is the equivalent resistance? What is the potential
across each resistor? What is the current through each resistor?
Req=_____________
V1= _____________
V2= _____________
V3= _____________
I1= _____________
I2= _____________
I3= _____________
6. (4 pts) What components or parts make up an ammeter?
7. (3 pts) How do you hook up an ammeter in a circuit?
8. (3 pts) How can you increase the range of a voltmeter?
9. (7 pts) This figure shows a Wheatstone Bridge. Derive the equation for the unknown resistance R x.
Show all steps.