Physics 108
Quiz #2
Experiment: DC Circuit
Spring 2015
Name:
TA:
Day/Time:
Section:
1. Three identical lightbulbs with resistance R are connected as shown in the circuit below. The
circuit also contains an open switch. If the switch is closed what will happen to the intensity of
bulb 1 and 2. (3pts)
i) bulb 1 gets brighter and bulb 2 gets dimmer
ii) bulb 1 gets dimmer and bulb 2 gets brighter
iii) no change
iv) both become brighter
1
v) both become dimmer
Ans:( i )(total resistance will decrease
hence total current will increase)
2
V
2. Each of the resistors in the diagram below has a resistance of 12 . The resistance of the entire
circuit is: (5pts) (please show your work clearly to get partial credit)
i) 1.4 
ii) 10 
iii) 60 
iv) 12 
v) None of these
Ans: (ii)
(12/3+12/2= 10 )
3
3. Consider the circuit shown below.
A. What is the equivalent resistance of this circuit? (5 pts)
B. Solve for the total current ( I ) in the circuit (3 pts)
(show your work clearly)
Ans:
A. Equivalent resistance= 9.5 
B. Total current =12/9.5= 1.26 A
I
2