Name:_____________
Physics 10
Benjamin
Homework
Current in a Circuit: Batteries & Bulbs 2
Problem C
First, answer all of the questions with your predictions of what will happen. Then try it out in class (or
on the simulation online), and explain what you see, comparing it you what you expected.
Bulb A
Bulb B
Bulb C
Imagine that you build circuit 7. You notice that all the bulbs
are the same brightness. Since there is only one path, each
bulb has the same amount of current running through it.
Then, imagine that you connect another bulb across Bulb B
(call it Bulb X). You notice that the brightnesses of the other
bulbs change. Justify each of your answers (you may need
additional paper).
Circuit 1
1. What did adding Bulb X do to the resistance between
Bulb A and Bulb C?
[increase]
[decrease]
[stay the same]
Bulb X
2. What did adding Bulb X do to the total resistance of the
circuit?
Bulb A
Bulb B
Bulb C
[increase]
[decrease]
[stay the same]
3. What did adding Bulb X do to the total current through
the battery?
[increase]
[decrease]
[stay the same]
Circuit 2
4. What did adding Bulb X do to the current through Bulb
B?
[increase]
[decrease]
5. Which of the bulbs got brighter when you added Bulb X?
6. Which of the bulbs got less bright when you added Bulb X?
[stay the same]
Problem D
When current is offered a path of effectively no resistance, effectively all the current will be in that
path. In the illustration of circuit 9, the current does not travel through bulb B, but through the wire
shown instead. We call this a short circuit, and say that Bulb B has been shorted out.
1. When the wire
is added to
circuit 9, does
the brightness of
either Bulb A or
Bulb C change?
Bulb A
Bulb B
Circuit 1
2. Redraw circuit 9, and move the wire so that Bulb A is
shorted out instead of B.
A
3. In circuit 10, draw a wire connecting two points so that
Bulb C is shorted out.
What happens to Bulbs A and B? Try it out in class or on
the simulation.
B
C
4. Redraw circuit 10 with a single wire attached that will
short out bulbs A and B.
Circuit 2
Bulb C
Problem E
B
A
C
Circuit 1
D
Circuit 2
1. Rank the four bulbs in the circuits shown above from brightest to least bright. All batteries are
identical (same voltage), and all bulbs are identical (same resistance).
Ranking:
Justify your answer:
2. Answer the questions about circuit 1 above (don’t worry about bulb D). Explain each answer.
a. What will to happen to the other bulbs if you were to unscrew bulb A?
b. Replace A with a wire?
c. Unscrew bulb B?
d. Replace C with a wire?
Problem F
D
C
E
1. Rank the bulbs in circuit 3 from brightest
to dimmest.
Ranking:
A
B
Justify your answer:
Circuit 1
2. Answer the questions about the circuit above. Explain each answer.
a. What will to happen to the other bulbs if you were to unscrew bulb A?
b. Replace C with a wire?
c. Unscrew D?
d. Replace E with a wire?