LIGHT BULB CIRCUITS - I
COMMON MISCONCEPTIONS OF ELECTRICAL CIRCUITS
A. When a circuit is closed, charge begins flowing from one end of the battery (which one?) through
the circuit until it gets to the other end of the battery. This belief will result in a prediction that bulbs
will light up in some progressive order when the switch is closed.
B. Charge gets “used up” as it flows through the circuit. This belief will result in a prediction that bulbs
will get progressively dimmer as they make their way back to the battery.
C. The battery is a constant source of energy or current. This belief will result in a prediction that
adding or removing circuit elements will not change the total current or energy delivered by the battery,
which implies that single bulbs near the battery will not change their brightness.
D. The battery produces a fixed amount of brightness that is shared or divided among bulbs,
regardless of their number or arrangement. This belief may result in incorrect predictions regarding
the order of bulb brightness in combination light bulb circuits, and how the brightness of bulbs change
when one bulb goes out.
ACTIVITY:
Use the circuit materials (cells, cell holders, wire, Christmas tree lights,
switch, etc…) and the DC Circuit Construction Kit computer simulation
found at http://phet.colorado.edu/web-pages/simulations-base.html to
construct and investigate the following circuits.
EFFECTS OF ADDITIONAL CELLS IN SERIES ON BULB BRIGHTNESS
1. Connect a single bulb in series with one dry cell
and a switch. Notice the brightness of the bulb.
2. Add another dry cell in series with the first. Describe
any changes in the brightness of the bulb.
3. Add one more dry cell in series with the first two.
Describe any changes in the brightness of the bulb.
4. Based on what you discovered in previous
investigations with dry cells, what change(s) occur
when additional cells are added in series?
5. Why does the change(s) described in the preceding question affect the bulb brightness?
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EFFECTS OF ADDITIONAL CELLS IN PARALLEL ON BULB BRIGHTNESS
1. Connect a single bulb in series with one dry cell
and a switch. Notice the brightness of the bulb.
2. Add another dry cell in parallel with the first.
Describe any changes in the brightness of the bulb.
3. Add one more dry cell in parallel with the other two.
Describe any changes in the brightness of the bulb.
4. Based on what you discovered in previous
investigations with dry cells, what change(s) occur
when additional cells are added in parallel?
6. Why doesn’t the change(s) described in the preceding question affect the bulb brightness?
MULTIPLE BULBS IN SERIES
1. Connect a single bulb in series with three dry
cells and a switch. Notice the brightness of the bulb.
2. Connect another bulb in series with the first.
Compare the brightness of the two bulbs to each
other, and to the brightness of the single bulb.
3. Connect a third bulb in series with the other two.
Again compare the brightness of the three bulbs
in series to each other, and to the brightness of
the bulbs in the previous two circuits.
4. Connect a fourth bulb in series with the other three. Again compare the brightness of the four
bulbs in series to each other, and to the brightness of the bulbs in the previous three circuits.
5. Describe what happens to the brightness of individual bulbs as more and more are connected in
series.
6. Does the order of bulb placement affect their brightness? ______ What would you have
students do to find out the answer to this question?
7. When the switch is first closed, do all bulbs in series light at the same time, or one after the
other?
8. What happens to the brightness of the other bulbs when one bulb goes out?
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MULTIPLE BULBS IN PARALLEL
1. Connect a single bulb in series with three dry cells
and a switch. Notice the brightness of the bulb.
2. Connect another bulb in parallel with the first.
Compare the brightness of the two bulbs to each
other, and to the brightness of the single bulb.
3. Connect a third bulb in parallel with the other two.
Again compare the brightness of the three bulbs in
series to each other, and to the brightness of the
bulbs in the previous two circuits.
4. Connect a fourth bulb in parallel with the other three. Again compare the brightness of the four
bulbs in series to each other, and to the brightness of the bulbs in the previous three circuits.
5. Describe what happens to the brightness of individual bulbs as more and more are connected in
parallel.
6. Does the order of bulb placement affect their brightness? ______ What would you have
students do to find out the answer to this question?
7. When the switch is first closed, do all bulbs in parallel light at the same time, or one after the
other?
8. What happens to the brightness of the other bulbs when one bulb goes out?
3 BULBS IN COMBINATION (i.e., not all series or parallel)
1. Construct a combination circuit containing
a switch, three bulbs, and three D-cells.
Draw a schematic diagram of this circuit.
Label these bulbs A, B, and C. Below the
circuit, rank the bulbs from brightest to
dimmest. (Example: X > Y = Z)
2. Construct another combination circuit
containing a switch, three bulbs, and three D-cells.
Draw a schematic diagram of this circuit.
Label these bulbs A, B, and C. Below the
circuit, rank the bulbs from brightest to
dimmest. (Example: X > Y = Z)
3
4 BULBS IN COMBINATION (i.e., not all series or parallel)
1. Construct a combination circuit containing
a switch, four bulbs, and three D-cells.
Draw a schematic diagram of this circuit.
Label these bulbs A, B, C, and D. Below
the circuit, rank the bulbs from brightest to
dimmest. (Example: X > Y = Z > W)
2. Construct another combination circuit
containing a switch, four bulbs, and three
D-cells. Draw a schematic diagram of this
circuit. Label these bulbs A, B, C, and D.
Rank the bulbs from brightest to dimmest.
(Example: X > Y = Z > W)
3. Construct another combination circuit
containing a switch, four bulbs, and three
D-cells. Draw a schematic diagram of this
circuit. Label these bulbs A, B, C, and D.
Rank the bulbs from brightest to dimmest.
(Example: X > Y = Z > W)
4. Construct another combination circuit
containing a switch, four bulbs, and three
D-cells. Draw a schematic diagram of this
circuit. Label these bulbs A, B, C, and D.
Rank the bulbs from brightest to dimmest.
(Example: X > Y = Z > W)
5. Construct another combination circuit
containing a switch, four bulbs, and three
D-cells. Draw a schematic diagram of this
circuit. Label these bulbs A, B, C, and D.
Rank the bulbs from brightest to dimmest.
(Example: X > Y = Z > W)
4
Draw schematic diagrams to the right of each of these circuits. Without actually constructing
them, label the bulbs (A, B, C, etc….) and state the order of bulb brightness.
A.
B.
C.
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