Download Ohms Law and Circuits KEY

IPC
HS/Science
Unit: 11 Lesson: 01
Ohm’s Law and Circuits KEY
Note: Student answers may vary, depending on the battery used and the actual resistance in
the bulbs.
Materials (per group):
•
•
•
•
•
voltmeter (1)
flashlight bulbs (3)
6 volt battery (1) (or 4 D batteries in series)
ammeter (1)
wires (10)
Directions:
Label your bulbs (1–3), and then build the following circuits.
Create a series circuit with the three bulbs and battery.
2. Use the ammeter to measure the current passing through each resistor. (Connect the ammeter
in series right after each bulb. You will need to repeat this for each bulb.) Fill in the data chart with
the appropriate data.
3. Use the voltmeter to measure the voltage drop across each bulb. (Place the posts on either
side of the bulb.) Fill in the data chart with the appropriate data.
4. Remove one bulb, leaving a series circuit with two bulbs and a battery. Repeat steps 2 and 3.
Fill in the data chart with the appropriate data.
5. Create a parallel circuit with the three bulbs and battery.
6. Use the ammeter to measure the current passing through each resistor. (Connect the ammeter
in series right after each bulb. You will need to repeat this for each bulb.) Fill in the data chart with
the appropriate data.
7. Use the voltmeter to measure the voltage drop across each bulb. (Place the posts on either
side of the bulb.) Fill in the data chart with the appropriate data.
8. Remove one bulb, leaving a parallel circuit with two bulbs and a battery. Repeat steps 6 and 7.
Fill in the data chart with the appropriate data.
1.
Data table:
Relative
Brightnes
s
(low or
high)
Current
through
Bulb 1
amps
Current
through
Bulb 2
amps
Current
through
Bulb 3
amps
Total
Current
amps
Potential
across
Bulb 1
volts
Potential
across
Bulb 2
volts
Potential
across
Bulb 3
volts
Total
Potential
volts
Circuit #1
(3 Bulbs)
Low
.1A
.1A
.1A
.1A
.5V
.5V
.5V
1.5V
Circuit #2
(2 Bulbs)
High
.15A
.15A
XXXX
.15A
.75V
.75V
XXXX
1.5V
SERIES
©2012, TESCCC
01/16/13
page 1 of 2
Relative
Brightness
(low or
high)
Current
through
Bulb 1
amps
Current
through
Bulb 2
amps
Current
through
Bulb 3
amps
Total
Current
amps
Potential
across
Bulb 1
volts
Potential
across
Bulb 2
volts
Potential
across
Bulb 3
volts
Total
Potential
volts
Circuit #3
(3 Bulbs)
High
.30A
.30A
.30A
.90A
1.5V
1.5V
1.5V
4.5V
Circuit #4
(2 Bulbs)
High
.30A
.30A
XXXX
.60A
1.5V
1.5V
XXXX
3.0V
PARALLEL
1. Diagram series Circuit #1 using the corresponding symbols for the resistors and battery.
(The diagram should be in a series circuit with three resistors with the appropriate symbol
and one battery with the appropriate symbol.)
2. Diagram parallel Circuit #3 using the corresponding symbols for the resistors and battery.
(The diagram should be in a parallel circuit with three resistors on parallel branches with
the appropriate symbol and one battery with the appropriate symbol.)
In the series circuit, how does the total current change from using all three bulbs to only using
two? How does it change in the parallel circuit?
3.
The current increases in a series circuit, and it decreases in a parallel circuit.
In the series circuit, how does the total potential change from using all three bulbs to only using
two? How does it change in the parallel circuit?
4.
In the series, the total voltage stays the same while in the parallel circuit the total voltage
decreases.
In the series circuit, how are the individual currents through the bulbs related to the total
current? Repeat for voltage across the bulbs.
5.
The current in the series is the same across each bulb, and it is the same as the total
current in the circuit. The voltage is the same across each bulb and adds up to the total
voltage provided by the battery.
In the parallel circuit, how are the individual currents through the bulbs related to the total
current? Repeat for voltage across the bulbs.
6.
In the parallel circuit, the current was the same across each branch but was a portion of
the total current coming from the battery. The voltage across each branch was the same as
the battery but was a portion of the total voltage of the whole circuit.
7.
How is the brightness of the light bulbs related to the structure of your circuit?
The bulbs in the parallel circuit stayed the same high brightness, regardless of the number
of bulbs. The bulbs in the series circuit became dimmer as more were added.