Download Phet Parallel Circui..

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Light Bulbs in Parallel
Circuit 1
1. Drag and drop one light bulb and one battery in the work area. Drag and drop wires to connect the
battery to the light bulb. Once the circuit is completed, the bulb should light
and you should see the flow of charge from positive to negative end of the
battery through the circuit. This is circuit 1.
2. Use a voltmeter (check the box next to voltmeter on the right side of the
display) to measure the voltage across the bulb. Use the non-contact
ammeter to measure the current in the wires. Use Ohm’s Law (V=IR) to
Calculate the resistance of the bulb. Right click on the light bulb and check
“show value” box. Does this agree with your calculations? Record results
below.
Voltage across light bulb=
Bulb 1
Battery
Voltage across
Current in the wires=
V
Is the current the same in all wires?
Current
through - I
Calculate R:
No
Resistance
Answer here
Ohms ( V/I)
Circuit 2. Two bulbs in parallel
1.Set up a second circuit with one battery and two bulbs in parallel as shown below. This is
circuit 2. Use the voltmeter and the non-contact ammeter to measure the values listed below.
Bulb 1
Voltage across
V
Current
through - I
Resistance
Ohms ( V/I)
Bulb 2
Battery
Sum
Inverse Sum!
Not V/I
No
Answer here
Notice that the current coming from the battery splits. Some of it goes to bulb 1 and the rest goes to bulb 2.
The total current should be I1 + I2 = Ibattery Put the values in the table.
Calculating the total ( equivalent) resistance in a parallel circuit is a bit trickier. It is based on the fact that the
voltage is the same for all resistive devices and the current is
additive is a pure parallel circuit .
Your circuit has two 10 Ohm light bulbs (symbol Ω). Calculate
the total or equivalent ( what one resistor is equivalent)
resistance for your circuit. I like to call this “Inverse Sum”.
Really it’s more like Inverse of the inverse sum.
Show your work below and place your answer on the table above
Circuit 3. Three bulbs in parallel
1. Set up another circuit with three bulbs in parallel as shown below. This is circuit 3. Use the voltmeter and
the non-contact ammeter to measure the values listed below.
A
B
C
D
Bulb 1
Bulb 2
Bulb 3
Battery
Voltage across
V
Current
through - I
No
Answer here
SUM
Resistance
Ohms ( V/I)
Inverse SUM!
Not V/I
No
Answer here
Once again current splits at each junction point. The total current at A should equal to the sum of the currents
going to each light bulb ( B+C+D). The Battery voltage should be the same as the voltage across each light
bulb.
Your circuit has Three 10 Ohm light bulbs (symbol Ω). Calculate
the total or equivalent ( what one resistor is equivalent)
resistance for your circuit. I like to call this “Inverse Sum”.
Really it’s more like Inverse of the inverse sum.
Show your work below and place your answer on the table above
1. Does the brightness of the bulbs change as you add more bulbs in parallel?
2. What happens to the overall resistance connected to the battery as you add more bulbs in parallel?
3. What happens to the current through the battery as you add more bulbs in Parallel?