Voltage in a Parallel Circuit Electricity: voltage, parallel circuit Qty 1 1 1 2
Equipment and Materials PASPORT Xplorer GLX Voltage Probe (included with GLX) CASTLE Kit ‘D’ Cell
Part Number PS-2002 EM-8624A PI-6602
Purpose The purpose of this activity is to determine the relationship between voltage and the number of light bulbs that are connected to a voltage source in a parallel circuit.
Background Light bulbs in a parallel circuit are connected like steps of a ladder. Each light bulb is connected directly to the voltage source. If light bulbs are connected in parallel to a voltage source, what happens to the brightness of the individual bulbs as more bulbs are added to the “ladder”? What will happen to the voltage across each individual bulb as more bulbs are added to the circuit?
Fig. 1 Fi 1: Parallel P ll l circuit i it
Preview Use a Voltage Probe to measure the voltage across a voltage source (‘D’ cells) and the voltage across each bulb in a parallel circuit. Use the Xplorer GLX to record and display the voltage. Compare the voltages.
Predict 1.
How would the voltages across each light bulb in a parallel circuit change as more bulbs are added to the circuit?
2.
How would the brightness of the light bulbs in a parallel circuit change as more bulbs are added to the circuit?
3.
If one bulb in a parallel circuit is removed, what happens to the rest of the bulbs?
Safety Precaution •
Follow all directions for using the equipment.
Procedure GLX Setup 1.
Plug a Voltage Probe into the voltage input port on the left side of the Xplorer GLX and then turn on the GLX ( ). A graph of Voltage (V) and Time (s) will open.
to go to the Home Screen. Select Digits ) and press
to open the Digits screen.
Equipment Setup 1.
Put two D cells into the battery holder (from the CASTLE Kit). Put a round light bulb in a lamp socket.
2.
Use a pair of alligator clip patch cords to set up a circuit with the light bulb and voltage source.
•
Be careful to connect an alligator clip to the spring as shown.
3.
Leave one clip disconnected until you are ready to collect data.
Fig. 2: Digits display
Record Data: One Light Bulb 1.
Connect the ends of the Voltage Probe to the lamp socket in order to measure the voltage across the light bulb.
2.
Connect the clip to the voltage source to complete the circuit. Observe the brightness of the bulb.
3.
Press Start ( ) on the GLX to measure the signal from the Voltage Probe.
•
The voltage appears in the digits display.
4.
Record the voltage across the light bulb in the Data Table in the Lab Report section.
5.
Move the ends of the Voltage Probe to the alligator clips that are connected to the voltage source in order to measure the voltage across the two D cells.
6.
Record the voltage across the two D cells in the Data Table in the Lab Report section.
7.
Press to stop data recording. Disconnect the clip to the voltage source to open the circuit.
Connect a second light bulb in parallel with the first light bulb in the circuit.
2.
Connect the clip to the voltage source to complete the circuit. Record the apparent brightness of the two bulbs.
3.
Connect the ends of the Voltage Probe to the second lamp socket in order to measure the voltage across the second light bulb.
4.
Press Start ( ) on the GLX to measure the signal from the Voltage Probe.
5.
Record the voltage across the seco:nd light bulb in the Data Table in the Lab Report section.
6.
Next, move the ends of the Voltage Probe back to the first lamp socket to measure the voltage across the first light bulb.
7.
Record the voltage across the first light bulb in the Data Table.
8.
Finally, move the Voltage Probe back to the source and measure the voltage across the batteries.
9.
Press circuit.
Fig. 6: Two bulb setup
Fig. 7 Record voltage
to stop data recording. Disconnect the clip to the voltage source to open the
Record Data: Three Light Bulbs 1.
Connect a third light bulb in parallel with the other two light bulbs in the circuit.
2.
Repeat the procedure to measure the voltage across the source and across each of the light bulbs and record the voltages in the Data Table in the Lab Report.
Three Light Bulbs in Parallel Voltage Across Light Bulb 1: Voltage Across Light Bulb 2: Voltage Across Light Bulb 3: Voltage Across Batteries:
Questions 1.
How did the voltage across the two D cells compare to the voltage across the first light bulb?
2.
How did the voltage across each of the two light bulbs in parallel compare to the voltage across the D cells?
3.
What did you notice about the voltage across each light bulb and the voltage across the D cells when three bulbs are in parallel?
4.
What can you say about the voltage in a parallel circuit?
5.
What happened to the light bulbs when you removed the middle bulb from the socket? Why?
6.
If all the lights in a house are connected together in parallel and they are all turned on, what would happen to the lights when you turn one of them off (or it burns out)?
