Name: Dr. Julie J. Nazareth

Lab Partner(s): Physics 133L

Date lab performed: Section:

Basic Circuits

Follow the procedure as outlined in your lab manual.

Part A: Series Circuit

A-1: Connect the series circuit shown in figure 3 of your lab manual. Note what symbols are used to represent the light bulbs and the power supply in the figure, as well as the arrow showing the direction of conventional current flow.

Question A-1a) What happens when you unscrew one of the light bulbs from its socket? Be specific and explain why it happened. (Replace the bulb when done.)

Question A-1b) What happens if you increase the power supply voltage slightly?

Question A-1c) What would happen if you were to unscrew the other light bulb?

Connecting an ammeter:

Make sure that you DO NOT change the voltage setting on the power supply. Simply unplug the banana plug from the positive terminal of the power supply to connect or reconnect the ammeter in the circuit.

A-2: Connect the ammeter as shown in the left hand circuit drawing of figure 5. (Connect the ammeter in series BEFORE the first bulb to measure the current going into the first bulb, I1.)

Draw both a schematic diagram and a sketch of the real circuit for the left hand series circuit. The schematic diagram must include all of the elements in your real circuit , + and – signs at the power supply symbol indicating the positive and negative sides of the circuit, an arrow indicating the direction of the conventional current, and the resistors (light bulbs) labeled as bulb 1 (or R1) and bulb 2 (or R2). Use resistor symbols to represent the light bulbs since we are only concerned with the bulb’s electrical resistance. Please keep bulb 1 and 2 consistent throughout the lab.

Schematic diagram Real circuit

Connect the ammeter as shown in the right hand circuit drawing of figure 5. (Connect the ammeter BETWEEN the two bulbs to measure the current going into the second bulb, I2.)

Schematic diagram Real circuit

Table 1: Current measurements for series circuit

Current (bulb 1), I1 ( ) / Current (bulb 2), I2 ( ) / Relationship between I1 and I2

Connecting a voltmeter:

Make sure that you DO NOT change the voltage setting on the power supply. Simply unplug the banana plug from the positive terminal of the power supply to connect or reconnect the voltmeter in the circuit.

A-3: Connect the voltmeter as shown in the center circuit drawing of figure 7. Connect the voltmeter in parallel with the first bulb to measure the voltage across (from one side of the bulb to the other) the first light bulb, V1. Without changing the voltage on the power supply, connect the voltmeter in parallel with the second bulb only (left hand circuit drawing of figure 7) to measure the voltage, V2. Then, without changing the voltage on the power supply, connect the voltmeter across both bulbs (right hand circuit drawing of figure 7) to measure the voltage across the combination of light bulbs, V3.

Table 2: Voltage measurements for series circuit

Voltage (bulb 1), V1 ( ) / Voltage (bulb 2), V2 ( ) / Voltage (combination), V3 ( ) / Relationship between
V1 V2, and V3

Part B: Parallel Circuit

B-1: Connect the parallel circuit shown in figure 8 of your lab manual.

Question B-1a) What happens when you unscrew one of the light bulbs from its socket? Be specific and explain why it happened. (Replace the bulb when done.)

Question B-1b) What happens if you increase the power supply voltage slightly?

Question B-1c) What would happen if you were to unscrew the other light bulb?

For B-2 and B-3, DO NOT change the voltage setting on the power supply between the various circuit configurations. Simply unplug the banana plug from the positive terminal of the power supply to change your circuit.

B-2: Connect the ammeter in your circuit as shown in figure 10. (Connect the ammeter in series between power supply and only one of the bulbs, the top bulb.) Measure the current through the top bulb, I1, and record the value in table 3. Draw both a schematic diagram and a sketch of the real circuit that you made.

Ammeter reading of current through top bulb only

Schematic diagram Real circuit

Without changing the voltage on the power supply, reconnect the ammeter so it reads current through the bottom bulb only, I2. Draw both a schematic diagram and a sketch of the real circuit that you made.

Ammeter reading of current through bottom bulb only

Schematic diagram Real circuit

Without changing the voltage on the power supply, reconnect the ammeter so it reads current through the combination of both bulbs, I3. Draw both a schematic diagram and a sketch of the real circuit that you made.

Ammeter reading of current through combination of both bulbs

Schematic diagram Real circuit

Table 3: Current measurements for a parallel circuit

Current (top),
I1 ( ) / Current (bottom),
I2 ( ) / Current (combination), I3 ( ) / Relationship between
I1, I2, and I3

B-3: Connect the voltmeter in your circuit as shown in figure 11. (Connect the voltmeter across just one of the bulbs (the top one) and measure the voltage, V1. Record the value in table 4. Draw both a schematic diagram and a sketch of the real circuit that you made.

Voltmeter reading across top bulb only

Schematic diagram Real circuit

Without changing the voltage on the power supply, reconnect the voltmeter so it reads the voltage across the bottom bulb only, V2. Draw both a schematic diagram and a sketch of the real circuit that you made.

Voltmeter reading across bottom bulb only

Schematic diagram Real circuit

Without changing the voltage on the power supply, reconnect the voltmeter so it reads the voltage across the power supply output, V3. This is equivalent to the voltage across the combination of both bulbs in the parallel circuit. Make sure the rest of the circuit is still attached and the light bulbs are lit when you take your reading. Draw both a schematic diagram and a sketch of the real circuit that you made.

Voltmeter reading across power supply

Schematic diagram Real circuit

Table 4: Voltage measurements for parallel circuit

Voltage (top),
V1 ( ) / Voltage (bottom),
V2 ( ) / Voltage (across PS),
V3 ( ) / Relationship between
V1, V2, and V3

Turn the voltage on the power supply to zero. Turn off power supply. Dismantle your circuit.

Question 1 (Instead of summary/conclusion paragraph): What was the goal of, reason for, or purpose of the Basic Circuits lab? (Write your answer as if you were writing the introductory sentence to your summary/conclusion paragraph)

Question 2: What do your observations of current in this lab experiment you about the relationship of current from the power supply and through the resistors in (a) series circuits and (b) parallel circuits?

Question 3: What do your observations of voltage in this experiment tell you about the relationship of voltage provided by the power supply and across the resistors in (a) series circuits and (b) parallel circuits?

There is no conclusion/summaryparagraph for this lab experiment.

Lab: Basic Circuits Updated 09/13/12