 Dynamics Track
Inclined Plane
Momentum

Capacitor
Plate Sep
Plate Sep/Volt
Dielectrics

Circuits
Ohms Law
Series/Parallel

Wave Tank
Freq/Wavelength
Two Pt Interf.

Optical Bench
Refraction
Focal Length

Circuit Experiment Board

Series and Parallel Circuits

In this lab you will work with two circuits, one series and one in parallel.   Each of these circuits will use the same three resistors.   You will apply a DC voltage to the circuit and measure the current through and voltage across each resistor.   First you will do some calculations with circuits similar to those you will model in the lab.

Refer to the following schematic: 1. What kind of circuit is this?
2. What is the net resistance of this circuit?
3. What is the current drawn from the battery?
4. What is the power consumed by this circuit?

Complete the following table:

 Resistance 330Ω 560Ω 1000Ω Current Voltage Power

Refer to the following schematic: 1. What kind of circuit is this?
2. What is the net resistance of this circuit?
3. What is the current drawn from the battery?
4. What is the power consumed by the circuit?

Complete the following table:

 Resistance 330Ω 560Ω 1000Ω Current Voltage Power

Purpose:

The purpose of this lab is to investigate the relationship between current and voltage in a series and parallel circuits.

Equipment:

• Digital multimeter
• Circuit Experiment Board
• Jumpers
• Resistors

Cautions:

This equipment is delicate.   Everything should go together with the lightest of touches.   Do not force anything!

Familiarization with the Circuit Experiment Board and initial circuit setup:

Position the Circuit experiment board with the clear tube at the top and the resistor connections at the bottom.   There should be four resistors already installed in the resistor connection area.   You will not use the leftmost resistor.   There should be one battery installed in the battery holder.   Refer to the diagram below when setting up the circuits. Creating and measuring a Series Circuit

### Measuring the actual resistances of the three resistors:

1. Turn the meter on.
2. Turn the meter knob to “2k” in the “Ω” range
3. Make sure that the black meter lead is in the black terminal of the meter.
4. Make sure that the red meter lead is in the red terminal of the meter
5. Touch the red meter lead to one side of the 330Ω resistor.
6. Touch the black meter lead to other side of the resistor.
7. Read the meter reading.   Since it is in kiloohms, multiply the number by 1000 and record it next to “Actual Resistance” in the table below:
8. Repeat the same procedure for the 560Ω and 1000Ω    resistors, entering their values into the table.

Series Circuit Table:

 Nominal Resistance 330Ω 560Ω 1000Ω Actual Resistance Voltage Current Power

Creating a Series Circuit:

1. Use a short jumper to connect pad F with pad G.
2. Use a short jumper to connect pad C with pad D.
3. Use a long jumper to connect pad H with the “─” terminal of the battery.   The circuit is now complete except for one connection.   You will make this connection with the meter to measure current.

### Measuring current drawn from the battery

1. Turn the meter knob to “2m” in the “A” range
2. Make sure that the black meter lead is in the “COM” terminal of the meter.
3. Move the red meter lead to the “A” terminal of the meter
5. Touch the black meter lead to the “+” terminal of the battery.
6. Read the meter.   It is in milliamps, so divide the number by 1000 and record the value here:

Series Battery Current

Completing the circuit:

1. Use a long jumper to connect pad B with the “+” terminal of the battery.   The circuit is now complete and drawing current.   Do not leave it connected for too long, as it will drain the battery.   If you are delayed, open the circuit by removing the wire from the”+” terminal.

Measuring Voltages across the resistors:

1. Move the red meter lead to the red terminal of the meter
2. Turn the meter knob to “2” in the “V” range
3. Make sure that the black meter lead is in the “COM” terminal of the meter.
4. Touch the red meter lead to the end of the 330Ω resistor connected to the B pad.
5. Touch the black meter lead to the end of the 330Ω resistor connected to the F pad.
6. Read the meter reading.   Record it next to “Voltage” in the 330Ω column.
7. In the same manner, measure the voltage across the 560Ω resistor and the 1000Ω resistor and record them in the table.

Measuring the battery voltage:

1. Touch the red meter lead to the “+” terminal of the battery.
2. Touch the black meter lead to the “─” terminal of the battery.
3. Record the meter reading here:

Series Battery Voltage

Measuring Currents through the resistors:

In order to measure currents through a resistor, you have to temporarily disconnect one end of the resistor and put the meter in series with it.

1. Turn the meter knob to “2m” in the “A” range
2. Make sure that the black meter lead is in the “COM” terminal of the meter.
3. Move the red meter lead to the “A” terminal of the meter
4. Disconnect the end of the 330 Ω resistor from pad F by gently lifting it straight up until it is free of the spring.
5. Touch the red meter lead to one of the springs on the F pad.
6. Touch the black meter lead to the free end of the 330 Ω resistor.   You may hold it in place with your finger.   The voltage is low.
7. Read the meter reading.   Since it is in milliamps, divide the number by 1000 and record it in the table next to “Current” in the “330 Ω” column.
8. Reconnect the 330 Ω resistor to its spring on pad F.
9. In the same manner, measure the currents through the 560 Ω resistor and the 1000Ω resistor, putting the meter in series with each resistor in turn to get a reading.   Record the currents in the appropriate spaces in the table.

Creating and measuring a Parallel Circuit

Converting the circuit from a series to a parallel circuit:

1. Remove the long jumper from the “+” terminal of the battery and from the B pad.   This stops the circuit from draining the battery while you add jumpers.
4. Check to be sure that pads B, C, and D are connected by jumpers.
5. Check to be sure that pads F, G, and H are connected by jumpers.
Measuring the actual resistances of the three resistors:

Actually, you’ve already done this.   Simply copy the resistance values from the Series Circuit Table into the Parallel Circuit Table!

Parallel Circuit Table:

 Nominal Resistance 330Ω 560Ω 1000Ω Actual Resistance Voltage Current Power

### Measuring current drawn from the battery

1. Turn the meter knob to “20m” in the “A” range
2. Make sure that the black meter lead is in the “COM” terminal of the meter.
3. Make sure that the red meter lead is in the “A” terminal of the meter
5. Touch the black meter lead to the “+” terminal of the battery.
6. Read the meter reading.   Since it is in milliamps, divide the number by 1000 and record it here:

Parallel Battery Current

Completing the circuit:

1. Use a long jumper to connect pad B with the “+” terminal of the battery.   The circuit is now complete and drawing current.   Do not leave it connected for too long, as it will drain the battery.   If you are delayed, open the circuit by removing the wire from the”+” terminal.

Measuring Voltages across the resistors:

1. Move the red meter lead to the red terminal of the meter
2. Turn the meter knob to “2” in the “V” range
3. Make sure that the black meter lead is in the “COM” terminal of the meter.
4. Touch the red meter lead to the end of the 330Ω resistor connected to the B pad.
5. Touch the black meter lead to the end of the 330Ω resistor connected to the F pad.
6. Read the meter reading.   Record it next to “Voltage” in the 330Ω column.
7. In the same manner, measure the voltage across the 560Ω resistor and the 1000Ω resistor and record them in the table.

Measuring the battery voltage:

1. Touch the red meter lead to the “+” terminal of the battery.
2. Touch the black meter lead to the “─” terminal of the battery.
3. Record the meter reading here:

Parallel Battery Voltage

Measuring Currents through the resistors:

In order to measure currents through a resistor, you have to temporarily disconnect one end of the resistor and put the meter in series with it.

1. Turn the meter knob to “20m” in the “A” range
2. Make sure that the black meter lead is in the “COM” terminal of the meter.
3. Move the red meter lead to the “A” terminal of the meter
4. Disconnect the end of the 330 Ω resistor from pad F by gently lifting it straight up until it is free of the spring.
5. Touch the red meter lead to one of the springs on the F pad.
6. Touch the black meter lead to the free end of the 330 Ω resistor.   You may hold it in place with your finger.   The voltage is low.
7. Read the meter reading.   Since it is in milliamps, divide the number by 1000 and record it in the table next to “Current” in the “330 Ω” column.
8. Reconnect the 330 Ω resistor to its spring on pad F.
9. In the same manner, measure the currents through the 560 Ω resistor and the 1000Ω resistor, putting the meter in series with each resistor in turn to get a reading.   Record the currents in the appropriate spaces in the table.

### Cleaning up

1. Remove all jumpers from the circuit board and set them aside.
2. Turn the meter off.
3. Turn the meter knob to “2k” in the “Ω” range
4. Make sure that the black meter lead is in the black terminal of the meter.
5. Move the red meter lead is in the red terminal of the meter.
6. Make sure that everything is as you found it.

Now the equipment is set up for the next lab group.   You may now return to the classroom to complete the lab activity.

Completing the tables:

1. For each resistor in each table, multiply the voltage and current figures and record the result in the power row.

Series Circuit Questions:

Refer to the Series Circuit Table to answer the following:

1. How did the currents compare between the three resistors of the series circuit?   Was there much difference?   If so, which resistor had the most current and which had the least?

2. How did the voltages compare between the three resistors of the series circuit?   Was there much difference?   If so, which resistor had the most voltage and which had the least?

3. How did the powers compare between the three resistors of the series circuit?   Was there much difference?   If so, which resistor had the most power and which had the least?

4. Multiply the Series battery voltage that you measured and recorded by the Series battery current and record your answer here:

6. Compare the answers to the previous two questions.   Are they identical, close, or far apart?   Which major conservation law does this illustrate?

8. Compare your answer to the Series Battery Voltage figure you measured.   Are they identical, close, or far apart?   Which of Kirchoff’s rules does this illustrate?

Parallel Circuit Questions:

Refer to the Parallel Circuit Table to answer the following:

1. How did the currents compare between the three resistors of the parallel circuit?   Was there much difference?   If so, which resistor had the most current and which had the least?

2. How did the voltages compare between the three resistors of the parallel circuit?   Was there much difference?   If so, which resistor had the most voltage and which had the least?

3. How did the powers compare between the three resistors of the parallel circuit?   Was there much difference?   If so, which resistor had the most power and which had the least?

4. Multiply the Parallel Battery Voltage that you measured and recorded by the Parallel Battery Current and record your answer here:

6. Compare the answers to the previous two questions.   Are they identical, close, or far apart?   Which major conservation law does this illustrate? 