Lab 02 - Resistors

Overview

In this Lab, we will be building basic resistor circuits and measuring the changes in voltage and current that occur when resistances change within a circuit.

Basic Circuits

1. Locate the resistors in the table and record the following values.

This is the resistor color code. It is used to identify the value of a given resistor, based on the colors in order. The resistors we will use in lab are all three band, to identify them, look for the gold tolerance band, then, starting from the oppopposite side, the bands will be, in order, the first digit, the second digit (as in 1 is the first digit and 0 is the second, making 10) then the third will be the number of zeros following. Thus, brown black brown would be 100 ohms.

Definitions

Open Circuit: There is no connection. The resistance is infinite.

Closed Circuit: There is a connection with no or negligible resistance. The value is approximately zero.

5.) Given the color codes in the table below determine the nominal resistance value of the resistor. The nominal value is the ideal value. You can ignore the tolerance.

Component	1st	2nd	3rd	Tolerance	Value
R1	Brown	Black	Brown	Gold
R2	Brown	Black	Red	Gold
R3	Brown	Black	Orange	Gold
R4	Orange	Orange	Brown	Gold
R5	Yellow	Violet	Brown	Gold
R6	Yellow	Violet	Red	Gold
R7	Brown	Black	Yellow	Gold
R8	Orange	Orange	Red	Gold

5.) We will be using an arduino's 5v rail as a power source and two resistors. The resistors are labeled R1 and R2.

Power Conventions

Use a red wire for the positive terminal of the power supply.

Use a black wire for the ground. Any ground will suffice. The blue line at the bottom is the ground rail. Any connection to this rail connects to the power supply ground.

Resistor Layout

The top resistor is R1. It connects from the 9V power supply to R2.

The bottom resistor is R2. It connects from the bottom of R1 to ground on the power source.

Classical Current Flow

Current leaves the battery or power supply from the positive terminal, passes through the circuit, and then returns to the battery or power supply to the negative terminal. A complete circuit is necessary for current to flow.

Schematic diagram for Test Circuit 1

Explanation

The 9V battery is connected to resistor R1 and then resistor R2 which is then connected back to the negative or ground terminal. Volt meter AM1 measures the voltage across R1. Volt meter AM2 measures the voltage across R2. Ammeter AM3 is connected in series between R2 and the ground terminal to measure the current in the circuit. The current leaving the battery, going through R1, then going through R2 returns to the battery through the negative terminal.

A Physical Diagram of the Test Circuit

R1 is in series with R2. There is only one path for the current to flow through the circuit. So, I_total = I_battery = I_R1 = I_R2.

A Simpler Schematic Diagram of the Circuit.

6.) Take all the measurements in Tinkercad and fill in the table. R1 remains the same in all cases. Change the value of R2 with each resistor from the table in turn. Record the measurements, and fill in the table.

If you have not already done so watch the video for the lab, create the circuit, and simulate the circuit for each of the R2 resistor values below.

R1	R2	Vin	VR1	VR2	VR1 + VR2	It
1000Ω	1000Ω	5v
1000Ω	100Ω	5v
1000Ω	470Ω	5v
1000Ω	3.3KΩ	5v
1000Ω	4.7KΩ	5v
1000Ω	10KΩ	5v
1000Ω	100KΩ	5v

Notes:

1000 Ω = 1K Ω

4700 Ω = 4.7K Ω

10000 Ω = 10K Ω

100000 Ω = 100K Ω

7.) Accuracy check of the measurements in your table. Add V_R1 to V_R2 and place the result in the last column. The sum of these voltages should equal the supply voltage.

8.) Save your Tinkercad circuit under the name “ELE111 Circuit Lab 1.