Lab 1-2 Basic Electrical Circuits

 

Requirement

Check

Created circuit

 

Added switch

 

Drawing of circuit

 

Measured voltage

 

Measured amps

 

Answered questions

 

Cleaned up station

 

 

 

Objective

The objective of this lab exercise is to demonstrate and define basic concepts and terminology related to the study and use of electricity. After completing this lab exercise, you will be able to:

7  _ Create a simple switched circuit.

7  _ Describe the relationship among voltage, amperage, ohms, and wattage.

7  _ Use a multimeter to measure voltage and amperage.

 

Materials Required

7  _ One 9-volt battery

7  _ Electronic Playground and Learning Center

7  _ Four pieces (two short, two long) of standard-grade electrical wire

 

 

ACTIVITY

Creating a circuit

  1. Connect your 9volt Battery to the board.
  2. Take your long wires.
  3. Attach one to LED2s first lead (3). To attach, bend the spring, slip the exposed end of the wire in between the springs.
  4. Take the end of that wire and attach it to the first spring on the battery (26)
  5. Now attach another wire between 4 and 27.
  6. What happens?

 

 

 

 

7.       Why?

 

Creating a Circuit with a Switch

1.       Disconnect your wires from the battery.

2.       Connect one long wire from 3 to the 10kΩ connector. Notice that you see a little resistor there. A resistor resists or slows the flow of energy. Remember that.

3.       Now connect one long wire from 4 to 26.

4.       Take your two small wires. Connect one from 27 to 56. Push the button. What happens?

 

5.       Why?

 

6.       Where do you need to connect the other small wire to create a circuit controlled by the switch?

 

7.       Not move your wires from the 10kΩ to the 1kΩ and push the switch.

 

8.       Turn on the light and what happens? Is the light brighter, or dimmer?

 

9.       Why?

 

10.   Which of those resistors slows the flow of energy down more?

 

11.   What do you think will happen if you attach the leads to the 100kΩ resistor?

 

12.   This is Ohms Law in action! Ohms law states that

 

Current= voltage divided by resistance…or the higher the resistance, the lower the current flows. If you have lower resistance, the faster the current can flow. Voltage is what makes the current flow. Lower resistance=brighter LED.

 

13.   Look at each of your resistors very closely. What do you notice about them?

 

 

 

 

14.   Draw the following resistors and label the colors of their bands

 

Resistor

Drawing

1kΩ

 

10kΩ

 

100kΩ

 

 

 

 

The color bands tell you what the resistor is.

·         The first ring is the first digit of the resistor’s value

·         Second ring is the second digit of the resistor’s value

·         Third ring tells you the power of ten to multiply by (or the number of zeroes to add)

·         Fourth ring tells you the construction tolerance. Most have a gold band for 5% tolerance, which means that it is guaranteed to offer resistance within 5% of the marked value. (So a 100kΩ transistor with a gold band would offer resistance from 95 to 105Ω).

 

Color table

Color

Value

Black

0

Brown

1

Red

2

Orange

3

Yellow

4

Green

5

Blue

6

Violet

7

Gray

8

White

9

 

So a resister that had a bands, in order: red, violet, orange, gold would be translated as

27X103=27000Ω with a 5% tolerance.

 

  1. In the space provided below, draw a diagram demonstrating the flow of electricity in the circuit you have created. Be sure to note the direction of the current’s flow.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Measuring voltage

1.       Configure your multimeter to measure the voltage of your circuit.

a.       Connect the red lead to the VΩmA jack

b.      Connect the black lead to the COM jack

2.       Attach the +/- leads from your multimeter to the respective +/- sides of the battery (26 and 27). You can just touch the wires connected to those positions.

3.       Turn the dial on your multimeter to the closest voltage measurement you expect to see (hint…this is a NINE volt battery).

4.       What voltage do you see on the window (it’ll change, but should settle within a few seconds)?

 

 

 

 

5.       Now with the help from a friend, take the leads and touch the wires leading out of 3 and 4 by the light. Have someone push the switch. What is the voltage?

6.       Why is it different from the answer you got above? What is between the battery and the LED?

7.       Change the resistance from 10kΩ to 1kΩ. Now what is the voltage with the switch on?

 

 

 

Measuring amps (current)

1.       Amps are measured with the current running, since it’s a measurement of current.

2.       Configure your multimeter to measure the amps of your circuit.

a.       Plug in the red wire to the VΩmA jack

b.      Plug in the black wire to the COM jack

c.       Turn the dial to the Amp area (see directions…hint, Amp starts with A) closest to the amperage you expect to find. If you don’t know, set it to the highest one and change until you get a reading that seems reasonable.

3.       Have a friend hold down the switch.

 

4.       Touch the leads to 3 and 4. Record the amperage.

5.       Now let go of the switch and what readings do you get? Why?

 

 

6.       Now take and touch the leads (without pressing the switch) to the wires at 55 and 56. What happens?

 

7.       Why?

 

 

Because of this you must be very careful when testing amperage in a live circuit because you CAN complete that circuit.  Your multimeter must have a high enough rating to handle the current.

 

Review Questions

 

Circle True or False.

1. Resistance is measured in ohms. True / False

2. A switch can act as a break in a circuit. True / False

3. AC is the acronym for ampere. True / False

4. A multimeter can measure only voltage. True / False

5. In a circuit, amps and volts are always the same amount when measured. True / False

6. Describe the difference in multimeter placement for measuring volts and amps.

 

Lab Notes

7  What does AC mean?—Alternating current (AC) is current that cycles back and forth rather than traveling in only one direction. Normally between 110 and 125 AC volts are supplied from a standard wall outlet.

7  What are amps?—Amps are units of measurement for electrical current. One volt across a resistance of one ohm will produce a flow of one amp.

7  What are volts?—A volt is a measure of electrical pressure differential. A computer power supply usually provides four separate voltages: +12 V, -12 V, +5 V, and -5 V.

7  What is wattage?—Wattage is a measure of the total amount of power that is needed to operate an electrical device.

7  What are ohms?— An ohm is the standard unit of measurement for electrical resistance. Resistors are rated in ohms.