Lab Activity: Basic Circuit Analysis
There are two parts to this activity. The first is a hands-on investigataion with simple lightbulb circuits. The second is a video lab activity. Both activities will help you to learn how to analyze simple electrical circuits. Your lab report should include both parts of this investigation.
Part 1: Lightbulb Circuits
Goal: By connecting the bulbs and batteries in a wide variety of ways, draw several conclusions about how the brightness (power) of the bulbs are affected by how they are connected to each other and to the batteries.
Type of Activity: Guided Inquiry
Materials Needed: Two AA batteries (1.5 volt, Alkaline), Two AA battery holders (or a battery holder that connects two AA batteries),
a 10 pack of 14 inch jumper wires with alligator clip ends(any copper wire will do, but without alligator clips the circuit connections are difficult to maintain), 4 light bulbs (#14 round bulbs), 4 bulb holders
These materials can be purchased at myscience-prep.com.
Notes: The connection points on the bulb holder are shown below. Also, be sure to connect the battery poles as shown (+ to -).
Activity:
In this lab you will investigate the effect of various circuit designs on the brightness of light bulbs. You learned in the previous presentations that current, voltage, resistance and power are important electrical properties. Incandescent light bulbs are made of resistors (filaments) that can give off heat and light when conducting electrical current. The rate at which the bulb gives off heat and light is power (P = IV = I2R = V2/R). The “brightness” of a bulb can thus be used as a rough measure of the power dissipated by the bulb. For light bulbs of the type you will be using in this lab a minimum voltage is required before the light bulb will be bright enough for a human to see. IMPORTANT: If the resistance of all the bulbs are the same (you can assume that in this activity), then the brightness can also be used to give a rough measure of voltage (P = V2/R) for each bulb.
Use the equipment to create the circuits shown below. Make observations about the brightness of each bulb in each circuit (and how the brightnesses compare from circuit to circuit. You can use the brightness of the single bulb in circuit #1 as a "reference" brightness. In other words, you can compare other brightnesses to it.). Record these observations in table form. Be sure to include a digital image of each circuit for the lab report in the apparatus section of the report.
Once you have completed the work and made your observations, answer the questions below. Assume that all the bulbs have the same resistance. Base your answers on your observations and the forms of Joule's Law that you already learned:
P = IV = I2R = V2/R
1. Which bulbs (in the circuits you constructed) have the greatest voltage? Which have the lowest voltage? Explain your response.
2. How do the voltages of the bulbs in circuit #3 compare to the voltages in circuit #2? Explain your observation using concepts from the presentations.
3. How do the voltages of the bulbs in circuit #5 compare to the voltages of the bulbs in circuit #6? Explain your observation using concepts from the presentations.
4. How do the brightnesses of the bulbs in circuit #3 compare to those in circuit #6? Explain your observation using concepts from the presentations.
5. In the previous practice problem set, you learned that resistivity is affected by temperature. How do you think the observations in this lab could be affected by that fact? Explain your response.
Click here to compare your observations and answers to those typically found.
Part 2: Using Meters to Verify Ohm's Law
Goal: To learn how to use a multimeter and make calculations with Ohm's Law using the multimeter measurements.
Type of Activity: Structured Inquiry
Materials Needed: Video lab
Activity:
The video below will allow you to take measurements on two simple circuits using a multimeter. This device can be switched between various modes. In this lab we will use it to make voltage measurements (in voltmeter mode) and current measurements (in ammeter mode). You will need to make careful observations of the circuit analysis in the video. When you are ready to start, play the video and follow the instructions given. Use your lab notebook to record all your work.
This video lab is approximately 14 minutes in length.