Name _______________
Inquiry Experiment: Battery and Bulb
Question: What are the resistance, voltage, current and power of a circuit with an
LED?
Materials:
 2-3 AA Batteries
 Digital Multimeter (for measuring current and voltage)
 One LED
Procedure:
1. Set up a circuit with two batteries, the digital multimeter, and an LED. Turn the
digital multimeter on. Your LED should light up. Call David over if it’s not.
2. With the LED connected to your power source through the digital multimeter,
(The negative terminal of the battery should go to the black cord of the
multimeter) measure the actual voltage while the bulb is lit (voltage “under
load”). Don’t forget to write the units.
V = _____________
3. Measure the current flowing through the LED. Don’t forget to write the
units.
I = _______________
4. Use Ohm’s Law (V=IR) to calculate the theoretical resistance of the LED with the
batteries connected. Don’t forget to write the units, and show work.
I = _____________
5. Draw a schematic diagram of the circuit you built in step 4. Use the correct
schematic symbols (from your notes packet).
Post – Lab Questions:
6. Use P = IV to calculate the power to the LED.
P = __________ watts
7. Use P = I2R to calculate the power of the LED.
P = __________ watts
8. Use P = V2/R to calculate the power of the LED.
P = __________ watts
Extension:
Go to the website of a battery manufacturer and look up the specifications for a battery
similar to the one you’re using. Using the data from this lab, figure out how long the
battery would be able to power the lightbulb. You will need to find out how many
milliamp-hours or watt-hours the battery can provide. If you have a battery with 10
watt-hours, it can power:



10 watts for 1 hour
1 watt for 10 hours
5 watts for 2 hours