Change in Electric Current: Physics Lab

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  • 0:03 What is a Resistor?
  • 0:49 Physics Lab Steps
  • 1:35 Data Analysis
  • 2:39 Lesson Summary
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Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

After completing this lab, you will be able to explain what electric current is, and how it is affected by resistors in a circuit. You can also take a short quiz to test your knowledge.

What is a Resistor?

An electric circuit is a complete loop in which electrons from a voltage or current source flow. You can think of it like water flowing around a water-slide - the battery is the pump that sends it to the top of the hill. The flow of the water can be measured, and in a circuit, the flow of charge can also be measured. The current in a circuit is the rate of flow of charge through the circuit, measured in amps.

Any component you put in a circuit, from bulbs, to sensors, to motors, all act as resistors. A resistor is a component that resists the flow of charge in a circuit. It's as if they take energy from the circuit and use that to perform their function. Today, we're going to investigate how resistors affect the current (the flow of charge) in a circuit.

Physics Lab Steps

For this physics lab, you will need:

  • A battery
  • Three small bulbs
  • Five wires
  • And, an ammeter (device that measures current flowing through it)

Step 1: Use the wires to connect the battery, the ammeter and one of the bulbs in one complete loop (connected in 'series').

Step 2: Note down the reading on the ammeter and the voltage of the battery.

Step 3: Add an extra bulb into the circuit loop.

Step 4: Note down the reading on the ammeter.

Step 5: Add a third and final bulb into the circuit loop.

Step 6: Note down the reading on the ammeter.

You can collect your data in a table. If you haven't already, now is the time to pause the video and complete the lab. Good luck!

Data Analysis

Now that you've collected your data, it's time to analyze it. The first circuit, with just one bulb connected, had a particular current. You also measured the voltage. Resistance is defined mathematically as voltage divided by current. So, if you take your voltage and divide it by your current, you'll get the resistance of the circuit. Since there's only one bulb, this is approximately the same as the resistance of the bulb.

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