Measuring Resistance
Purpose:
You will learn how to measure resistance across a resistor
You will build circuits using variable and fixed resistors.
You will measure current when resistance is changed.
You will learn how to measure resistance across a resistor
You will build circuits using variable and fixed resistors.
You will measure current when resistance is changed.
Materials: Multimeter, bulbs, bulb holder, wires, battery, fixed resistors, potentiometer
Procedure: Part 1:
- Find the bag with the resistors.
- Create a table to measure the resistance of the different resistors. To identify them, mark down the colored bands on each resistor.
- To measure resistance, place the red wire in the OHM port and the black wire in the COM port, and point the dial at the OHM. Put the black lead on one side of the resistor and the red lead on the other. Record the value in your data table.
- Record the resistance for each resistor in your bag. (There are six).
Procedure: Part 2:
- Build a circuit with the battery, bulb and bulb holder, a switch, and your variable resistor. A variable resistor is called a potentiometer, and it's similar to a dimmer switch. (Should have a knob on it!)
- Turn the potentiometer all the way to one side (as though it was all the way off). Your bulb should have a tiny bit of light! This is Setting #1.
- Measure the current (refer to previous lab if you can't remember how to set up the multimeter) at point indicated in the diagram and record the value.
- Turn the circuit off (open the switch) and measure resistance from one side of the dimmer switch to the other. BE CAREFUL NOT TO TOUCH THE KNOB. To measure resistance, place the red wire in the OHM port and the black wire in the COM port, and point the dial at the OHM. Record the value in your data table.
- Adjust the dimmer switch (potentiometer) so the light bulb is a tiny bit brighter and repeat steps 3 & 4. Continue until you have FIVE settings for the potentiometer.
Analysis:
- Look at your values for current and resistance. What observations can you make about the relationship between current and resistance? Use your data to support your observations.