Circuits Lab 2 & 3

Ohm's Law

Quizlet Link for Lab 2 - Ohm's Law

Before getting supplies to start this lab, you MUST explain how to connect the multimeter to measure current and voltage!!!

Part A Materials:

  • Three D-cells
  • light bulb block
  • six wires
  • multimeter
  • Graph Paper

Measuring Voltage

When measuring the voltage that a resistor or load uses, one probe must be placed on either side of the load.

Measuring Current

When measuring current (I), you must remove a wire and make the meter a part of the circuit (give the electrons one path to flow).

Verifying Ohm's Law

Graphing Empirical Data

Ohmic vs Non-ohmic resistors

Keep in mind, when you are making your graph, that you will be graphing the independent variable (same as manipulated variable) along the x-axis! Every video and graph that we have looked at does NOT do this!!!

In the graph to the left, the blue line is ohmic because the slope is equal to the resistance and is a straight line because V/I always gives you the same resistance.

The green line is Non-Ohmic because the slope is changing! You can NOT use Ohm's Law to calculate the resistance.

Calculating Uncertainty: Percent Error

In the formula above:

T stands for Theoretical Value ... Use Ohm's Law to calculate the Resistance of your bulb for this value

E stands for Experimental Value ... Use the inverse of your slope for this value.

The vertical bars on either side of T-E means that your result will be positive no matter what (even if it comes out negative, change it to a positive value ... this is called absolute value).