Wire Resistance and Ohm’s Law PhET MiniLab
Introduction: When an electrical potential exists in a circuit, a current may flow. Current is the flow of electrons in a circuit. Resistance in the circuit slows the flow of the electrons, reducing the current in the circuit. We will use the mathematical form of Ohm’s Law frequently when we investigate electric current and circuits later in this unit.

Additional Material Needed: Clean Drinking Straw

Procedure Part I Wire Resistance: • Blow through the drinking straw. • Cut the drinking straw in half and blow through a half-straw. • Describe the effect of length on ease to blow air through the straw. There is more resistance when the straw is longer. • Cut the halves again in half. • With the four pieces, blow through one, then blow through all four made into a larger, square-shaped straw. • Describe the effect of straw size (diameter) on ease to blow air through the straw. Less resistance • Now, open the PhET Simulation Electricity, Magnets, and Circuits ( Resistance in a Wire[pic]
As wire length (cm) increases, the resistance (Ω) INCREASES
As wire area (cm2) increases, the resistance (Ω) DECREASES
As wire density (Ωcm) increases, the resistance (Ω) STAYS THE SAME
Procedure Part II: Ohm’s Law: Electricity, Magnets, and Circuits ( Ohm’s Law [pic] mA is milliamps, and 1000 milliamps equals one Ampere. • Move the potential (volts) and resistance (ohms) sliders and observe the current (amps)
As voltage increases, current INCREASES
As resistance increases, current DECREASES.
Fill out the tables below and check your work in the simulation. ( ½ pt each ) • Remember, the simulation shows milliamps. • You should show Amperes V = I * R
|8.0 V |.01 A |800 Ω |
|2.0 V |.044 A |.50 Ω