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Physical Science

Learners will observe how resistance is affected by a conductor’s material, length, and cross-sectional area.

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After completing this tutorial, you will be able to complete the following:

- Explain that a conductor’s resistance is proportional to its length.
- Explain that a conductor’s resistance is inversely proportional to its cross-sectional area.
- Explain that some wires of the same length and cross-sectional area may differ in resistance due to the metal they are made from.

An electrical conductor is a material that can move an electrical charge from one point to another. All metal conductors, such as wire, contain an electrical charge in the form of electrons that exist as part of the metal.

Ohm's Law defines the relationships between resistance, voltage and current. It states that the current between two points along a conductor is directly proportional to the voltage and inversely proportional to the resistance. There are three equations for Ohm's Law that are used interchangeably.

Resistance = Voltage/Current Voltage = Current*Resistance Current = Voltage/Resistance

Resistance, or resistivity, is the impedance of electrical current traveling through a conductor. Voltage is the electrical potential difference between two points connected by a conductor. It is measured in volts (V). An ampere, or "amp", is the unit of measurement used to measure an electrical charge, or constant current flowing through a conductor at a specific point over a period of time.

To calculate any one variable, you must know the other two variables. By using a power supply set to a certain voltage, and an ammeter to measure the current passed through a conductor by the power supply, you can calculate the resistance of the conductor being analyzed. By altering the characteristics of the conductor, such as the length or the cross-sectional area, you can affect the resistance of the conductor.

By increasing the length of a conductor, while all other variables remain the same, the resistance increases because the current travels further from one point along the conductor to the other. Conversely, decreasing the length of the conductor decreases the resistance encountered. This is a directly proportional relationship. Similarly, increasing the cross-sectional area of a conductor, with all other variables remaining the same, will decrease the resistance that a current encounters as it travels from one point to another along the conductor. Whereas, decreasing the cross-sectional area increases the resistance encountered because current has a restricted area through which to flow. This demonstrates an inversely proportional relationship.

Approximate Time | 20 Minutes |

Pre-requisite Concepts | conductors, insulators |

Course | Physical Science |

Type of Tutorial | Experiment |

Key Vocabulary | 3D, anmeter, conductor |