Ohm's Law, Resistivity & Circuitry

Understanding Ohm's Law

Ohm's Law is a fundamental principle in physics that describes the relationship between voltage, current, and resistance in an electrical circuit. It is expressed by the formula:

$$V = IR$$

• V is the potential difference (voltage) measured in volts (V).
• I is the current measured in amperes (A).
• R is the resistance measured in ohms (Ω).

Verifying Ohm's Law

To verify Ohm's Law, you can set up a simple circuit with a known resistor and measure the voltage across it and the current flowing through it. By calculating $R = \frac{V}{I}$, you should find the resistance matches the known value.

Resistivity and Conductivity

Resistivity is a measure of how strongly a material opposes the flow of electric current. It is denoted by $\rho$ and measured in ohm-meters (Ω·m). Conductivity is the inverse of resistivity and measures how easily a material allows the flow of electric current.

The resistance $R$ of a wire is related to its resistivity by:

$$R = \rho \frac{L}{A}$$

• $\rho$ is the resistivity of the material.
• L is the length of the wire.
• A is the cross-sectional area of the wire.

Factors Affecting Resistance

• Material: Different materials have different resistivities.
• Length: Longer wires have more resistance.
• Cross-sectional area: Thicker wires have less resistance.
• Temperature: Resistance typically increases with temperature.