Which of the following has the least resistance

Electrical resistance depends on the material's intrinsic properties. Conductivity is inversely proportional to resistivity, which means materials with high conductivity have low resistance.

In terms of conductivity, the ranking is as follows:

Thus, silver is the best conductor and exhibits the least resistance.

Resistance Comparison

• Wood: High resistance, often used as an insulator.
• Iron: Moderate resistance, higher than silver.
• Rubber: Extremely high resistance, non-conductive material.
• Silver: Lowest resistance due to highest conductivity.

Explanation of a material's intrinsic properties

Intrinsic properties of a material are those characteristics that are inherent to the material itself, regardless of the amount or shape of the material. These properties do not change whether you have a small sample of the material or a large quantity. They are independent of the material's mass or volume and are often used to identify and describe materials.

Common intrinsic properties include:

• Density: The mass per unit volume of a material, typically measured in $\text{kg/m}^3$.

  $$\rho = \frac{m}{V}$$

  where $\rho$ is density, $m$ is mass, and $V$ is volume.

• Melting Point: The temperature at which a solid material transitions to a liquid state.

• Boiling Point: The temperature at which a liquid material transitions to a gaseous state.

• Refractive Index: A measure of how much light is bent when it enters the material.

• Thermal Conductivity: The ability of a material to conduct heat.

  $$q = -k \nabla T$$

  where $q$ is the heat flux, $k$ is the thermal conductivity, and $\nabla T$ is the temperature gradient.

• Electrical Resistivity: How strongly a material opposes the flow of electric current.

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

  where $\rho$ is resistivity, $R$ is resistance, $A$ is the cross-sectional area, and $L$ is the length.

These properties are crucial in material science and engineering because they help in selecting materials for different applications. Knowing a material's intrinsic properties allows scientists and engineers to predict how it will behave under various conditions and in specific applications.

Definition

Electrical conductivity is a measure of a material’s ability to conduct electric current. It quantifies how easily electrons can move through a substance when an electric field is applied.

Units of Measurement

The standard unit of electrical conductivity is the siemens per meter (S/m). A higher siemens value indicates better conductivity.

Mathematical Expression

Electrical conductivity ($\sigma$) can be expressed mathematically as:

Where:

• $\rho$ is the electrical resistivity of the material, measured in ohm-meters ($\Omega \cdot m$).

Factors Affecting Conductivity

Several factors can influence the electrical conductivity of a material:

1. Material composition: Metals like copper and silver have high conductivity, whereas non-metals generally have low conductivity.
2. Temperature: Typically, metals conduct electricity better at lower temperatures, while semiconductors improve in conductivity as the temperature rises.
3. Impurities: The presence of impurities can either increase or decrease conductivity depending on the nature of the impurity and the material.

Applications

Electrical conductivity is crucial in various applications:

• Electronics: For designing circuits and components like resistors, capacitors, and transistors.
• Power transmission: In selecting materials for efficient electricity transmission.
• Industrial processes: Such as electroplating and semiconductor manufacturing.

Conductivity in Different Materials

• Metals: Usually exhibit high electrical conductivity. For example, copper ($\sigma \approx 5.8 \times 10^7 \, S/m$) and aluminum ($\sigma \approx 3.5 \times 10^7 \, S/m$).
• Insulators: Have very low conductivity, such as rubber and glass.
• Semiconductors: Materials like silicon have medium conductivity, and their conductivity can be altered with doping.

Summary

Electrical conductivity is a fundamental property that describes how well a material can conduct an electric current. It's influenced by various factors like material composition, temperature, and impurities, and plays a crucial role in many technological applications. Understanding and manipulating this property is essential for advancements in electronics, power distribution, and industrial processes.