Materials which easily allow the passage of electric current are known as ______

Question

Examoogle · Accepted Answer

Conductors

Explanation: Conductors are materials that possess a high density of free electrons in their conduction band, allowing charge carriers to move freely through the atomic lattice when an external electric field is applied. This high mobility of electrons results in low electrical resistance, facilitating the easy passage of electric current.

Working Principle: In conductors, the valence band and the conduction band overlap, or the bandgap is negligible. This enables electrons to transition into the conduction band with minimal thermal energy. Under the influence of an electromotive force (EMF), these free electrons drift collectively, creating an electric current represented by the rate of flow of charge $I = \frac{dQ}{dt}$.

Key Formulas: $I = n A v_d q$ — where $n$ is charge carrier density, $A$ is cross-sectional area, $v_d$ is drift velocity, and $q$ is charge.; $R = \rho \frac{l}{A}$ — where $\rho$ is resistivity, $l$ is length, and $A$ is cross-sectional area.

Key Points: Conductors have very low electrical resistivity ($ho$).; Metals like copper, silver, and aluminum are excellent conductors.; The presence of free electrons is the primary requirement for conductivity.; Conductivity is the reciprocal of resistivity: $\sigma = \frac{1}{\rho}$.

Advantages: High efficiency in power transmission.; Low voltage drop across the length of the material.

Disadvantages: Prone to heating due to $I^2 R$ losses.; Susceptible to oxidation and corrosion in specific environments.

Applications: Electrical wiring and power transmission cables.; Printed circuit board (PCB) traces.; Motor windings and transformer coils.

Additional Info: Insulators have high resistivity and no free electrons, preventing current flow.. Dielectrics are insulating materials that can be polarized by an electric field.. Semiconductors have conductivities between those of conductors and insulators, usually controlled by doping.

Answer: B is correct — Conductors provide a low-resistance path for the movement of free electrons, enabling the flow of electric current.

Exam Tip: Remember that in metallic conductors, temperature rise increases atomic vibration, which leads to higher resistance; always check the temperature coefficient of the material.

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