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Three materials A, B and C have electric...

Three materials A, B and C have electrical conductivities `sigma , 2 sigma` and `2 sigma` respectively. Their numbers densities of free electrons are 2 n, n and 2n respectively. For which material is a average collision time of free electrons maximum?

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To determine which material has the maximum average collision time (relaxation time) of free electrons, we can use the relationship between electrical conductivity (σ), number density of free electrons (n), and average collision time (τ). ### Step-by-Step Solution: 1. **Understand the relationship**: The electrical conductivity (σ) of a material is given by the formula: \[ \sigma = \frac{n e^2 \tau}{m} \] ...
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Knowledge Check

  • Electrical conductivies of Ge and Na are sigma_(1) and sigma_(2) respectively. If these substances are heard, then

    A
    `sigma_(1)` decreases and `sigma_(2)` increases
    B
    both `sigma_(1)` and `sigma_(2)` decreases
    C
    both `sigma_(1)` and `sigma_(2)` increases
    D
    `sigma_(1)` increases and `sigma_(2)` decreases

  • sigma_(1) and sigma_(2) are the electrical conductivities of Ge and Na respectively. If these substances are heated, then

    A
    Both `sigma_(1)` and `sigma_(2)` increase
    B
    `sigma_(1)` increases and `sigma_(2)` decrease
    C
    `sigma_(1)` decreases and `sigma_(2)` increases
    D
    Both `sigma_(1)` and `sigma_(2)` decrease

  • Three non-conducting large parallel plates have surface charge densities sigma, -2 sigma and 4 sigma respectively as shown in the figure. The electric field at the point P is

    A
    `(sigma)/(epsilon_0)`
    B
    `(sigma)/(2 epsilon_0)`
    C
    `(3 sigma)/(2epsilon_0)`
    D
    `(3sigma)/(epsilon_0)`