Resistivity of Metals, Semiconductors, and Insulators

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What is the relationship between current and potential difference according to Ohm's law?

Current flowing through a conductor is directly proportional to the potential difference.

How is resistance calculated using the V-I graph?

Resistance is determined by comparing the slopes of V-I graphs of different materials.

Define conductance and its unit.

Conductance is the reciprocal of resistance. Its unit is siemens (S) or mho.

What are the factors that affect the resistance of a conductor?

The material, length, and cross-sectional area of the conductor. Signup and view all the answers

Explain resistivity of a conductor and state its unit.

Resistivity is the property that relates resistance to the material. Its unit is ohm-meter (Ωm). Signup and view all the answers

How does the resistivity of a material change when a conductor is stretched to double its length?

The resistivity of the material remains unchanged. Signup and view all the answers

Define internal resistance of a cell.

Resistance offered by the electrolytes to the flow of current through it. Signup and view all the answers

What is the relation connecting emf and terminal potential difference?

V = ε – Ir Signup and view all the answers

Differentiate between emf and terminal voltage of a cell.

Emf is the potential difference in an open circuit, while terminal voltage is in a closed circuit. Signup and view all the answers

Why are Nichrome, Constantan, and Manganin used as standard resistors?

Their resistivity does not vary considerably with temperature. Signup and view all the answers

What happens to the resistivity of semiconductors and insulators with temperature?

It decreases. Signup and view all the answers

In a circuit with a 10V emf and 3Ω internal resistance, if the current is 0.5A, what is the external resistance value?

14Ω Signup and view all the answers

Define conductivity.

Conductivity is the reciprocal of resistivity. Signup and view all the answers

Write Ohm's law in vector form.

$\mathbf{j} = \sigma \mathbf{E}$ Signup and view all the answers

What are the limitations of Ohm’s Law?

Some materials and devices used in electric circuits do not obey Ohm’s law and are called Non-Ohmic conductors. V-I graphs of non-ohmic conductors are not linear. Signup and view all the answers

Differentiate Ohmic and non-ohmic Conductors.

Ohmic conductors obey Ohm’s law, have a linear Voltage-Current graph, and include metals like Nichrome. Non-ohmic conductors do not obey Ohm’s law, have non-linear V-I graphs, and include materials like semiconductors, diodes, and transistors. Signup and view all the answers

Write the expression for temperature co-efficient of resistivity. Write its unit and dimension.

$\rho_T = \rho_0 [1 + \alpha(T - T_0)]$, where $\alpha = (T - T_0)\frac{\rho_0}{\rho}$ is the temperature co-efficient of resistivity. The unit of $\alpha$ is $K^{-1}$ and its dimension is $[Temperature]^{-1}$. Signup and view all the answers

How does the resistivity of metals vary with temperature?

The resistivity of metals increases with temperature. This increase is described by the temperature co-efficient of resistivity, $\alpha$, which is positive for metals. Signup and view all the answers