Temperature Dependence of Resistivity

A wire has a resistance of $2.5\mathrm{ }\mathrm{\Omega }$ at $28\mathrm{ }{ }^{\mathrm{o}}\mathrm{C}$ and a resistance of $2.9\mathrm{ }\mathrm{\Omega }$ at $100\mathrm{ }{ }^{\mathrm{o}}\mathrm{C}$ . The temperature coefficient of resistance of material of the wire is $2.22\times {10}^{-2} {}^{\mathrm{o}}\mathrm{C}^{-1}$.

A piece of Gold (Au) and Germanium (Ge) are cooled from room temperature to 77 K. Then the resistance of

Find the resistance of the wire at ${30}^{o }C,$ if at $5^{o}C,$ the resistance of same wire is $200\mathrm{\Omega } and at {10}^{o}C,$ the resistance of same wire is $200.2 \mathrm{\Omega }$

Assertion: With increase in temperature, resistance of a conducting wire increases.

Reason: With the increase in temperature, the length and area of cross-section of wire changes but resistivity remains constant.

Assertion: Material used in the construction of a standard resistance is Constantan or Manganin.

Reason: The temperature coefficient the resistances is very small.

Assertion: The drift velocity of electrons in a metallic wire will decrease, if the temperature of the wire is increased.
Reason: On increasing the temperature, conductivity of metallic wire decreases.

Assertion: Resistivity of conductors and semiconductors increase with temperature.

Reason: The electrons move with more kinetic energy and hence relaxation time decreases.

Assertion: With increase in temperature, resistance of a conducting wire increases.
Reason: With the increase in temperature, length and area of cross-section of wire changes, but resistivity remains constant.

Assertion: The temperature dependence of resistance is usually given as $R = R_0 (1 + \alpha ∆t)$. The resistance of a wire changes from $100 \mathrm{\Omega }$ to $150 \mathrm{\Omega }$, when its temperature is increased from $27 °\mathrm{C} \mathrm{to} 227 °\mathrm{C}$. This implies that $\alpha =2.5\times {10}^{-3} °{\mathrm{C}}^{-1}$.

Reason: $R = R_0 (1 + \alpha ∆t)$ is valid only, when the change in the temperature $∆T$ is small and $∆R = (R – R_0)<<R_0$.

Pieces of aluminium (Al) and germanium (Ge) are cooled from $T_{1}K$ to $T_{2}K$. The resistance of

The specific resistance of a conductor increases with,

The junction of a $\mathrm{Ni}-\mathrm{Cu}$ thermocouple are maintained at $0 \mathrm{℃}$ and $100 \mathrm{℃}$. The seebeck emf developed is:

$a_{\mathrm{N}\mathrm{i}-\mathrm{Cu}}=16.3\times {10}^{-6} \mathrm{V} °{\mathrm{C}}^{-1}$

$b_{\mathrm{N}\mathrm{i}-\mathrm{Cu}}=-0.021\times {10}^{-6} \mathrm{V} ° {\mathrm{C}}^{-2}$

With the rise of temperature, the resistivity of a semiconductor

Two different conductors have same resistance at $0^{°}\mathrm{C}$. It is found that the resistance of the first conductor at $t_1°\mathrm{C}$ is equal to the resistance of the second conductor at $t_2°\mathrm{C}$. The ratio of the temperature coefficients of resistance of the conductors,$\frac{{\alpha }_1}{{\alpha }_2}$ is

The thermistors are usually made of

 If the resistance of a conductor is $\text{5 }\mathrm{\Omega }$at $50 °\mathrm{C}$ and $\text{7 }\mathrm{\Omega }$at $100 °\mathrm{C}$, then the mean temperature coefficient of resistance (of the material) is,