Electrical Resistivity and Conductivity

A physical quantity, associated with electrical conductivity, has the SI unit ohm-meter. Identify this physical quantity.

Two wires of same material and same length have their resistances in the ratio$5: 7$, the ratio of the masses of the wires is

The resistance of mercury _____ as the temperature increases.

Resistance of a wire is $2 \mathrm{\Omega }$. It is drawn in such a way that it experiences a longitudinal strain of $200\%$. Its new resistance is

Ends of two wires $A$ and $B$ having resistivity ${\rho }_{\mathrm{A}}=3\times {10}^{-5} \mathrm{\Omega } \mathrm{m}$ and ${\rho }_{\mathrm{B}}=6\times {10}^{-5} \mathrm{\Omega } \mathrm{m}$ of same cross section area joined in series together to from a single wire. If the resistance of the joined wire does not change with temperature, then find the ratio of their lengths $\frac{l_A}{l_B}$, given that temperature coefficient of resistivity of wire $A$ and $B$ is ${\alpha }_{\mathrm{A}}=4\times {10}^{-5} °{\mathrm{C}}^{-1}$ and ${\alpha }_{\mathrm{B}}=-6\times {10}^{-6} {\mathrm{CC}}^{-1}$. Assume that mechanical dimensions do not change with temperature

A washer is made of metal having resistivity ${10}^{-7} \mathrm{\Omega } \mathrm{m}$. The washer has inner radius $1 \mathrm{cm}$, outer radius $3 \mathrm{cm}$ and thickness $1 \mathrm{mm}$. A magnetic field, oriented normal to the plane of the washer, has the time dependent magnitude $B=\left(2\mathrm{t}\right) \mathrm{tesla} {\sec }^{-1}$. Find the current (in ampere) around the washer

Two rods of copper and iron with the same cross sectional area are joined at $S$ and a steady current $I$ flows through the rods as shown in the figure.

Choose the most appropriate representation of charges accumulated near the junction $S$.

Conductivity of the metal is

Two metal slabs of equal lengths, equal cross sectional areas and having resistances in the ratio $1:2$ are connected first in series and then in parallel separately. The ratio of their effective conductivities is

A cylindrical conductor has a uniform cross-section. The resistivity of its material increases linearly from left end to right end. If a constant current is flowing through it and at a section distance $x$ from left end, the magnitude of electric field intensity is $E$, which of the following graphs is correct?

The product of resistivity and conductivity of a conductor depends on -

What is the length of the wire if the specific resistance of a wire is $\mathrm{\rho }$, volume is $3\mathrm{ }{\mathrm{m}}^3$ and its resistance is $3 \mathrm{\Omega }$.

Wheatstone bridge principle is used to measure the specific resistance $\left(S_1\right)$ of given wire, having length $L$, radius $r$. If $\mathrm{X}$ is the resistance of wire, then specific resistance is : $S_1=X\left(\frac{\pi r^2}{L}\right)$. If the length of the wire gets doubled then the value of specific resistance will be :

Specific resistance of a wire depends on the

In a semiconductor, mobility of electron, i.e. drift velocity per unit applied electric field is $1.6$ ($S.{\rm I}$ unit). Density of electron is ${10}^{19} {\mathrm{m}}^{-3}$ . (Neglect holes concentration). Resistivity of semiconductor is:

Which of the following material has the lowest resistivity?

Two wires of same radius having lengths $l_1$ and $l_2$ and resistivities ${\rho }_1$and ${\rho }_2$ are connected in series. The equivalent resistivity will be

If a wire of certain length is stretched to twice its length, how will its specific resistance change?

Assertion: Insulators do not allow flow of current through themselves.

Reason: They have no free charge carriers.

Assertion: The resistivity of the semiconductor decreases with increase of temperature.

Reason: In a conducting solid, the rate of collision between free electrons and ions increases with increase of temperature.