Ohm's Law

State ohms law with graphical representation.

Internal resistance is inversely proportional to the surface area of the electrodes in the electrolyte.

Internal resistance is inversely proportional to electrolyte concentration.

Which are the factors affecting the internal resistance of the cell?

Calculate the area of cross-section of a wire if its length is $1 \mathrm{m}$, its resistance is $23 \mathrm{\Omega }$ and the resistivity of the material is $1.84\times {10}^{-6} \mathrm{\Omega } \mathrm{m}$.

The resistivity of copper is $1.76\times {10}^{-8} \mathrm{ohm} \mathrm{m}$. The radius of the wire is $1 \mathrm{mm}$. Calculate the length of a telegraph wire needed for having a resistance of $10.5 \mathrm{\Omega }$.

A negligibly small current is passed through a wire of length $15 \mathrm{m}$ and of uniform cross-section $6\times {10}^{-7} {\mathrm{m}}^2$ and its resistance is measured to be $5.0 \mathrm{\Omega }$. What is the resistivity of the material at the temperature of the experiment?

Resistance of a metal wire of length $1 \mathrm{m}$ is $26 \mathrm{\Omega }$ at $20°\mathrm{C}$. If the diameter of the wire is $0.3 \mathrm{mm}$, What will be the resistivity of the metal at that temperature?

The resistance of a wire of length $5 \mathrm{m}$ is $100 \mathrm{\Omega }$. If the area of cross-section of the wire is $3\times {10}^{-7} {\mathrm{m}}^2$, calculate the resistivity of the metal.

Distinguish between ohmic and non-ohmic materials.

Semiconductors are examples of ohmic material.

Define ohmic materials and give examples.

What is meant by electrical conductivity?

The electrical resistivity and electrical conductivity of a material is the same.

Explain the relation between electrical resistivity and conductivity?

A material $\mathrm{B}$ has twice the specific resistance of the material $\mathrm{A}$. A circular wire made of $\mathrm{B}$ has twice the diameter of the wire made of $\mathrm{A}$. Then, for the two wires to have to have the same resistance, the ratio $\frac{{\mathrm{L}}_{\mathrm{a}}}{{\mathrm{L}}_{\mathrm{b}}}$ of their respective lengths must be 

If two resistors of $250 \mathrm{\Omega }$ and $150 \mathrm{\Omega }$ are joined together in series and then placed in parallel with a $400 \mathrm{\Omega }$ resistor, the effective resistance of the combination is:

Mathematical representation of Ohm's law is:

The super conductors are used to levitate trains from the track.

Five identical lamps are connected as shown in the figure. Which of the following statement is true?