Internal Resistance of a Cell

Define the terms electric energy and electric power. Give their units.

Name any one material having a small value of temperature coefficient of resistance. Write one use of this material.

Two cells of emf ${\epsilon }_1$ and ${\epsilon }_2$ and internal resistances $r_1$ and $r_2$ respectively are connected in parallel. Obtain expressions for the equivalent emf of the combination.
Write the corresponding formulae for the series combination.

Two cells of emf ${\epsilon }_1$ and ${\epsilon }_2$ and internal resistances $r_1$ and $r_2$ respectively are connected in parallel. Obtain expressions for the equivalent
(i) resistance. Write the corresponding formulae for the series combination.

Two identical cells, each of emf $\epsilon$ and internal resistance $r$ are connected in parallel to an external resistance $R.$ Find the expression for the total current flowing in the circuit.

A cell of emf $\xi$ and internal resistance $r$ is connected across a variable resistance $R.$ Plot graphs showing the variation of terminal p.d. $V$ with $R.$ Predict from the second graph under which $V$ becomes equal to $\xi .$

A cell of emf $\xi$ and internal resistance $r$ is connected across a variable resistance $R.$ Plot graphs showing the variation of (i) $E \text{and }R.$ Predict from the second graph under which $V$ becomes equal to $\xi .$

Distinguish between emf ($\xi$) and terminal voltage $\left(V\right)$ of a cell having internal resistance$\text{'}r\text{'}.$ Draw a plot showing the variation of terminal voltage $\left(V\right)$ vs the current $\left(I\right)$ drawn from the cell. Using this plot, how does one determine the emf and the internal resistance of the cell ?

A cell of emf  $\text{'}\xi \text{'}$ and internal resistance $\text{'}r\text{'}$ is connected across a variable load resistor $R.$ Draw the plots of the terminal voltage $V$ versus  the current $I.$

A cell of emf  $\text{'}\xi \text{'}$ and internal resistance $\text{'}r\text{'}$ is connected across a variable load resistor $R.$ Draw the plots of the terminal voltage $V$ versus (i) $R$

How much is the resistance of a closed plug-key ?

How much is the resistance of an air-gap ?

A series battery of $6$ lead accumulators, each of emf $2.0 \mathrm{V}$ and internal resistance $0.25 \mathrm{\Omega }$ is charged by a $230 \mathrm{V}$ d.c. mains. To limit the charging current, a series resistance of $53 \mathrm{\Omega }$ is used in the charging circuit. What is power dissipated as heat? Account for the difference in the two cases.

Answer the following:

Why are the connections between the resistors in a metre bridge made of thick copper strips?

Explain, giving reasons, how the internal resistance of a cell changes in the following cases:

When temperature of the electrolyte is increased.

Explain, giving reasons, how the internal resistance of a cell changes in the following case:

When area of the anode is decreased.

Explain, giving reasons, how the internal resistance of a cell changes in the following case:

When concentration of the electrolyte is increased.

A car battery has an emf of $12 \mathrm{V}$. Eight ordinary cells connected in series can also supply $12 \mathrm{V}$. But we do not use such an arrangement of cells in the car. Why?

You are given a primary and a secondary cell of the same emf. From which cell will you be able to draw larger current and why?

Plot a graph showing the variation of current '$I$' versus resistance '$R$', connected to a cell of emf $\epsilon$ and internal resistance '$r$'.