In what respect, does a nearly discharged lead acid secondary cell differ mainly from a freshly charged cell in its emf or in its internal resistance.

Write down the relation between the e.m.f. of a cell and its internal resitance.

What are primary and secondary cell? How do they differ from each other?

On what factor does the internal resistance of a cell depends?

Two cells of emf 2V and 4V and internal resistance 1Omega and 2Omega respectively are connected in parallel so as to send the current in the same direction through an external resistance of 10Omega. Find the potential difference across 10Omega resistor.

A standerd cell emf 1.08 V is balance by the potential difference across 91 cm of a meter long wire applied by a cell of emf 2 V through a series resistor of resistance 2 Omega. The internal resistance of the cell is zero. Find the resistance per unit length of the potentiometer wire.

What is a solar cell ? How does it work ? Write its one use.