Question

The terminal potential difference of a cell is equal to the emf of the cell when:
(A) The cell is an open circuit
(B) The internal resistance of the cell is zero.
(C) The load resistance R is much greater than the internal resistance r.
(D) All are true.

Answer 1

Hint: An Electric cell is the device which converts the chemical energy in the form of the electrical energy. An electric bulb is the device which produces light when the electricity is passed through its terminals.

Complete answer:
The Electric cell was invented by Alessandro Volta who was born on February $ 18,\;{\text{1745}} $ and died on March $ 5,\;{\text{1827}} $
An Electric cell has two terminals which are made up of the metal in which one terminal is positive and the other is negative. When these two terminals are connected to an electrical device, an electric current starts flowing.
In the electric cell, the cell of emf E and the internal resistance r is connected across an external resistance R, then the equation can be expressed between the voltage across R can be expressed as –
 $ V = \dfrac{{ER}}{{R + r}} $
With the increase for “R” then the “V” approaches closer to E and when E is infinite then V reduces to zero.
From the given multiple choices – the option D is the correct answer.

Note:
The first electrical cell was introduced in the year $ 1799 $ which is also known as the voltaic cell. The electric bulb was invented in the year $ 1879 $ which is also known as the light bulb. Know the difference and application of electric cells and electric bulbs. An electric cell is the source of an electricity whereas an electric bulb glows when an electric current is passed through it.