Question

If the identical cells each having an emf of 20 V are connected in Parallel, then the emf of the combinations is
A. 2V
B. 200V
C. 20V
D. 10V

Answer 1

Hint: We need to understand the idea of "Cells" before we can begin this question. Chemical energy is transformed into electrical energy within the cell. The two types of cells, primary and secondary cells.

Complete step by step solution:
Cells in series: Cells are said to be arranged in a series if they are all connected end to end so that the positive terminal of one cell is connected to the negative terminal of the cell after it. The equivalent emf of cells arranged in series is provided as, ${{E}_{eq}}={{E}_{1}}+{{E}_{2}}+{{E}_{3}}+.......+{{E}_{n}}$
The following equation describes the equivalent internal resistance of cells arranged in a series:
${{r}_{eq}}={{r}_{1}}+{{r}_{2}}+{{r}_{3}}+.....+{{r}_{n}}$

Cells in parallel: A parallel arrangement of cells is when a group of cells are connected so that their positive terminals are connected at one location and their negative terminals are connected at another one. The following is the comparable emf of cells arranged in parallel:
${{E}_{eq}}=\dfrac{{{E}_{1}}/{{r}_{1}}+{{E}_{2}}/{{r}_{2}}+{{E}_{3}}/{{r}_{3}}+.....+{{E}_{n}}/{{r}_{n}}}{1/{{r}_{1}}+1/{{r}_{2}}+1/{{r}_{3}}.....+1/{{r}_{n}}}$
The following is the equivalent internal resistance of cells arranged in parallel:
$\dfrac{1}{{{r}_{eq}}}=\dfrac{1}{{{r}_{1}}}+\dfrac{1}{{{r}_{2}}}+\dfrac{1}{{{r}_{3}}}+.......+\dfrac{1}{{{r}_{n}}}$

Given: E = 20 V
Potential difference across terminals is the same for all every cell.
Therefore, Emf of combination = emf of cell = 20 V

Hence, option C is correct.

Note: Primary cells cannot be recharged and must be discarded after their lifespan expires, whereas secondary cells must be replenished when their charge runs out. Both types of batteries are widely used in many gadgets, and the size and substance used in them varies.