Draw a schematic diagram of a circuit consisting of a battery of three cells of 2V each, a $5\Omega $ resistor, and $8\Omega $ resistor, and a $12\Omega $ resistor, and a plug key, all connected in series.

Hint: We are supposed to draw the schematic diagram of a circuit with all the given parts connected in series, which is quite simple. All you have to do is to connect every part using connecting wires and attach them one by one next to each other. Also, make sure that you connect the positive terminal of one cell to the other's negative while forming a battery from the given cells.

Complete step by step answer:
We are asked to draw a schematic diagram of an electric circuit. Let us attempt this question in a step by step manner. Firstly, let us deal with the battery. We are given three cells of 2V each. Remember, we are asked to connect every part in the series, so the negative terminal of one cell is connected to the other's positive terminal to make a series connection and hence form a battery.

The e.m.f of the battery now becomes,
${{\rm{E}}_1} + {{\rm{E}}_2} + {{\rm{E}}_3}\; = \;2{\rm{V + 2V + 2V}}\;{\rm{ = 6V}}$
Here $E_1$, $E_2$, and $E_3$ are e.m.f of the individual cells.

Now, we have the 3 resistors of resistance $5\Omega $, $8\Omega $ and $12\Omega $ respectively. We could connect these resistors one next to the other in series easily. However, as a result of this series connection of resistors, we get the effective resistance in the circuit as their sum.
${\rm{R}}\;{\rm{ = (5 + 8 + 12)}}\Omega \;{\rm{ = }}\;{\rm{25}}\Omega $
Now we can connect the plug key in series with both the battery and the resistors.

This is the schematic diagram of the closed circuit with 3 series resistors, a battery with three cells and a plug key.

Note: Though we are asked to draw a schematic diagram of a very simple circuit, we should approach this in a step by step manner. Always remember that cells are connected with negative terminal of one to positive terminal of other while forming a battery. Now you can simply connect the plug key and the resistors in series with the battery so made.