Three conductors are joined as shown in the diagram. The current in conductor RS is $10 \mathrm{A}$. The current in conductor QR is $6 \mathrm{A}$. What will be the current in conductor PR. 

 

Draw the circuit diagram for the following series connection.

Study the electric circuit below. Which of the following switches should be closed so that only two bulbs will light up.

Study the three electric circuits below. Each of them has a glass rod ($G$), a steel rod ($S$), and a wooden rod ($W$). In which of the electric circuits would the bulb not light up.