To solve the problem, we need to analyze the behavior of the current in a series connection of resistors when one resistor breaks down.
1. Series Connection of Resistors:
In a series circuit, the total resistance \( R_{\text{total}} \) is the sum of the individual resistances. The current \( I \) in the circuit is the same through all resistors and is given by Ohm's law:
\[
I = \frac{V}{R_{\text{total}}}
\]
where \( V \) is the total voltage and \( R_{\text{total}} \) is the sum of the resistances in the series.
2. Effect of One Resistor Breaking Down:
If one of the resistors in a series circuit breaks down (becomes an open circuit), it creates a break in the circuit. As a result, the total resistance becomes infinite, and the current in the circuit will drop to zero, because there is no continuous path for the current to flow.
3. Conclusion:
If one resistor breaks down in a series connection, the circuit becomes open, and no current flows through the circuit.
Final Answer:
The correct answer is (1) circuit is open and no current flows in the circuit.