In a series circuit, if one device fails open, what happens to the circuit?

• A. The other devices continue to operate
• B. The voltage across each device becomes zero
• C. The entire circuit stops current
• D. Current increases

Answer: (C)

In a series circuit there is a single path for current. If one device fails open, that path is broken, so there is no complete circuit for current to flow. With the loop open, the current in the entire circuit drops to zero and nothing in the series circuit operates. The supply voltage ends up across the open gap, not across the functioning devices. That’s why the circuit stops current. The other options don’t fit because a break in a series path stops current everywhere, and the voltage distribution isn’t across each device as if they were all just powered; the break takes the supply voltage.