Correct Option
The correct option isThe electric circuit is incomplete.
Explanation
For an electric current to flow and energize a device such as a bulb, there must be a continuous, unbroken conducting path connecting the terminals of the power source. This continuous path is known as a closed circuit.
Option Analysis
- The potential difference becomes zero. is Incorrect: The potential difference (voltage) is maintained by the power source regardless of the circuit's state. Even with a broken filament, the potential difference exists across the break, but current cannot flow to utilize it.
- The resistance of the circuit becomes infinite. is Incorrect: While an open circuit effectively has infinite resistance, the primary physical reason for the failure to glow is the lack of continuity in the conducting path. "Infinite resistance" is a mathematical consequence of the gap, whereas the "incomplete circuit" describes the structural cause.
- The electric circuit is incomplete. is Correct: A broken filament creates a physical gap in the wire, resulting in an open circuit or incomplete circuit. Without a complete loop, charge carriers (electrons) cannot circulate, and no electrical energy is converted into light and heat.
- The power source is short-circuited. is Incorrect: A short circuit implies a path of near-zero resistance that bypasses the load, causing excessive current flow. A broken filament creates a break (infinite resistance), which is the opposite condition of a short circuit.
Key Takeaway: An electric bulb requires a closed circuit to function. A broken filament breaks the continuity of the path, creating an open circuit and preventing current flow.