Correct Option
The correct option isElectric fuse
Explanation
The operation of safety devices in electrical circuits often relies on the heating effect of electric current (Joule’s Heating). According to this principle, when an electric current flows through a conductor, heat is generated proportional to the square of the current ($H \propto I^2$). This thermal energy can be utilized to break a circuit physically if the current exceeds safe limits.
Option Analysis
- Electric cell Electric cell: Incorrect. An electric cell is a source of electromotive force (EMF) that converts chemical energy into electrical energy to maintain current in a circuit. It is not a safety mechanism.
- Electric fuse Electric fuse: Correct. An electric fuse is a safety device consisting of a wire made from a material with a low melting point (such as an alloy of lead and tin). If the current in the circuit rises abruptly (due to a short circuit or overloading), the heat generated melts the fuse wire. This breaks the circuit, preventing damage to appliances and avoiding fire hazards.
- Electromagnet: Incorrect. An electromagnet utilizes the magnetic effect of electric current to generate a magnetic field. It is used in devices like motors, generators, and relays, not primarily as a thermal safety break.
- Electric bell Electric bell: Incorrect. An electric bell operates on the magnetic effect of electric current. It uses an electromagnet to attract an armature that strikes a gong.
Key Takeaway: The electric fuse works on the principle of the heating effect of electric current. It protects circuits by melting and breaking the connection when the current exceeds a specific safety rating.