Question

which of the following is a device designed to open an overloaded circuit and prevent overheating?
insulator.
conductor.
resistor.
circuit breaker

Explanation:

An insulator resists the flow of electric current and isn't for opening overloaded circuits. A conductor allows electric current to flow easily and doesn't serve this protective function. A resistor controls the flow of current but not specifically to open an over - loaded circuit. A circuit breaker is designed to open (trip) when a circuit is overloaded, thus preventing overheating.

Answer:

Circuit Breaker