Question 33Electricity & Electronics - 1st Asst/Chief

The correct answer is D) use of a magnetic trip unit. Molded-case circuit breakers provide protection against short circuits primarily through the use of a magnetic trip unit. The magnetic trip unit is a component within the breaker that senses the flow of electrical current. When a short circuit occurs and the current exceeds a certain threshold, the magnetic trip unit is activated, causing the breaker to open and interrupt the flow of electricity, thereby protecting the circuit from damage. The other options are incorrect because they do not directly address the core function of a molded-case breaker in protecting against short circuits. Shading coils, thermal trip units, and arc quenchers serve different purposes in circuit breaker design and operation.