The question asks for a characteristic of a slow-blow fuse. We need to understand the fundamental difference between slow-blow and fast-blow fuses, particularly their response to overcurrent conditions.
B) It has a delayed response to short-term overcurrent — This accurately describes a slow-blow fuse. It is designed to tolerate temporary current surges (like inrush current when a motor starts) for a short period before blowing, thus preventing unnecessary circuit interruption.
The question asks to identify a type of fuse that is designed to be reusable. We need to evaluate each option based on its operational principle and whether it can be reset or reused after tripping due to an overcurrent.
Correct Option: C) Resettable PTC fuse — This type of fuse is specifically designed to be reusable. It uses a polymer that increases its resistance significantly when heated by overcurrent, effectively breaking the circuit. Once the fault is cleared and the polymer cools, its resistance drops, and it resets, allowing current to flow again without needing replacement.
The question asks about the primary use of a High-Rupturing Capacity (HRC) fuse. Understanding the characteristics and purpose of HRC fuses is key to identifying their main application area.
B) In high-voltage and high-current applications. HRC fuses are specifically designed to safely clear very large fault currents that can occur in high-voltage and high-current systems, such as industrial installations, power distribution networks, and substations. Their robust construction and arc-quenching capabilities make them ideal for protecting equipment in these demanding environments.
The question asks to identify a specific type of fuse commonly found in older electrical installations and characterized by its screw-in design. We need to evaluate each option based on its typical application and physical characteristics.
C) Edison-base fuse is the correct answer. These fuses are characterized by their screw-in design, resembling the base of an incandescent light bulb, and were widely used in older residential and commercial electrical systems as a primary circuit protection device.
The question asks about the correct placement of a fuse in an electrical circuit. A fuse is a safety device designed to protect an electrical circuit from overcurrent. Its primary function is to break the circuit when the current exceeds a safe limit, thus preventing damage to appliances and reducing the risk of fire or electric shock. To effectively perform this function, the fuse must be placed in a way that all the current flowing to the load passes through it.
B) In series with the load — Placing the fuse in series with the load ensures that all the current flowing to the load passes through the fuse. When an overcurrent occurs, the fuse element melts, breaking the circuit and protecting the load and wiring from damage.
The question asks about the essential safety precaution to take before replacing a blown fuse. This involves understanding basic electrical safety principles.
Correct Option: B) Ensure the power is off. This is a fundamental electrical safety rule. Before working on any electrical component, especially one that has failed due to an electrical fault (like a blown fuse), it is crucial to disconnect the power supply to prevent electric shock.