Protection Devices Flashcards

What happens when current flows uncontrolled through a wire due to a short circuit?

The wire becomes overheated, the insulation can smoke and burn, and the wire may melt.

What is a fuse in an electrical circuit?

A fuse is a small section of electrical conductor designed to melt and open the circuit when too much current is pulled through it.

What must be done after a fuse has blown?

A new fuse must be installed after the problem causing the excessive electrical flow is corrected.

How are modern fuses rated?

Modern fuses are rated in amps, commonly at 15, 20, 30, etc.

What is a circuit breaker?

A device that interrupts the flow of current in a circuit when it exceeds a predetermined level.

What is the design of a typical thermal circuit breaker?

It has coil windings wrapped around an iron core connected to a bimetal blade.

How does a bimetal arm in a circuit breaker function?

It curls up against magnetic pull when overheated, opening the circuit.

What is a fusible link?

A section of wire designed to protect a circuit from high currents, functioning similarly to fuses.

How is a fusible link typically sized?

It is usually two gauge sizes smaller than the wiring it protects.

How can you identify a fusible link?

By its colored insulation which indicates maximum circuit protection available.

What is the purpose of switches in electrical circuits?

To open or close a circuit on demand, controlling the flow of current.

What is the simplest type of switch?

A manual knife-blade assembly.

What type of switch incorporates a circuit breaker for headlight protection?

A headlight switch.

What is a double-throw switch?

A switch that allows power to be directed in one of two directions depending on its position.

What is a relay?

A remotely operated magnetic mechanical switch that allows a low control current to switch on higher amperage circuits.

What is a diode?

A semiconductor that allows electricity to flow in only one direction, functioning like an electrical check valve.

What is the purpose of a soldering flux?

To clean the metal, prepare it for soldering, and enable solder to spread.

What materials are necessary for successful soldering?

Proper flux, good solder, and sufficient heat.

What happens if solder is melted directly on the soldering iron?

It can destroy the effectiveness of the flux.

What should be used as a heat sink when soldering heat-sensitive components?

An alligator clip or needle-nose pliers.

What type of solder should be used for electrical connections?

Solder that is labeled as 'rosin core'.

What is the range of temperatures at which solder typically melts?

Between 360 and 460°F.

What is the primary danger of using incorrect current in a relay?

It can allow too much current to flow through the driver, potentially leading to module replacement.

What can indicate a damaged fusible link?

Discoloration or misshaping of the link.

What component works on the principle of different thermal expansion rates?

The bimetal arm in a circuit breaker.

When should repairs be made to wiring harnesses rather than individual wires?

When specified in the manufacturer’s recommendations, especially for critical systems like SRS.

What is the advantage of soldered connections compared to crimped connections?

Soldered connections are more secure and have better electrical conductivity.

Why should care be taken when stripping wire insulation?

To avoid cutting wire strands and damaging the wire.

What color coding on fusible links indicates?

The amount of maximum circuit protection available.

Why are some switches not hard wired to the circuit they control?

They may function as input sensors to an electronic module.

What happens when a mercury switch detects motion?

The mercury completes the circuit for the light when the lid is raised.

Why should a diodes various resistance readings be checked?

To ensure it only conducts electricity in one direction.

Where is excessive heat most dangerous during soldering?

On heat-sensitive components during repairs.

What can excessive heat during soldering cause on a circuit board?

It can lift the printed circuit from the board, rendering it useless.

How can wiring problems be further diagnosed?

By checking for voltage drop while current is applied.

What is the function of a relay’s control coil?

To control the on and off state of higher amperage circuits.

What can happen if the wrong relay is used in a circuit?

It can cause permanent damage to the control module's circuit board.

What are the wavelengths of diodes used in various applications?

Light-emitting diodes (LEDs) produce specific colors like red, yellow, and green used in indicators.

What is a common symptom indicating wiring failure?

Damaged insulation, fraying, or corrosion on wires.

Why is a soldering gun recommended for heavy use?

Because it delivers higher temperatures and recovers heat faster for larger wires.

What does a fuse do when it reaches its maximum current-carrying capability?

It melts, opening the circuit to stop excessive current flow.

What occurs when the bimetal element in a temperature-sensitive switch is heated?

It bends away from the hotter metal, opening or closing the circuit.