Experiment - 4 :- To identify and understand the function of common fuses, connectors, and switches used in electronics.

Fuses, Connectors, and Switches

Objective: To identify and understand the function of common fuses, connectors, and switches used in electronics.

Equipment:

• Fuses: Glass cartridge, automotive blade, resettable fuse (PTC).

• Connectors: USB-A, RJ45, DC power jack/plug.

• Switches: SPST toggle, SPDT rocker, DPDT slide, pushbutton.

• Tools: Digital multimeter, ruler.

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Procedure

Part 1: Fuses

• Examine: Look at a glass cartridge fuse and an automotive blade fuse. Note the differences in their material and structure.
• Test: Use a multimeter on continuity mode to check each fuse. A good fuse will show continuity.
• Identify: Find the current and voltage ratings printed on the fuses. For the blade fuse, note its color and find its corresponding rating.
• Observe: Measure the resistance of the resettable fuse (PTC) and explain its non-sacrificial function.

Part 2: Connectors

• USB & RJ45: Examine the physical structure of a USB Type-A and an RJ45 connector. Note the number of pins on each.
• Identify: Describe the common use of each connector (e.g., USB for data/power, RJ45 for networking).
• DC Power: Identify the central pin and outer sleeve of a DC power plug/jack. Explain why matching polarity is critical.

Part 3: Switches

• SPST Toggle: Test a toggle switch with a multimeter in continuity mode. Show that it either completes a single circuit or breaks it.
• SPDT Rocker: Identify the three terminals. Use the multimeter to find the common terminal and show how it connects to one of two other terminals depending on the switch position.
• DPDT Slide: Identify the six terminals. Explain that this switch controls two separate circuits. Use the multimeter to map out the connections for both slide positions.
• Pushbutton: Press a pushbutton switch and test its continuity. Determine if it is a momentary (springs back) or latching (stays in place) type.

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Answer the following questions:

What's the key difference in function between a traditional fuse and a resettable fuse?

A traditional fuse is a "sacrificial" component that permanently breaks a circuit when an overcurrent occurs and must be replaced. A resettable fuse (like a PTC thermistor) is non-sacrificial; it temporarily increases its resistance to block current flow and then automatically resets once the overcurrent condition is removed.

Describe the configuration of an SPDT switch and its use.

An SPDT (Single-Pole, Double-Throw) switch has three terminals: one common terminal and two "throws." The switch connects the common terminal to one of the two other terminals at a time. It is used to select between two different circuits or paths with a single input.

If you needed to control two separate circuits with one component, which type of switch would you choose and why?

You would choose a DPDT (Double-Pole, Double-Throw) switch. The "Double-Pole" configuration means it can control two completely separate circuits simultaneously with a single mechanical action.

Why is it important to use the correct type of fuse for a circuit?

Using the correct fuse is crucial for safety. A fuse with too high a current rating will fail to protect the circuit from damage during an overcurrent event, potentially leading to fire or equipment failure. A fuse with too low a rating will blow unnecessarily under normal operating conditions, disrupting the circuit's function.