Considering the construction and typical use of a rheostat (a variable resistor used as a 2-terminal adjustable resistance), how many external connections does it normally employ?

Introduction / Context:
A rheostat is a variable resistor commonly used to adjust current or set a coarse resistance in power applications. Although many potentiometers have three terminals, a rheostat is used with only two to create an adjustable series resistance.

Given Data / Assumptions:

• Typical device has three terminals physically: two end terminals of the resistive element and a wiper.
• Rheostat connection convention uses the wiper and one end terminal.
• Goal: number of connections in normal rheostat usage.

Concept / Approach:
Using the wiper and one end gives a variable resistance equal to the portion of the track between them. The unused terminal is left floating (or sometimes tied to wiper for noise reduction, but still two external connections are functionally used). Hence, operationally, the rheostat is a two-terminal element.

Step-by-Step Solution:
Identify terminals: end A, wiper, end B.Choose wiper + one end (A or B) to form the rheostat connections.As the wiper moves, resistance changes from near 0 up to the full track resistance.Therefore, the normal count of connections used is 2.

Verification / Alternative check:
Datasheets often describe potentiometer usage modes: as voltage divider (3-terminal) or as rheostat (2-terminal). The latter confirms the expected answer.

Why Other Options Are Wrong:

• 1: A single connection cannot form a complete path.
• 3 or 4: Three terminals are for potentiometer divider mode; rheostat operation uses two.

Common Pitfalls:

• Assuming all potentiometers are always used with three terminals.
• Confusing physical terminal count with the connected terminal count in a given application.

Final Answer:
2