Introduction:
Contacts in switches and relays are modeled by low but nonzero ON resistance and extremely high OFF resistance (leakage path). The actual values depend on construction, materials, and environmental factors. This statement tests awareness that these characteristics are not universally identical between device types.
Given Data / Assumptions:
- Manual toggle/pushbutton switches and electromagnetic relays are compared.
- Contact metallurgy, surface finish, and force differ by device.
- Idealized “zero” and “infinite” resistances do not exist in practice.
Concept / Approach:
ON resistance (Ron) is affected by contact pressure, area, and oxidation; OFF resistance (Roff) is limited by insulation/leakage. Different devices and even different part numbers can have markedly different Ron and leakage specifications; thus the statement asserting identity is incorrect.
Step-by-Step Solution:
1) Identify the conductor path and contact interface for each device.2) Note that relay contacts can be optimized for current, voltage, or low-level signals; Ron varies accordingly.3) Recognize that OFF resistance depends on insulation materials and creepage/clearance; these also vary.
Verification / Alternative check:
Review datasheets for representative switches and relays; ON resistance and insulation resistance ranges differ significantly.
Why Other Options Are Wrong:
Correct: Would imply identical values across types, which is not supported.True only for gold-contact relays: Contact plating improves reliability at low levels but does not force equality with manual switches.True only at DC, not AC: The difference exists under both DC and AC conditions, though measurement methods vary.
Common Pitfalls:
Treating the ideal switch model (perfect short/open) as a physical reality.Ignoring environmental effects (oxidation, contamination) on contact resistance.
Final Answer:
Incorrect
Discussion & Comments