What would an indication of voltage drop across a closed switch suggest?

• A. The circuit is overloaded or the contacts of the switch may be dirty.
• B. The circuit is functioning normally.
• C. The supply is disconnected.
• D. The load is shorted.

Answer: (A)

When a switch is closed, it should act like a near-perfect conductor, so the voltage across it is essentially zero. If you measure a noticeable voltage drop across a closed switch, it means the switch isn’t conducting as well as it should—the contact resistance is high under load. This typically happens because the contacts are dirty or oxidized, or the switch is carrying more current than it was designed to handle, causing heating and increased resistance. In short, a voltage drop across a closed switch signals either dirty/ worn contacts or an overload condition, not normal operation.