Which one of the following is correct for an open circuit?A. Vt = 0 ⃝ B. Vt < E ⃝C. Vt = E ⃝ D. Vt = E – Ir

To determine the correct answer for an open circuit, we need to analyze the behavior of voltage in such a scenario. In an open circuit, there is no current flow because the path is broken or open. As a result, the terminal voltage (Vt) across the open sides is equal to the electromotive force (E) of the power source because there is no voltage drop occurring from current flow.

Analysis of Options

1. Option A: $V_t = 0$

   • This option is incorrect because the voltage across the open circuit is not zero; it remains equal to the EMF (E).

2. Option B: $V_t < E$

   • This option is also incorrect because, in an open circuit, the voltage is not less than the EMF. There is no current to cause a voltage drop.

3. Option C: $V_t = E$

   • This option is correct as the terminal voltage equals the electromotive force (E) due to no current flow.

4. Option D: $V_t = E - Ir$

   • This option is incorrect because it considers a load current (I) flowing through a resistance (r), which does not happen in an open circuit.

Final Answer

The correct answer is C. $V_t = E$.