Which one of the following is correct for an open circuit?
Correct answer: C. Vt = E
- A. Vt=0
- B. Vt < E
- C. Vt = E
- D. Vt = E - Ir
Explanation
In an open circuit, the terminal voltage (Vt) is equal to the source voltage (E). This is because there is no current flow in an open circuit, and hence, no voltage drop across any internal resistance of the source. Therefore, the entire source voltage appears across the open-circuited terminals. So, we have Vt = E in an open circuit.
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About Internal Resistance of Sources
Internal resistance is the opposition to current inside a cell or other source, causing terminal voltage to fall below its emf when current flows. Questions use E = V + Ir, current in complete circuits, lost volts, source combinations, and the difference between internal resistance and the external load resistance.
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