1. In applying the superposition theorem, (a) all sources are considered simultaneously (b) all voltage sources are considered simultaneously (c) the sources are considered one at a time with all others replaced by a short (d) the sources are considered one at a time with all others replaced by their internal impedances

D - the sources are considered one at a time with all others replaced by their internal impedances

Explanation:

Superposition Theorem: The superposition theorem states that in a linear circuit with several sources, the current and voltage for any element in the circuit is the sum of the currents and voltages produced by each source acting independently.

In applying the superposition theorem:

D. the sources are considered one at a time with all others replaced by their internal impedance.

Explanation:

Superposition Theorem:

According to this theorem, in a linear electrical circuit with more than one power sources, the current or voltage in any branch of circuit is equal to the sum of currents or voltages produced by the each power source independently while other are replaced by their internal impedance.

According to this theorem, we replace all the voltage sources by short circuit while current sources are replaced by the open circuit. This theorem is applicable for linear circuitry and only for current and voltage.