Series aiding/opposing sources (algebraic sum): Three DC sources of −1.2 V, +15 V, and −6 V are connected in series. What is the magnitude of the total resultant voltage?

Introduction / Context:
When DC sources are connected in series, their voltages add algebraically, taking polarity into account. Aiding sources add; opposing sources subtract. The final question often asks either for signed result or its magnitude. Here, the magnitude is requested.

Given Data / Assumptions:

• Three ideal sources: −1.2 V, +15 V, −6 V.
• Series connection so voltages sum.
• The question asks for magnitude only (absolute value).

Concept / Approach:
Use algebraic addition: V_total = V1 + V2 + V3. After computing the signed total, take the absolute value to get the magnitude. Be careful with negative signs representing opposing polarities.

Step-by-Step Solution:

Verification / Alternative check:
Think in terms of aiding/opposing: the +15 V aids; the −1.2 V and −6 V oppose, netting 15 − (1.2 + 6) = 15 − 7.2 = 7.8 V. Same result.

Why Other Options Are Wrong:
10.2 V and 22.2 V come from incorrect addition/misplacing signs. 1.3 V is unrelated to the provided numbers. 9.6 V would be 15 − 5.4, which is not our opposing sum.

Common Pitfalls:
Dropping a sign, or forgetting that the question asks for magnitude, not signed polarity.

Final Answer:
7.8 V