Series–parallel resistance between two nodes A and B A network consists of two ideal resistors connected in simple series between nodes A and B: a 10 Ω resistor followed by a 1 kΩ (1000 Ω) resistor. For this explicit series connection, what is the total equivalent resistance RT seen between A and B?
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A1,010 Ω
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B100 Ω
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C900 Ω
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D10 Ω
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E10,100 Ω
Answer
Correct Answer: 1,010 Ω
Explanation
Introduction / Context:This question checks your ability to compute the equivalent resistance of a strictly series connection. Series networks are everywhere in bias chains, current-limiting paths, and sensor dividers. Getting comfortable with series addition is essential before moving to mixed series–parallel reductions and Thevenin/Norton modeling.
Given Data / Assumptions:
- Two ideal resistors are connected in series between nodes A and B.
- R1 = 10 Ω and R2 = 1 kΩ (1000 Ω).
- Conductors are ideal; there are no hidden branches or parallel paths.
- We seek RT as seen between A and B.
Concept / Approach:For resistors in series, the equivalent resistance is the arithmetic sum of the individual resistances. The rule is topology-based and independent of excitation (DC or AC) as long as elements are linear resistors. The governing relation is: R_total = R1 + R2 + … + Rn. Once RT is known, any loop current under a given source follows directly from I = V / RT.
Step-by-Step Solution:
Identify the connection as pure series (one single current path).Write the sum: RT = R1 + R2.Insert values in ohms: RT = 10 + 1000 = 1010 Ω.Report RT to match option formatting: 1,010 Ω.Verification / Alternative check:Use a quick current check. With a 10 V ideal source across A–B, I = 10 / 1010 ≈ 9.90 mA. The drops would be V_R1 ≈ 0.099 V and V_R2 ≈ 9.90 V, which sum back to 10 V, confirming series behavior and the calculated RT.
Why Other Options Are Wrong:
100 Ω: would imply a different network (e.g., partial parallel) that is not given.900 Ω: does not equal the sum 10 + 1000.10 Ω: ignores the 1 kΩ element entirely.10,100 Ω: a misplaced digit error; it is a common slip when adding mixed units.Common Pitfalls:Confusing series with parallel (parallel uses reciprocals); mixing kΩ and Ω without converting; accidentally omitting a component or misreading comma formatting in values.
Final Answer:1,010 Ω