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Ch 26: Direct-Current Circuits
Chapter 26, Problem 26

A triangular array of resistors is shown in Fig. E26.5. Circuit diagram showing resistors p, q, r, s with values 14.0Ω, 13.0Ω, 15.0Ω, and 8.0Ω.
What current will this array draw from a 35.0-V battery having negligible internal resistance if we connect it across (c) ac?

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1
Identify the resistors in the circuit and their respective values: 14.0 Ω, 8.0 Ω, 15.0 Ω, and 13.0 Ω.
Determine the equivalent resistance of the resistors in series and parallel combinations. For the resistors between points a and c, combine the 14.0 Ω and 8.0 Ω resistors in series, and the 15.0 Ω and 13.0 Ω resistors in series.
Calculate the total resistance of the series combinations: R1 = 14.0 Ω + 8.0 Ω and R2 = 15.0 Ω + 13.0 Ω.
Combine the equivalent resistances R1 and R2 in parallel to find the total equivalent resistance of the circuit: 1/Req = 1/R1 + 1/R2.
Use Ohm's Law (V = IR) to find the current drawn from the 35.0-V battery: I = V / Req.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ohm's Law

Ohm's Law states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. This relationship is expressed mathematically as I = V/R. Understanding this law is crucial for calculating the current in the resistor network when a voltage is applied.
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Resistance and Ohm's Law

Series and Parallel Resistor Combinations

Resistors can be combined in series or parallel configurations, affecting the total resistance in a circuit. In a series circuit, the total resistance is the sum of individual resistances, while in a parallel circuit, the total resistance can be found using the formula 1/R_total = 1/R1 + 1/R2 + ... + 1/Rn. Recognizing how the resistors in the triangular array are arranged is essential for determining the equivalent resistance and, subsequently, the current drawn from the battery.
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Combining Resistors in Series & Parallel

AC vs. DC Circuits

Alternating Current (AC) and Direct Current (DC) circuits behave differently due to the nature of the current flow. In AC circuits, the current changes direction periodically, while in DC circuits, the current flows in one direction. The question specifies connecting the resistor array to an AC source, which may involve additional considerations such as impedance and phase differences, impacting the overall current calculation.
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Related Practice
Textbook Question
A machine part has a resistor X protruding from an opening in the side. This resistor is connected to three other resistors, as shown in Fig. E26.2. An ohmmeter connected across a and b reads 2.00 Ω.

What is the resistance of X?
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Textbook Question
A triangular array of resistors is shown in Fig. E26.5.

What current will this array draw from a 35.0-V battery having negligible internal resistance if we connect it across (a) ab?
473
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Textbook Question
A triangular array of resistors is shown in Fig. E26.5.

What current will this array draw from a 35.0-V battery having negligible internal resistance if we connect it across (b) bc?
514
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1
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Textbook Question
A triangular array of resistors is shown in Fig. E26.5.

(d) If the battery has an internal resistance of 3.00Ω, what current will the array draw if the battery is connected across bc?
447
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Textbook Question
Power Rating of a Resistor. The power rating of a resistor is the maximum power the resistor can safely dissipate without too great a rise in temperature and hence damage to the resistor. (a) If the power rating of a 15-kΩ resistor is 5.0 W, what is the maximum allowable potential difference across the termi-nals of the resistor?
415
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Textbook Question
Power Rating of a Resistor. The power rating of a resistor is the maximum power the resistor can safely dissipate without too great a rise in temperature and hence damage to the resistor. (b) A 9.0-kΩ resistor is to be connected across a 120-V potential difference. What power rating is required?
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