Directions: This section of the exam consists of questions...

Directions: This section of the exam consists of questions or incomplete statements followed by five possible answers or completions. Select the best answer or completion, and fill in the corresponding bubble on the answer sheet. The following diagram depicts a 120 -volt household circuit containing three electrical components with resistances $R_{1}=120$ ohms, $R_{2}=240$ ohms, and $R_{3}=240$ ohms. Switches $X, Y,$ and $Z$ are all originally in the open position. What current is flowing through $R_{1},$ when switches $X$ and $Y$ are closed? (A) 1.0 A (B) 1.5 A (C) 2.0 A (D) 3.0 A (E) 6.0 A

Directions: This section of the exam consists of questions or incomplete statements followed by five possible answers or completions. Select the best answer or completion, and fill in the corresponding bubble on the answer sheet.

The following diagram depicts a 120 -volt household circuit containing three electrical components with resistances $R_{1}=120$ ohms, $R_{2}=240$ ohms, and $R_{3}=240$ ohms. Switches $X, Y,$ and $Z$ are all originally in the open position.

What current is flowing through $R_{1},$ when switches $X$ and $Y$ are closed?
(A) 1.0 A
(B) 1.5 A
(C) 2.0 A
(D) 3.0 A
(E) 6.0 A

Key Concepts

Switching in Electrical Circuits

Switches in electrical circuits serve as control elements that can open or close the circuit paths, thereby altering the connectivity and effective circuit configuration. The position of a switch determines whether certain circuit branches are active or inactive, which directly influences current flow and the overall behavior of the circuit. Understanding how switches modify circuit paths is key to analyzing circuit responses in various operating conditions.

Ohm's Law

Ohm’s Law establishes the fundamental relationship between voltage, current, and resistance in an electrical circuit. It states that the voltage across a component is equal to the product of the current flowing through it and the resistance it offers. This law is essential for analyzing any circuit by allowing one to determine one of these three quantities if the other two are known.

Series and Parallel Resistor Combinations

Resistors can be arranged in series or parallel, with each configuration affecting the overall or equivalent resistance of the circuit differently. In series combinations, resistances add directly, increasing the total resistance, while in parallel arrangements, the reciprocal of the equivalent resistance is the sum of the reciprocals of each individual resistance. This concept is crucial for simplifying circuits and determining the distribution of voltages and currents.

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