Cathodic Protection Tester Practice Exam

What does the Voltage Law state regarding voltages around a closed loop in a series circuit?

1. The sum of the source voltages equals the sum of the voltage across resistances.

2. The total voltage must equal the resistance in the circuit.

3. The voltage drop across any resistance is always zero.

4. The total current in the circuit must equal the impedance.

The correct answer is: The sum of the source voltages equals the sum of the voltage across resistances.

The correct response refers to the Voltage Law, often associated with Kirchhoff's Voltage Law (KVL), which states that the sum of the voltages around a closed loop in a series circuit must equal zero. In other words, it asserts that the algebraic sum of all voltages in a closed loop must satisfy the equation where the total voltage supplied by sources is equal to the total voltage drop across resistive elements. This concept is fundamentally rooted in the principle of energy conservation, where the energy supplied by the voltage sources is used to overcome the energy lost across resistive elements in the circuit. If you were to sum all the voltage contributions from sources and subtract the voltage drops across each resistance, the resulting value will equal zero, which aligns with the idea that energy is neither created nor destroyed in the circuit. In contrast, interpretations of other choices diverge from this vital concept. The notion that the total voltage must equal the resistance does not reflect the relationship among voltages and resistances but rather suggests a misunderstanding of Ohm's Law, which relates voltage and resistance based on current. Claiming that the voltage drop across any resistance is always zero contradicts fundamental circuit behavior, as resistances inherently have voltage drops proportional to the current flowing through them