Question

The circuit diagram below shows a 9 V battery in a circuit with three resistors labelled 1, 2, and 3. What is the voltage drop across the resistor?

(A) 3 V
(B) 9 V
(C) 27 V
(D) 81 V
(E) It is impossible to determine the voltage drop without knowing the resistance value.

Answer 1

Hint:
The potential difference across a component depends on its resistance and the current flowing through it. For series and parallel combinations of resistances, the voltage across the components is different depending on the arrangement.

Complete step by step answer:
In electric circuits, various combinations of resistors are used to obtain different results. The most common arrangements include the series and the parallel combination of resistances. In a series combination, the resistances are connected side by side with each other. Consequently, the same current flows through all of them, but depending on the resistor value the voltage varies.
In a parallel combination of resistances, all of the resistors are connected to the same node through independent connecting wires. As a result, the current flowing through each of these depends on the resistance, while the voltage drop across the nodes remains the same.
In this question, as we are provided with a parallel combination of resistances and there are no other external resistors connected in the circuit, the voltage drop will be the same as that of the battery i.e. 9 V.
Hence, the correct answer is option (B).

Note:
Ohm’s Law gives the relationship between the voltage drop and the electric current in an electrical circuit. It states that the potential difference is directly proportional to the current flowing through a component, and the constant of proportionality is substituted using resistance of the component.