Which of the following statements is FALSE?

RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

General Knowledge

Easy

Appeared in: RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

Explanation

The resistance of a conductor is fundamentally dependent on the nature of its material.
This intrinsic property is called resistivity (represented by the Greek letter rho, ρ), and it varies significantly between different materials (e.g., copper has low resistivity, while rubber has very high resistivity).
The statement claims resistance is 'independent' of the material, which directly contradicts the physical principles of electricity and the resistance formula R = ρ * (L/A).

Option A: This statement is true. Resistance is inversely proportional to the cross-sectional area (R ∝ 1/A). A wider path offers less opposition to the flow of current.
Option C: This statement is true. A 'thicker' wire has a larger cross-sectional area (A). As resistance is inversely proportional to area, a thicker wire will have lower resistance.
Option D: This statement is true. Resistance is directly proportional to the length of the conductor (R ∝ L). A longer path increases the opposition to current flow as electrons have a greater distance to travel.

Visual 1: Infographic - An illustration of the formula R = ρ * (L/A) with clear labels and icons representing resistivity (material type), length, and cross-sectional area.
Visual 2: Diagram - A comparison of two wires. One is long and thin, labeled 'High Resistance.' The other is short and thick, labeled 'Low Resistance.' Arrows can depict the ease of electron flow in each.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Factors affecting electrical resistance as background academic context rather than a clinical decision trigger.
Understanding electrical resistance is crucial in using medical electronics safely and effectively. For instance, ECG and EEG electrode leads are made from low-resistance materials like copper or silver to ensure accurate signal transmission from the patient to the machine with minimal signal loss.
In electrosurgery, the principle of resistance is used to generate heat. A high-frequency current passes through body tissue, and the tissue's high resistance causes it to heat up, allowing for precise cutting and coagulation.
What if? - If a defibrillator's paddles or cables were made from a material with high resistivity, much of the electrical energy would be converted to heat within the cable instead of being delivered to the patient's heart. This would render the life-saving shock ineffective and could be a safety hazard.

How to Approach the Question

First, carefully read the question and note the keyword 'FALSE'. This means you are looking for the one incorrect statement among three true statements.
Recall the fundamental formula for electrical resistance: R = ρ * (L/A).
Break down the formula into its components: R (Resistance), ρ (resistivity, which is material-dependent), L (Length), and A (Cross-sectional Area).
Systematically evaluate each option against the relationships defined in the formula.
For Option A, check the relationship between R and A. The formula shows R is proportional to 1/A (inversely proportional). The statement is TRUE.
For Option B, check the relationship between R and the material. The formula includes ρ, which is a property of the material. Therefore, R depends on the material. The statement is FALSE.

Concept Tested & Keywords

Concept Tested: Factors affecting electrical resistance
Stem keywords: resistance, conductor, cross-sectional area, material, length
Lead-in keywords: FALSE
Negative lead-in flag: The question asks to identify the FALSE statement among the options.

QIvpfACkzVgnhOCOhymXqP