The unit of electrical resistance is:

Appeared in: RML MAINS 2025

Explanation

Ohm (symbol: Ω) is the SI derived unit of electrical resistance.
Resistance is the measure of the opposition to current flow in an electrical circuit.
According to Ohm's law, one ohm is equivalent to one volt per ampere (V/A).
This unit is named after German physicist Georg Ohm, who formulated the relationship between voltage, current, and resistance.

Option A: Ampere (A) is the unit of electric current, not resistance. It measures the flow rate of electric charge.
Option B: Volt (V) is the unit of electric potential difference (voltage), not resistance. It represents the electrical 'pressure' that drives the current.
Option D: Watt (W) is the unit of power, not resistance. It measures the rate of energy transfer or consumption.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Units of Electrical Measurement as background academic context rather than a clinical decision trigger.
Understanding basic electrical units is crucial for nurses to safely operate and troubleshoot medical equipment like ECG monitors, defibrillators, infusion pumps, and electrosurgical units.
In defibrillation and cardioversion, the concept of impedance (a form of resistance) is critical. High impedance, often due to poor electrode-skin contact, can prevent the delivery of a life-saving electrical shock.
What if? - If a patient's ECG monitor shows a 'high impedance' or 'check electrodes' alarm, it means the electrical resistance is too high for a clear signal. The nurse's immediate action should be to check the electrode pads for proper skin contact, dryness, and placement, and replace them if necessary to ensure accurate monitoring and patient safety.

How to Approach the Question

Identify the key term in the question: 'electrical resistance'.
This is a factual recall question. Access your knowledge of fundamental physics and electrical quantities.
Systematically review the options, defining each unit in your mind.
Ampere is for current. Volt is for potential difference. Watt is for power.
Identify Ohm as the specific unit for resistance.
Confirm the choice by recalling Ohm's Law (V=IR), which directly links voltage, current, and resistance.

Concept Tested & Keywords

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Practise the full RML MAINS 2025

Attempt every question from this paper in a timed mock, then review the full solution for each one.