What is the SI unit of electric field strength?

Appeared in: RRB Nsg. Superintendent 21 July 2019 (shift 1st)

Explanation

Electric field strength (E) is defined as the force (F) experienced per unit of positive electric charge (q).
The mathematical formula for electric field strength is E = F/q.
The SI unit for force (F) is the Newton (N), and the SI unit for electric charge (q) is the Coulomb (C).
Therefore, the derived SI unit for electric field strength is Newton per Coulomb (N/C).

Option A: The Henry (H) is the SI unit of inductance, a property related to magnetic fields generated by electric currents, not the force exerted by a static electric field.
Option B: Joules per Coulomb (J/C) defines electric potential, also known as voltage. It represents the potential energy per unit charge, not the force per unit charge.
Option C: This is the reciprocal (inverse) of the unit for electric field strength. It represents charge per unit force, not force per unit charge.

Visual 1: Diagram: An illustration of a positive point charge with electric field lines radiating outwards. A small positive test charge placed in the field shows a force vector pointing away from the source charge, visually representing the concept of Force per unit Charge (E = F/q).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain SI unit of electric field strength as background academic context rather than a clinical decision trigger.
While a fundamental physics concept, understanding electric fields is crucial for grasping the principles behind key medical technologies used in nursing.
Electrocardiography (ECG) and electroencephalography (EEG) work by detecting the weak electric fields generated by the heart and brain, respectively.
Defibrillators and pacemakers apply controlled electric fields to the heart muscle to restore normal rhythm or pace the heart.

How to Approach the Question

First, identify the core concept in the question, which is 'electric field strength'.
Recall the fundamental definition of this concept. Electric field strength is the force exerted on a unit of charge.
Translate this definition into a formula: E = F/q.
Identify the standard SI units for each component of the formula: Force (F) is measured in Newtons (N) and charge (q) is measured in Coulombs (C).
Substitute the units into the formula to derive the unit for the main concept: N/C.
Compare your derived unit with the given options to find the correct answer.

Concept Tested & Keywords

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Practise the full RRB Nsg. Superintendent 21 July 2019 (shift 1st)

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