Unit of Electric field: Definition, Formula, Calculation

An electric field is a field that is created around an electrically charged object in which the other electrical objects experience a specific force. An electric field is an electric property associated with a specific point in space when some charge is present. The electric field holds the nucleus and electrons together in atoms. It is also the force that is responsible for chemical bonding between atoms in molecules. The SI unit of electric field is V/m. The electric field is a vector quantity i.e. it has both magnitude and direction. It is expressed as E, known as electric field intensity or electric field strength. 

Key Terms: Electric field, Coulomb’s Law, Gauss Law, Electric Potential, Insight of electric field, unit of electric field, electric force, atoms, nucleus, electrons

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What is Electric Field?

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The electric field is the space around a charged object in which the object experiences force. It is a vector quantity which means it has both magnitude and direction. It is present everywhere in space. The electric field can be calculated by using Coulomb's law.

• The electric field is produced by electric charges.
• Electric field is measured in unit volts per metre (V/m).
• They are regions of space around the electrically charged in which other objects would feel the force.
• The variation of magnetic field or electric charges causes the electric field.
• The SI unit of the electric field is volt per meter (V/m).
• The direction of the field lines depends on the direction of the force applied to the positive charge.
• The electric field will radiate outwards, from an isolated positive charge, and the field lines will radiate inwards from an isolated negative charge.

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SI Unit of Electric Field

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The SI unit of the electric field is volts per meter (V/m). This electric field unit is equivalent to Newton per coulomb. Here, Newton is a unit of force and Coulomb is a unit of charge.

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Electric Field Formula

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The electric field is the region where a force acts on a particle placed in the field. For a charged particle with charge q, the electric field formula is given by

\(\overrightarrow E = {\overrightarrow F \over Q}\)

The unit of electric field is Newton's/coulomb or N/C. Electric force can therefore be defined as:

\(\overrightarrow F = \overrightarrow E \times Q\)

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Coulomb's Law

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As electric charges exert forces, they either attract or repel other charges. Coulomb’s law helps in calculating the force between any 2 electric point charges. The law states that the magnitude of the force between two point charges is directly proportional to the magnitudes of the charges and inversely proportional to the distance between them.

It can be represented as

\(F =k{(|q1q2|) \over r^2}\)

• where q₁ and q₂ are the charges of the point charge,
• Coulomb’s constant, k = 8.988 x 10⁹ Nm²/C², and
• r is the distance between these 2-point charges.

Technically there are no real point charges, however, electrons, protons, and other particles are so small that they can be approximated considered by a point charge.

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Electric Field – Characteristics

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A unit positive charge experiences an electric force in a region called the electric field.

• If we place a unit positive test charge at a point and bring a charge with a higher magnitude near the test charger, we will observe that either the charge experiences a push or a pull.
• This is due to the influence of the electric field.
• The force that the test charge experiences, is divided by the magnitude of the test charger and the electric field at that point.
• The direction of the electric field is the direction from which the test charge experiences force.
• Even if the test charge is removed from that point, the electric field exists.
• The SI unit of electric field is V/m. 

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Things to remember

• The electric field is the region around a charged particle, within which a force would be exerted on other charged particles or objects.
• The unit of electric field is Volts per meter (V/m).
• The direction of the electric field depends on the type of charge.
• When the charge is positive, the electric field moves outward and when the charge is negative, the electric field moves inward.
• The electric field formula is- E = F /Q
• Gauss law can be used to calculate the electric field.

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Previous Year Questions

1. When a soap bubble is charged? [KCET 2020]
2. The ratio of the charges given to the shells Q1:Q2:Q3 is….[JEE Main 2020]
3. For a uniformly charged ring of radius RR, the electric field on its axis has the largest magnitude at... [JEE Main 2019]
4. The electric field at a distance x  from the axis of rotation is…. [VITEEE 2021]
5. If  Q is the total charge of this charge distribution, the radius  R is...[VITEEE 2011]
6. An Electric Dipole Has A Fixed Dipole Moment.… [JEE 2017]
7. In the given circuit, what will be the equivalent resistance between the points…. [JIPMER 2006]
8. A hollow metal sphere of radius RR is uniformly charged. The electric field due to the sphere... [NEET 2019]
9. A solid sphere of radius R has a charge Q distributed in its volume… [BITSAT 2015]
10. The energy required to rotate the dipole by 90^∘ is….[NEET 2013]
11. When the  Gaussian spherical surface is doubled, then then the outward electric flux will be… [NEET 2011]
12. A thin disc of radius b=2a  has a concentric hole of….[JEE Main 2015]
13. Maximum torque exerted by the field on the dipole is….[KEAM]
14. Two charges of equal amount +Q are placed on a line...[WEBJEE 2016]

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