Unit of Electric Field - Difference Between Electric Field and Magnetic Field

Edited By Team Careers360 | Updated on Jul 02, 2025 04:46 PM IST

This article includes the topics like definition of the electric field, the SI unit of the electric field, Coulomb’s law, superposition principle, the concept of the uniform electric field, and the difference between electric field and magnetic field.

In the year 1855, Michael Faraday presented the term electric field. The theory of field is then developed by Faraday in terms of the electric field.

What is an electric field?

A vector quantity present in every point in the space is called an electric field. It is the electrical property of charges. Mathematically, the electric field is the ratio of electric force F to the arbitrary charge q. It is given by,

E=F/q

According to the above formula, the force F acting on an arbitrary charge q shows the electric field at that particular point. The direction of the electric field depends on the direction of the force acting on the charge. Therefore, if the charge is positive, then the electric field points in the direction of the force that is away from the charge. If the charge is negative, then the electric field direction will be opposite of the force direction that is towards the charge.

Direction of electric field and force from the positive and negative charge

Figure 1 Direction of electric field and force from the positive and negative charge

Electric field strength: The intensity of the electric field is represented quantitatively by a factor called electric field strength. It doesn’t depend on the distance from the charged body.

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This Story also Contains

What is an electric field?
What is the unit of electric field?
What is the SI unit of electric field?
Difference between electric field and magnetic field:

Coulomb’s law:

In atoms, the force of attraction between the nucleus and electrons is due to the presence of the electric field. Hence, Coulomb stated the law and gave an equation for the force of attraction or repulsion between two point charges. It states that “The magnitude of the electrostatic force of attraction or repulsion is directly proportional to the product of the magnitude of charges and inversely proportional to the square of the distance between them.” The law is represented as,

F=Kq₁q₂/r²

Where F is the force, K is the Coulomb’s constant, q₁ and q₂ are the charges, r is the distance between the charges. In vector form,

$F=\frac{1}{4\pi \epsilon_0}\frac{qq_2}{r^2}\hat{r_i}$

Here, is the permittivity in free space, ri is the unit vector representing the distance between q and qi.

We know that the electric field is the force per unit charge. If we substitute the value of force from Coulomb’s law, then the expression for electric field is,

$\vec{E}=\frac{\vec{F}}{q}=\frac{1}{4\pi \epsilon_0}\frac{q_2}{r^2}\hat{r_i}$

In general, electric field

$K\frac{Q}{r^2}\hat{r}$

What is the unit of electric field?

The unit of the electric field is calculated by the ratio of a unit of force and unit of charge.

Unit of force is Newton

Unit of charge is Coulomb

Therefore, E= F/q=Newton/Coulomb

So, the unit of the electric field is Newton per coulomb, N/C

What is the SI unit of electric field?

According to the International System of Units, the unit of the electric field is kg.m.s-³A^-1

What is the si unit of electric field strength or electric field intensity?

Electric field strength measures the intensity of the electric field. The SI unit of electric field strength or electric intensity is volt per meter, V/m or V.m^-1

Uniform electric field:

If the electric field strength or field intensity is constant at all points then it is called a uniform electric field.

State the superposition principle of the electric field.

The superposition principle of electric field states that “Every charge in space creates an electric field at point independent of the presence of other charges in that medium. The resultant electric field is a vector sum of the electric field due to individual charges”.

The total force on a charge due to any number of point charges applied on it is determined by the superposition principle. The electric field doesn’t depend on the existence of other charges. It is applicable in the calculation of the net electric field, the net electric flux, and the potential energy.

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Write the formula for the electric field around a distributed charge, an isolated point charge, and multiple charges.

The electric field around a distributed charge is given by,

$\vec{E}= \frac{1}{4\pi \epsilon_0}\int\frac{dq}{r^2}\hat{r}$

The electric field around an isolated charge is given by,

$\vec{E}= \frac{1}{4\pi \epsilon_0}\frac{dq_i}{r^2}\hat{r_i}$

The electric field around multiple charges is given by,

$\vec{E}= \frac{1}{4\pi \epsilon_0}\sum_{i}^{}\frac{q_i}{r^2}\hat{r_i}$

In the above formulas, ϵ₀ is the permittivity in free space,

$\hat{r_i}$ is the unit vector representing the distance between the charges q and q_i.

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Difference between electric field and magnetic field:

Electric field and magnetic field can be differentiated as follows:

The electric field is the force experienced by the charged particles. The magnetic field is the area around a magnetic material in which the magnetic effect is observed.
The electric field is denoted by E and the magnetic field is denoted by B.
Electric field E is the force per unit charge, E=F/q and magnetic field B is the magnetic flux per unit area, B=∅/A
The unit of the electric field is Newton per coulomb or volt per meter whereas the unit of the magnetic field is Tesla.
Positive and negative charges are present in an electric field. The magnetic field consists of the north pole and south pole.
Electric field lines move towards the positive charge and away from the negative charge. While in magnetic field lines are produced at the north pole and ended at the south pole.
An electrometer is used to determine the electric field and a magnetometer is used to determine the magnetic field.

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Frequently Asked Questions (FAQs)

1. What is the electric field symbol?

Electric field symbol is E. Electric field in vector form is denoted byE.

2. The unit of the electric field is not equivalent to_____ a) N/C b) V/m c) J/C.m d) J/C

J/C

Electric field units include N/C, V/m, and J/C.m. But J/C is the unit of potential.

3. Define electric field intensity and its si unit.

The ratio of force experienced per unit positive charge is called the electric field intensity.

SI unit of electric field intensity is Newton per coulomb or N/C.

4. Newton per meter is unit of what?

Newton per meter is the unit used in surface tension.

5. Volt per meter is the unit of what?

It is the unit of electric field strength or electric field intensity.

6. What is the unit of the magnetic field?

The unit of the magnetic field is Tesla or gauss.

7. What's the fundamental difference between electric and magnetic fields?

The fundamental difference is that electric fields are produced by electric charges, while magnetic fields are produced by moving charges (electric currents). Electric fields exert forces on stationary charges, while magnetic fields exert forces on moving charges.

8. Can electric fields exist without magnetic fields?

Yes, electric fields can exist without magnetic fields. Static electric charges produce electric fields without any associated magnetic field. However, changing electric fields can induce magnetic fields and vice versa.

9. Do magnetic fields have a similar unit to electric fields?

No, magnetic fields have different units. The unit of magnetic field is Tesla (T) or Gauss (G), which represents magnetic flux density. Unlike electric fields, magnetic field strength is measured in Amperes per meter (A/m).

10. How do electric and magnetic fields interact?

Electric and magnetic fields can interact and influence each other. Changing electric fields can induce magnetic fields, and changing magnetic fields can induce electric fields. This interplay is described by Maxwell's equations and forms the basis of electromagnetic waves.

11. What's the difference between electric field strength and electric field intensity?

There is no difference

12. How does the concept of electric field relate to Coulomb's law?

The electric field is directly derived from Coulomb's law. Coulomb's law describes the force between two charges, while the electric field represents the force per unit charge at any point in space around a charge distribution.

13. How does the strength of an electric field change with distance from a point charge?

The strength of an electric field from a point charge decreases with the square of the distance from the charge. This relationship is described by Coulomb's law and is known as the inverse square law.

14. Can the direction of an electric field be opposite to that of the force on a charge?

Yes, the direction of the electric field can be opposite to the force on a charge if the charge is negative. By convention, electric field lines point away from positive charges and towards negative charges, while the force on a negative charge is in the opposite direction of the field.

15. How do electric field lines represent the strength of an electric field?

The density of electric field lines represents the strength of the electric field. Areas with closely spaced field lines indicate a stronger electric field, while areas with more widely spaced lines indicate a weaker field.

16. Can electric fields do work?

Yes, electric fields can do work on charged particles. When a charged particle moves in an electric field, the field exerts a force on the particle, potentially changing its kinetic energy. This change in energy represents the work done by the field.

17. How does the unit of electric field relate to its definition?

The unit of electric field (N/C) directly relates to its definition: force per unit charge. It represents the force (in Newtons) experienced by a positive test charge of 1 Coulomb placed in the electric field.

18. Why is Volt per meter (V/m) also used as a unit for electric field?

Volt per meter (V/m) is used because it relates electric field to potential difference. It represents the change in electric potential (voltage) over a given distance, which is equivalent to the force per unit charge.

19. Why don't we use Coulomb per square meter (C/m²) as a unit for electric field?

Coulomb per square meter (C/m²) is the unit of electric flux density or electric displacement, not electric field. It represents the amount of electric flux passing through a unit area, which is different from the force per unit charge that defines the electric field.

20. Why don't we feel the Earth's electric field in our daily lives?

The Earth's electric field, while present, is relatively weak (about 100 N/C near the surface) and uniform. Our bodies are electrically neutral overall, so the net force on us is negligible. We only notice its effects in certain weather conditions or with sensitive instruments.

21. How does the unit of electric field (N/C) relate to energy?

The unit N/C can be related to energy through work. Moving a charge q through a distance d in a uniform electric field E requires work W = qEd. This shows how the electric field (in N/C) is linked to energy transfer.

22. What is the unit of electric field?

The unit of electric field is Newton per Coulomb (N/C) or Volt per meter (V/m). These units are equivalent and represent the force experienced by a unit positive charge in an electric field.

23. How does the concept of electric field relate to electric potential?

Electric field is the negative gradient of electric potential. In other words, the electric field points in the direction of decreasing potential, and its magnitude equals the rate of change of potential with distance.

24. How do electric fields behave in a vacuum compared to a medium?

Electric fields in a vacuum behave according to Coulomb's law without any modification. In a medium, the electric field is reduced by a factor equal to the medium's dielectric constant due to polarization of the medium.

25. How does the electric field inside a parallel plate capacitor differ from the field outside?

Inside a parallel plate capacitor, the electric field is uniform and directed from the positive to the negative plate. Outside the capacitor, the field is much weaker and non-uniform, resembling that of two oppositely charged plates.

26. How do electric fields contribute to the formation of lightning?

Lightning forms when strong electric fields build up between clouds or between clouds and the ground. These fields cause ionization of air molecules, creating a conductive path for a rapid discharge of electricity.

27. How do conductors and insulators affect electric fields?

Conductors allow charges to move freely, so in electrostatic equilibrium, the electric field inside a conductor is zero. Insulators, on the other hand, don't allow charge movement, so electric fields can exist within them.

28. What happens to the electric field at the surface of a charged conductor?

At the surface of a charged conductor, the electric field is perpendicular to the surface and proportional to the surface charge density. The field just outside the conductor is non-zero, while inside it's zero.

29. Can electric fields be visualized?

Yes, electric fields can be visualized using field lines or vector fields. Field lines show the direction of the field at each point, while vector fields represent both direction and magnitude using arrows of varying lengths.

30. What's the relationship between electric field and charge density in a continuous charge distribution?

The relationship between electric field and charge density is given by Gauss's law. It states that the electric flux through a closed surface is proportional to the enclosed charge, linking the field to the charge distribution.

31. Can electric fields be shielded?

Yes, electric fields can be shielded using conductors. This is known as electrostatic shielding or Faraday shielding. The free charges in the conductor redistribute to cancel the external field inside the conductor.

32. What's the difference between conservative and non-conservative electric fields?

Conservative electric fields, like those from static charges, have zero curl and allow for the definition of electric potential. Non-conservative fields, like those induced by changing magnetic fields, have non-zero curl and can't be associated with a scalar potential.

33. How do electric fields relate to the concept of electric flux?

Electric flux is the measure of the electric field passing through a given area. Mathematically, it's the dot product of the electric field vector and the area vector. Gauss's law relates the electric flux to the enclosed charge.

34. Can electric fields exist in perfect conductors?

In electrostatic conditions, electric fields cannot exist inside perfect conductors. Any net charge on a perfect conductor resides on its surface, and the field inside is zero due to the freedom of charge movement.

35. How do electric fields behave at sharp points on a charged conductor?

Electric fields are strongest at sharp points on a charged conductor. This is known as the "lightning rod effect." The field lines are more concentrated at these points, leading to higher field strengths and potential ionization of surrounding air.

36. What's the significance of the electric field in atomic models?

In atomic models, particularly the Bohr model, the electric field of the nucleus plays a crucial role. It provides the centripetal force that keeps electrons in orbit and determines the energy levels of electrons in atoms.

37. How do electric fields relate to the concept of electric dipoles?

Electric dipoles consist of equal and opposite charges separated by a small distance. They create non-uniform electric fields that decrease more rapidly with distance compared to point charges. The interaction of dipoles with external electric fields is important in many physical phenomena.

38. What's the difference between microscopic and macroscopic electric fields in dielectrics?

The microscopic electric field in a dielectric is the actual field at the atomic level, including contributions from individual atoms or molecules. The macroscopic field is an average over a volume containing many atoms, which is what we typically measure and use in calculations.

39. How do electric fields behave in superconductors?

In superconductors, electric fields are expelled from the interior of the material, a phenomenon known as the Meissner effect. This is related to the perfect conductivity and zero electrical resistance of superconductors.

40. Can electric fields be quantized?

In classical electromagnetism, electric fields are continuous. However, in quantum electrodynamics, the electromagnetic field is quantized, with photons being the quanta of the field. This leads to phenomena like vacuum fluctuations.

41. How do relativistic effects impact electric fields?

In special relativity, electric and magnetic fields are different aspects of a single electromagnetic field. A purely electric field in one reference frame can appear as a combination of electric and magnetic fields in another frame moving relative to the first.

42. What's the role of electric fields in capacitors?

In capacitors, electric fields store energy. The field exists between the plates of the capacitor and is responsible for separating and holding the charges on the plates. The energy stored is proportional to the square of the electric field strength.

43. How do electric fields contribute to the photoelectric effect?

In the photoelectric effect, the electric field of incident light interacts with electrons in a material. If the photons have sufficient energy (determined by their frequency), they can overcome the work function of the material and eject electrons.

44. What's the significance of critical electric field strength in dielectrics?

The critical electric field strength, or dielectric strength, is the maximum field a dielectric can withstand before breakdown occurs. Beyond this point, the insulator becomes conductive, potentially leading to spark formation or material damage.

45. How do electric fields behave in plasmas?

In plasmas, which contain free charges, electric fields can cause charge separation and complex collective behaviors. The interplay between electric fields and charged particles in plasmas is crucial in phenomena like solar flares and fusion reactions.

46. What's the connection between electric fields and electromagnetic waves?

Electromagnetic waves consist of oscillating electric and magnetic fields perpendicular to each other and to the direction of wave propagation. The electric field component of these waves interacts with charged particles, allowing for energy transfer.

47. How do electric fields relate to the concept of electromotive force (EMF)?

Electromotive force is the work done per unit charge to move charges between two points. It's related to the line integral of the electric field along a path. In a circuit, EMF is provided by sources like batteries to drive current against resistance.

48. What's the significance of electric fields in semiconductor devices?

In semiconductor devices, electric fields play crucial roles in the operation of p-n junctions, transistors, and other electronic components. They influence the movement of charge carriers (electrons and holes) and control current flow in these devices.

49. How do electric fields contribute to the functioning of particle accelerators?

Particle accelerators use strong electric fields to accelerate charged particles to high speeds. These fields provide the energy to increase the kinetic energy of the particles, often in combination with magnetic fields for steering and focusing.

50. What's the relationship between electric fields and electrical breakdown in gases?

Electrical breakdown in gases occurs when the electric field is strong enough to ionize gas molecules, creating a conductive path. This process depends on factors like gas pressure and composition, and is the basis for phenomena like corona discharge and arc formation.

51. How do electric fields behave in anisotropic materials?

In anisotropic materials, the electric field and the resulting electric displacement field may not be parallel. This is described by a dielectric tensor rather than a scalar permittivity, leading to direction-dependent electrical properties.

52. What's the role of electric fields in the operation of liquid crystal displays (LCDs)?

In LCDs, electric fields are used to control the orientation of liquid crystal molecules. By applying different field strengths, the molecules can be aligned to either block or allow light passage, forming the basis of pixel control in displays.

53. How do electric fields contribute to the phenomenon of electrophoresis?

Electrophoresis involves the movement of charged particles in a fluid under the influence of an electric field. The field exerts forces on the particles, causing them to migrate. This technique is widely used in biochemistry for separating molecules based on their charge-to-mass ratio.

54. What's the significance of electric fields in the context of atmospheric electricity?

Electric fields in the atmosphere play a role in various meteorological phenomena. They contribute to charge separation in clouds, the formation of lightning, and the global atmospheric electric circuit. Understanding these fields is crucial for weather prediction and lightning protection.

55. How do electric fields relate to the concept of polarization in dielectric materials?

Electric fields cause polarization in dielectric materials by aligning dipoles or inducing dipoles in atoms or molecules. This polarization reduces the net electric field within the dielectric and is responsible for the increased capacitance of capacitors with dielectric materials.

56. What's the connection between electric fields and the piezoelectric effect?

The piezoelectric effect involves the generation of an electric field (and thus voltage) in certain materials when mechanical stress is applied. Conversely, applying an electric field to these materials can induce mechanical strain. This relationship between electric fields and mechanical deformation is utilized in various sensors and actuators.