Electric Charge And Electrification: Definition, Types, and Properties Explained

Electric Charge And Electrification

Edited By Vishal kumar | Updated on Jul 02, 2025 06:23 PM IST

An electromagnetic field is like a giant rubber sheet where electric charges can be compared to small balls. There are positive charges (protons), negative charges (electrons) and neutral charges (neutrons) in an atom. And all objects themselves consist of positively and negatively charged particles while they tend to be neutral overall because the quantities of positive and negative charges in them are equal. However, due to these charges’ properties, some of them may attract or repel other particles or objects.

This Story also Contains

What are the Conductors and insulators?
Methods of charging
Solved Examples Based on Electric Charge And Electrification
Summary

Electric Charge And Electrification

Based on two different contexts, electrification and electric charge are the pillars upon which electricity and magnetism understanding is anchored; this forms an integral part of NEET and JEE Main exams. Electric charge is defined as one of the matter’s primary attributes; it significantly influences many other physical events and developed technologies. Electrification refers to gaining or losing electric charges while discussing materials’ response to electric fields; these include such ideas as electric potential and force due to static charge.

What are the Conductors and insulators?

When a plastic rod is rubbed with cat fur and is connected with a neutral pith ball via a copper wire, it is observed that the pith ball gets negatively charged. But when a plastic rod rubbed with cat fur is connected with a neutral pith ball via a rubber the pith ball remains neutral. That is copper allows passage of charge and rubber does not. The materials which allow passage of electricity are known as conductors and the materials which do not allow the passage of electricity are known as insulators.

Methods of charging

There are three methods

By Friction: When two bodies rub together both positive and negative charges in equal amounts appear simultaneously due to the transfer of electrons. When a glass rod is rubbed with a silk cloth, the electrons are transferred from the glass rod to the silk. The glass rod becomes positively charged and the silk rod becomes negatively charged.
By induction: When a charged body is brought near an uncharged body, one side of the neutral body becomes oppositely charged while the other side has the same charge. For example, when a positively charged glass rod is brought near a paper the paper gets attracted, this is because of the rod attracts the electrons of paper towards it so that the edge of the paper near the rod becomes negatively charged and the other end becomes positively charged due to deficiency of electrons.
By conduction: When two conductors are brought in contact, the charges will spread over both the conductors. For example, when a negatively charged plastic rod is brought in contact with a neutral pith ball some of the electrons of the rod are transferred to the pith ball and the pith ball also becomes negatively charged.

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Solved Examples Based on Electric Charge And Electrification

Example 1: Two equal spheres are identically charged with q units of electricity separately. When they are placed at a distance 3R from centre-to-centre where R is the radius of either sphere the force of repulsion between them is

1) $\frac{1}{4 π ε_{0}} \cdot \frac{q^{2}}{R^{2}}$
2) $\frac{1}{4 π ε_{0}} \cdot \frac{q^{2}}{9 R^{2}}$
3) $\frac{1}{4 π ε_{0}} \cdot \frac{q^{2}}{4 R^{2}}$
4) None of these

Solution:

By electrostatic induction

When a charged body is brought near an uncharged body, one side of the neutral body becomes oppositely charged while the other becomes the same charged.

wherein

Generally, students give the answer $\frac{1}{4 π ϵ_{0}} \frac{q^{2}}{(3 R)^{2}}$ but it is not true. Since the charges are not uniformly distributed, they cannot be treated as point charges and so we cannot apply Coulomb's law which is a law for point charges. The actual distribution is shown in the figure above.

Example 2: A table tennis ball which has been covered with conducting paint is suspended by a silk thread so that it hangs between two metal plates. One plate is earthed. When the other plate is connected to a high-voltage generator, the ball

1) Is attracted to the high-voltage plate and stays there

2) Hangs without moving

3) Swings backwards and forward hitting each plate in turn

4) None of these

Solution:

By electrostatic induction

When a charged body is brought near an uncharged body, one side of the neutral body becomes oppositely charged while the other becomes the same charged.

wherein

The table tennis ball when slightly displaced say towards the positive plate gets attracted towards the positive plate due to induced negative charge on its near surface.

The ball touches the positive plate and itself gets positively charged by the process of conduction from the plate connected to a high-voltage generator. On getting positively charged it is repelled by the positive plate and therefore the ball touches the other plate (earthed), which has a negative charge due to induction. On touching this plate, the positive charge of the ball gets neutralized and in turn the ball shares the negative charge of the earthed plate and is again repelled from this plate also, and this process is repeated again and again.

Here it should be understood that since the positive plate is connected to a high voltage generator, its potential and hence its charge will always remain the same, as soon as this plate gives some of its charge to ball, excess charge flows from the generator to the plate, and an equal negative charge is always induced on the other plate.

Example 3: Electric charges of $1 μ C, - 1 μ C$ and $2 μ C$ are placed in the air at the corners A, B and C respectively of an equilateral triangle ABC having the length of each side 10 cm. The resultant force on the charge at C is

1) 0.9 N
2) 1.8 N
3) 2.7 N
4) 3.6 N

Solution:

By conduction

When two conductors are brought into contact.

wherein

i.e. The charge will spread over both the conductors.

$\begin{aligned} F_{A} = force on C due to charge placed at A \\ = 9 \times 10^{9} \times \frac{10^{- 6} \times 2 \times 10^{- 6}}{{(10 \times 10^{- 2})}^{2}} = 1.8 N \\ F_{B} = force on C due to charge placed at B \\ = 9 \times 10^{9} \times \frac{10^{- 6} \times 2 \times 10^{- 6}}{(0.1)^{2}} = 1.8 N \end{aligned}$

The net force on C

$F_{net} = \sqrt{{(F_{A})}^{2} + {(F_{B})}^{2} + 2 F_{A} F_{B} \cos 120^{\circ}} = 1.8 N$

Hence, the answer is option (2).

Example 4: Which of the following are methods of charging?

1) Charging by friction

2) Charging by induction

3) Charging by conduction

4) All of the above

Solution:

Methods of charging

By Friction: When two bodies rub together both positive and negative charges in equal amounts appear simultaneously due to the transfer of electrons. When a glass rod is rubbed with a silk cloth, the electrons are transferred from the glass rod to the silk. The glass rod becomes positively charged and the silk rod becomes negatively charged.
By induction: When a charged body is brought near an uncharged body, one side of the neutral body becomes oppositely charged while the other side has the same charge. For example, when a positively charged glass rod is brought near a paper the paper gets attracted, this is because the rod attracts the electrons of paper towards it so that the edge of the paper near the rod becomes negatively charged and the other end becomes positively charged due to deficiency of electrons.
By conduction: When two conductors are brought in contact, the charges will spread over both the conductors. For example, when a negatively charged plastic rod is brought in contact with a neutral pith ball some of the electrons of the rod are transferred to the pith ball, and the pith ball also becomes negatively charged.

Hence, the answer is the option (4).

Example 5: Two identical balls having like charges and placed at a certain distance apart repel each other with a certain force. They are brought in contact and then moved apart to a distance equal to half their initial separation. The force of repulsion between them increases 4.5 times in comparison with the initial value. The ratio of the initial charges of the balls is

1) 2

2) 3

3) 4

4) 6

Solution:

By conduction

When two conductors are brought into contact.

wherein

i.e. The charge will spread over both the conductors.

Suppose the balls have charges Q₁ and Q₂ respectively.

$F = \frac{k {(\frac{Q_{1} + Q_{2}}{2})}^{2}}{{(\frac{r}{2})}^{2}} = \frac{k {(Q_{1} + Q_{2})}^{2}}{r^{2}}$

It is given that

$\begin{aligned} F = 4.5 F so \frac{k {(Q_{1} + Q_{2})}^{2}}{r^{2}} = 4.5 k \cdot \frac{Q_{1} Q_{2}}{r^{2}} \\ \Rightarrow {(Q_{1} + Q_{2})}^{2} = 4.5 Q_{1} Q_{2} . \end{aligned}$

On solving it gives $\frac{Q_{1}}{Q_{2}} = \frac{2}{1}$

Hence, the answer is option (1).

Summary

The electric charge is a significant element of materials that forces them to interact with magnetic fields. There are two forms of electric charge-positive and negative; materials with similar types of charges repel each other If the charges differ, partners are pulled towards each other. Electrification involves the process of rubbing some material; this may remove or increase its charge when it gets back. This can occur through various methods such as friction, conduction, and induction.

Frequently Asked Questions (FAQs)

1. How does electrification occur?

Electrification is the process of transferring electric charge between objects. It can happen through three main methods: friction (rubbing objects together), conduction (direct contact between charged and uncharged objects), and induction (charge redistribution without direct contact). These processes involve the movement of electrons between materials.

2. Why do some materials become charged when rubbed together?

When certain materials are rubbed together, electrons can transfer from one material to another due to their different abilities to attract electrons (electron affinity). The material that loses electrons becomes positively charged, while the material that gains electrons becomes negatively charged. This process is called triboelectric charging.

3. Can an object be electrically neutral but still affect nearby charges?

Yes, an electrically neutral object can still affect nearby charges through a process called polarization. When a charged object is brought near a neutral conductor or polar molecule, it can cause a redistribution of charges within the neutral object, creating local regions of positive and negative charge. This allows the neutral object to interact with other charged objects without having a net charge itself.

4. What is meant by "like charges repel, unlike charges attract"?

This phrase describes the fundamental behavior of electric charges. Objects with the same type of charge (both positive or both negative) exert a repulsive force on each other, pushing them apart. Objects with opposite charges (one positive and one negative) exert an attractive force, pulling them together. This principle is the basis for many electrostatic phenomena.

5. What is electric charge?

Electric charge is a fundamental property of matter that causes particles to attract or repel each other. It comes in two types: positive and negative. Like charges repel, while opposite charges attract. Charge is measured in coulombs (C) and is conserved in closed systems.

6. How does the concept of electric charge apply to cosmic rays?

Cosmic rays, high-energy particles from space, are mostly charged particles like protons and atomic nuclei. Their charge allows them to be deflected by magnetic fields in space, affecting their trajectories. When cosmic rays enter Earth's atmosphere, they create cascades of secondary particles through interactions governed by their charge. Detecting and analyzing these charged particles provides insights into high-energy astrophysical processes.

7. What is the difference between conductors and insulators in terms of electric charge?

Conductors are materials that allow electric charge to flow freely through them, such as metals. Insulators, on the other hand, resist the flow of electric charge. In conductors, electrons can move easily between atoms, while in insulators, electrons are tightly bound to their atoms. This difference affects how these materials behave when charged or in electric fields.

8. How does humidity affect electrostatic phenomena?

Humidity significantly affects electrostatic phenomena. In high humidity, water molecules in the air can form a thin film on surfaces, allowing charges to move more easily and dissipate. This makes it harder for objects to retain static charges. In low humidity, charges can accumulate more easily, leading to more noticeable static electricity effects.

9. What is the difference between electric charge and electric current?

Electric charge is a fundamental property of matter, measured in coulombs, that causes electrical forces. Electric current, measured in amperes, is the flow of electric charge through a conductor over time. While charge can exist without movement, current requires the motion of charged particles, typically electrons in metals.

10. How does grounding affect the charge on an object?

Grounding is the process of connecting an electrically charged object to the Earth, which acts as a vast reservoir of charge. When a charged object is grounded, electrons can flow either to or from the Earth, neutralizing the object's charge. For positively charged objects, electrons flow from the ground to the object. For negatively charged objects, excess electrons flow to the ground.

11. How does the atomic structure of an atom relate to its electric charge?

An atom's electric charge is determined by the balance between its protons and electrons. Protons in the nucleus have a positive charge, while electrons orbiting the nucleus have a negative charge. In a neutral atom, the number of protons equals the number of electrons. If an atom gains or loses electrons, it becomes an ion with a net negative or positive charge, respectively.

12. What is the principle of conservation of charge?

The principle of conservation of charge states that the total electric charge in an isolated system remains constant over time. Charge cannot be created or destroyed

13. How does the concept of quantization apply to electric charge?

Quantization of charge means that electric charge exists in discrete, indivisible units. The smallest unit of charge is the charge of a single electron or proton, denoted as e, which is approximately 1.602 × 10^-19 coulombs. All charges in nature are integer multiples of this fundamental charge, making charge a quantized property.

14. What is the relationship between electric charge and electric field?

Electric charges create electric fields around them. The electric field is a region of space around a charged object where other charged particles experience a force. The strength and direction of the electric field at any point depend on the magnitude and sign of the source charge, as well as the distance from it. This relationship is fundamental to understanding electrostatic interactions.

15. What is the relationship between electric charge and the strong and weak nuclear forces?

While electric charge is fundamental to electromagnetism, it also plays a role in the strong and weak nuclear forces. The strong force binds quarks together to form protons and neutrons, which have specific charge configurations. The weak force is responsible for certain types of radioactive decay, which can change the charge of particles. Understanding these relationships is crucial for a comprehensive view of fundamental particle interactions.

16. How does the concept of electric charge relate to plasma physics?

In plasma physics, electric charge is fundamental. Plasma is an ionized gas containing free electrons and positive ions. The behavior of these charged particles in electric and magnetic fields defines plasma characteristics. Phenomena like plasma oscillations, Debye shielding, and various waves in plasmas are all consequences of the collective behavior of these charged particles, demonstrating the importance of charge in this state of matter.

17. What is the connection between electric charge and the photoelectric effect?

The photoelectric effect, where light causes electrons to be emitted from a material, is closely related to electric charge. The energy of the incident photons must be sufficient to overcome the work function of the material, allowing electrons (negative charges) to be ejected. This phenomenon, explained by Einstein, demonstrates the particle nature of light and the quantized nature of charge transfer, linking electrostatics with quantum mechanics.

18. What is the relationship between electric charge and magnetism?

Electric charge and magnetism are intimately connected, as described by electromagnetism. Moving electric charges create magnetic fields, and changing magnetic fields induce electric currents (moving charges). This relationship is fundamental to many technologies, from electric motors to generators. The unification of electricity and magnetism by Maxwell was a pivotal moment in physics, leading to the understanding of electromagnetic waves.

19. How does quantum mechanics describe electric charge?

In quantum mechanics, electric charge is a fundamental property of particles, quantized in units of the elementary charge e. The behavior of charged particles is described by quantum electrodynamics (QED), which explains how charged particles interact through the exchange of virtual photons. This quantum description provides a deeper understanding of charge beyond classical electrostatics, explaining phenomena like the Aharonov-Bohm effect.

20. What is the significance of charge conjugation symmetry in particle physics?

Charge conjugation symmetry is a fundamental concept in particle physics that relates particles to their antiparticles by reversing all charge-like quantum numbers. This symmetry, along with parity and time reversal, forms the CPT theorem, a cornerstone of quantum field theory. Violations of charge conjugation symmetry provide insights into the matter-antimatter asymmetry of the universe, connecting electrostatics to cosmology.

21. How does the concept of electric charge relate to the Standard Model of particle physics?

In the Standard Model, electric charge is a fundamental property of elementary particles. Quarks have fractional charges, while leptons like electrons have integer charges. The electromagnetic interaction, one of the four fundamental forces, is mediated by photons exchanged between charged particles. Understanding electric charge in this context is crucial for explaining particle interactions and the structure of matter at its most fundamental level.

22. What is the relationship between electric charge and spin in quantum mechanics?

In quantum mechanics, electric charge and spin are both intrinsic properties of particles. While they are distinct concepts, they are often related. For example, in the Dirac equation, which describes relativistic quantum particles, spin naturally emerges alongside charge. The spin-statistics theorem relates a particle's spin to its behavior under exchange, which affects how charged particles can occupy quantum states, crucial for understanding atomic structure and chemistry.

23. How does the concept of electric charge apply to dark matter theories?

The concept of electric charge is significant in dark matter theories. Most dark matter candidates are proposed to be electrically neutral, as charged particles would interact with light and be more easily detectable. However, some theories propose dark matter with very small charges or exotic charge properties. Understanding how potential dark matter particles might interact electromagnetically is crucial for designing detection experiments and explaining cosmic structure formation.

24. What is the role of electric charge in quantum computing?

In quantum computing, electric charge plays various roles. Some qubit implementations, like superconducting qubits, use the charge state of Cooper pairs. Ion trap quantum computers manipulate the charge states of individual ions. Even in neutral atom qubits, precise control of electric fields is crucial for trapping and manipulating atoms. Understanding and controlling the behavior of electric charge at the quantum level is essential for advancing quantum computing technologies.

25. What is the significance of charge quantization in the development of quantum electrodynamics?

Charge quantization, the fact that electric charge comes in discrete units, was a key insight that led to the development of quantum electrodynamics (QED). This quantization suggested a deeper structure to electromagnetic interactions, leading to the concept of virtual photons mediating the force

26. What is meant by electrostatic induction?

Electrostatic induction is a process where a charged object causes a redistribution of charge in a nearby neutral object without direct contact. The charged object attracts opposite charges to the near side of the neutral object and repels like charges to the far side. This creates regions of opposite charge within the neutral object, allowing it to be attracted to the original charged object without transfer of charge.

27. What is the role of electrons in electrification processes?

Electrons play a crucial role in electrification processes as they are the charge carriers that typically move between objects. In friction, conduction, and induction, it's the transfer or redistribution of electrons that creates charge imbalances. Electrons are more mobile than protons, which are bound in atomic nuclei, making electron movement the primary mechanism for most electrification phenomena.

28. How does the triboelectric series help predict charge transfer?

The triboelectric series is a list of materials ranked by their tendency to gain or lose electrons when in contact with other materials. Materials higher in the series tend to become positively charged when rubbed against materials lower in the series, which become negatively charged. This series helps predict the direction of charge transfer in triboelectric charging, aiding in understanding and controlling static electricity.

29. What is meant by charge density, and why is it important?

Charge density refers to the amount of electric charge per unit volume, area, or length of a material. It's important because it affects the strength of electric fields and forces around charged objects. Non-uniform charge distributions can lead to complex electric field patterns. Understanding charge density is crucial for analyzing electrostatic phenomena and designing electrostatic devices.

30. How do Van de Graaff generators create large static charges?

Van de Graaff generators create large static charges through continuous charge transfer. A moving belt carries electrons from a lower electrode to an upper electrode. The upper electrode, being isolated, accumulates a large negative charge. The process continues until the electric field becomes strong enough to cause discharge. This device demonstrates charge transfer, accumulation, and the effects of large static charges.

31. How does the process of charging by induction differ from charging by conduction?

Charging by induction involves redistributing charges in an object without direct contact with the charging source. A charged object is brought near, causing charge separation, and then the object is grounded or the charges are separated. In contrast, charging by conduction involves direct contact between a charged object and an uncharged object, allowing charge to transfer directly between them.

32. What is meant by electrostatic shielding, and how does it work?

Electrostatic shielding is the process of protecting an area from external electric fields using a conducting enclosure. When an external electric field is present, charges in the conductor redistribute, creating an opposing field that cancels the external field inside the enclosure. This principle is used in Faraday cages and is crucial for protecting sensitive electronic equipment from electrostatic interference.

33. How do photocopiers and laser printers use electrostatic principles?

Photocopiers and laser printers use electrostatic principles in several steps. They use light to create a pattern of charge on a photoconductor drum, attract toner particles to this charged pattern, and then use electrostatic attraction to transfer the toner to paper. Finally, heat is used to fuse the toner to the paper. This process demonstrates practical applications of electrostatic charging, attraction, and transfer.

34. What is the difference between linear and non-linear dielectrics?

Linear dielectrics have a polarization that is directly proportional to the applied electric field. Their behavior is predictable and follows simple relationships. Non-linear dielectrics, however, have a polarization that doesn't follow this simple relationship. Their response to electric fields can be more complex, often depending on the field strength. Understanding this difference is important in advanced applications of electrostatics.

35. How does the method of images simplify electrostatic problems involving conductors?

The method of images is a problem-solving technique in electrostatics where a complex problem involving conductors is replaced with an equivalent, simpler problem. It involves replacing a conductor with an imaginary charge or set of charges that produce the same electric field outside the conductor. This method simplifies calculations and provides insights into charge distributions on conductors.

36. What is meant by electrostatic discharge (ESD), and why is it a concern in electronics?

Electrostatic discharge (ESD) is the sudden flow of electricity between two electrically charged objects caused by contact, an electrical short, or dielectric breakdown. It's a major concern in electronics because even small discharges can damage sensitive electronic components. ESD protection is crucial in manufacturing, handling, and using electronic devices to prevent costly damage and ensure reliability.

37. How do lightning rods work to protect buildings?

Lightning rods work on the principle of charge dissipation. They provide a low-resistance path for lightning to follow to the ground, diverting it away from the building structure. The sharp point of the rod also creates a high electric field, encouraging the dissipation of charge into the air, which can reduce the likelihood of a lightning strike. This demonstrates practical application of electrostatic principles in safety devices.

38. How does the concept of electric charge apply in semiconductor physics?

In semiconductor physics, the concept of electric charge is crucial for understanding the behavior of electrons and holes. Doping semiconductors introduces extra electrons (n-type) or holes (p-type), which act as charge carriers. The movement and interaction of these charges form the basis for semiconductor devices like diodes and transistors, which are fundamental to modern electronics.

39. What is the role of electric charge in chemical bonding?

Electric charge plays a vital role in chemical bonding. Ionic bonds form due to the electrostatic attraction between oppositely charged ions. Covalent bonds involve the sharing of electrons, which is influenced by the electronegativity (tendency to attract electrons) of atoms. Even in metallic bonding, the sea of delocalized electrons is held together by the positive metal ions. Understanding charge is thus essential for explaining chemical behavior.

40. How does the concept of electric charge apply to biological systems?

In biological systems, electric charge plays crucial roles. Ion channels in cell membranes control the flow of charged particles, creating electrical potentials essential for nerve signal transmission and muscle contraction. DNA, being negatively charged, interacts with positively charged proteins. Even processes like photosynthesis involve charge separation. Understanding bioelectricity is fundamental to many aspects of physiology and neuroscience.

41. What is the role of electric charge in superconductivity?

In superconductivity, electric charge plays a unique role. Superconductors allow electric current (flow of charge) with zero resistance below a critical temperature. This phenomenon is explained by the formation of Cooper pairs – pairs of electrons that can move through the material without scattering. The behavior of these charged pairs leads to effects like the Meissner effect and flux quantization, demonstrating exotic charge behavior at low temperatures.

42. How does the concept of electric charge apply to nanotechnology?

In nanotechnology, electric charge is crucial for many applications. Nanoparticles can be functionalized with specific charges to control their interactions and self-assembly. Charge transport in nanoscale devices underpins the operation of nanoscale transistors and sensors. Techniques like electrophoresis use the charge of molecules for separation and analysis. Understanding charge behavior at the nanoscale is essential for developing new materials and devices with unique properties.