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Electrostatics Foundation

electric charge properties

A complete conceptual guide for Class 12 Physics, NEET, JEE Main, JEE Advanced, IB Physics and IGCSE

  • CBSE Class 12
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  • JEE Main
  • JEE Advanced
  • IB Physics
  • IGCSE
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Royal styled electrostatics diagram with charges and electric field lines + − e

Section 1

Introduction: What Electric Charge Really Means

Electric charge is an intrinsic property of elementary particles of matter which gives rise to electric and magnetic forces. In electrostatics, it is the starting idea from which electric force, electric field, potential, capacitance, current electricity and modern electromagnetic theory are built.

Electric charge as a fundamental property

A property is called intrinsic when it belongs to the particle itself and is not acquired because of its size, shape, temperature or state of motion. An electron always carries negative charge, and a proton always carries positive charge. This charge is responsible for the electromagnetic interaction, one of the four fundamental interactions of nature.

Charge explains why a rubbed plastic comb attracts tiny paper bits, why an atom remains bound, why sparks occur, why current flows in a wire and why magnets can exert force on moving charged particles.

  • Electron charge: −e = −1.6 × 10−19 C
  • Proton charge: +e = +1.6 × 10−19 C
  • SI unit: coulomb, symbol C
  • Neutral matter: equal number of protons and electrons gives net charge zero.

Role in electrostatics, electric force and magnetic force

Electrostatics studies charges at rest. If two charged bodies are kept near each other, they exert electric forces. Like charges repel and unlike charges attract. The strength of this force later becomes Coulomb's law, but the direction of attraction or repulsion comes directly from the sign of charge.

A stationary charge produces an electric field. A moving charge produces both electric and magnetic effects. Therefore, charge is not only an electrostatic idea; it is the source of the complete electromagnetic interaction.

Exam view: Most errors in this chapter begin when students forget that charge is algebraic. The sign is not decoration; it decides force direction, net charge and electron deficiency or excess.

Section 2

Additivity of Electric Charges

The total electric charge of a system is the algebraic sum of all individual charges. Positive and negative signs must be included because charges can cancel each other.

Q_total = q1 + q2 + q3 + ... + qn = Σq

Conceptual explanation

Additivity means that the net charge of a collection of objects is obtained by simple algebraic addition. If a system has +5 C and −3 C, the total is not 8 C; it is +2 C because the negative charge cancels part of the positive charge.

This is different from mass. Mass is always positive, so total mass is an arithmetic sum. Charge may be positive, negative or zero, so the sign must always be retained. In a neutral object, the total positive charge of protons equals the total negative charge of electrons.

Example: +2 C, −5 C and +4 C gives net charge Q = +2 − 5 + 4 = +1 C.

Multiple charges inside a closed system Closed system: Q_total = (+2e) + (−3e) + (+e) + (−e) = −e +2e −3e +e −e

Five solved examples on additivity

Example 1: Charges +2 C, −5 C and +4 C are placed inside a system. Find net charge.
Q = +2 − 5 + 4 = +1 C. The system is positively charged.
Example 2: A body has charges +8 μC, −3 μC, −2 μC and +1 μC. Find net charge.
Q = 8 − 3 − 2 + 1 = +4 μC. Positive sign means deficiency of electrons.
Example 3: Three small spheres carry −6 nC, +9 nC and −4 nC. What is total charge?
Q = −6 + 9 − 4 = −1 nC. The total is negative.
Example 4: A neutral metal sphere receives −12 μC and then loses −5 μC. Find final charge.
Initial Q = 0. Receiving electrons gives −12 μC. Losing −5 μC means removing negative charge, so Q = −12 + 5 = −7 μC.
Example 5: Four particles have charges +e, +2e, −5e and +e. Find total charge in coulomb.
Q = (1 + 2 − 5 + 1)e = −e = −1.6 × 10−19 C.

Section 3

Conservation of Electric Charge

Total charge of an isolated system remains constant. Charge can neither be created nor destroyed; it can only be transferred from one body to another.

Meaning of isolated system

An isolated system does not exchange charge with its surroundings. Charges inside it may move, redistribute or appear on different objects, but the algebraic total remains unchanged. This principle is universal: it is obeyed in friction, conduction, induction, chemical reactions, nuclear reactions and particle physics.

Q_before = Q_after

If one body gains electrons, another body must lose the same number of electrons. Charging is transfer, not creation.

Charging processes

  • Friction: rubbing transfers electrons. One object becomes negative; the other becomes equally positive.
  • Conduction: charge flows through contact from a charged conductor to another conductor.
  • Induction: charge separation occurs without contact; grounding may leave a permanent charge.
  • Chemical reaction: ions form by electron transfer, but total charge of reactants and products remains equal.
  • Pair production: a gamma photon can produce electron and positron, conserving charge.
  • Annihilation: electron and positron can annihilate into photons, with net charge still zero.

Pair production and annihilation

In pair production, a neutral gamma ray photon produces an electron and a positron. The electron has charge −e and the positron has charge +e, so total charge remains zero.

γ ray photon → electron + positron
0 → −e + e = 0

In annihilation, the reverse may occur. Electron and positron combine and produce photons. Initial charge is −e + e = 0 and final photons have zero charge. Thus charge is conserved even when particles are transformed.

Exam-styleQuestion: A glass rod becomes +4 nC after rubbing with silk. What charge appears on silk?
Silk receives electrons, so charge on silk = −4 nC. Total charge remains zero.
Exam-styleQuestion: Why does conservation not mean every object keeps the same charge?
Individual objects can gain or lose charge. Conservation applies to the isolated system as a whole.
Exam-styleQuestion: An electron and positron annihilate. What is the net charge before and after?
Before: −e + e = 0. After: photons carry zero charge. Charge is conserved.

Section 4

Quantization of Charge

Electric charge exists in discrete packets. Every observable charge on a body is an integral multiple of the elementary charge.

The formula

Q = ±ne
n = 1, 2, 3, ...
e = 1.6 × 10^-19 C
n = |Q| / e

The number n must be an integer because electrons and protons are transferred as whole particles. A body cannot gain half an electron. Hence charges such as 1.5e or 2.25e are not possible for an isolated body.

Why macroscopic charge looks continuous

The elementary charge is extremely small. A charge of only 1 μC contains about 6.25 × 1012 elementary charges. Since this number is enormous, everyday charge values appear almost continuous even though they are built from discrete packets.

NEET and JEE tip: For electron-transfer numericals, calculate n = |Q|/e and then interpret the sign. Negative charge means excess electrons. Positive charge means deficiency of electrons.

Eight solved numericals on quantization

Numerical 1: How many electrons are transferred to produce −3.2 × 10−19 C?
n = |Q|/e = 3.2 × 10−19 / 1.6 × 10−19 = 2. Two electrons are added.
Numerical 2: Find charge on a body having 5 excess electrons.
Q = −ne = −5(1.6 × 10−19) = −8.0 × 10−19 C.
Numerical 3: A body has charge +4.8 × 10−19 C. How many electrons are deficient?
n = 4.8/1.6 = 3. Positive charge means 3 electrons are missing.
Numerical 4: Is 6.4 × 10−19 C possible as charge on a body?
n = 6.4/1.6 = 4. Since n is integer, this charge is possible.
Numerical 5: Is 2.4 × 10−19 C possible as charge on an isolated body?
n = 2.4/1.6 = 1.5. Since n is not integer, it is not possible.
Numerical 6: How many electrons make −1 μC charge?
n = 10−6 / 1.6 × 10−19 = 6.25 × 1012. These are excess electrons.
Numerical 7: A body loses 2.5 × 1013 electrons. Find charge acquired.
Losing electrons gives positive charge. Q = +(2.5 × 1013)(1.6 × 10−19) = +4.0 × 10−6 C.
Numerical 8: A metal sphere has charge −8 nC. Find number of excess electrons.
n = 8 × 10−9 / 1.6 × 10−19 = 5 × 1010. The sphere has 5 × 1010 excess electrons.

Section 5

Invariance of Electric Charge

The magnitude of electric charge does not depend on the speed of the charged particle. Charge at rest equals charge in motion.

Charge is relativistically invariant

In relativity, quantities such as length, time interval and relativistic momentum depend on the observer. Electric charge is different: all observers measure the same charge on a given particle. An electron moving slowly and an electron moving close to the speed of light still have charge −e.

q_rest = q_motion

This invariance is essential for the consistency of electromagnetic theory. If charge changed with speed, charge conservation would become observer-dependent, which is not observed.

Comparison with mass

In school-level language, mass is often discussed as changing with velocity in relativistic contexts, while rest mass remains invariant. Electric charge does not behave like that; it is invariant directly. A fast proton still has +e and a fast electron still has −e.

Exam phrase: Electric charge is independent of the frame of reference and hence is a relativistic invariant.

Section 6

Interaction Between Charges

Like charges repel. Unlike charges attract. The direction of electric force lies along the line joining the two charges.

Positive positive repulsion + + Positive-positive: repulsion
Negative negative repulsion − − Negative-negative: repulsion
Positive negative attraction + − Positive-negative: attraction

Force direction

For repulsion, each charge is pushed away from the other. For attraction, each charge is pulled toward the other. The forces on the two charges are equal in magnitude and opposite in direction, consistent with Newton's third law.

Section 7

Charge vs Mass

Charge and mass are both fundamental properties, but they behave very differently in addition, sign, force nature and shielding.

PropertyElectric ChargeMass
TypeElectromagnetic propertyInertial and gravitational property
SignPositive, negative or zeroAlways positive in school physics
AdditivityAlgebraic sumArithmetic sum
ConservationTotal charge is conservedMass alone is not strictly conserved in nuclear reactions; mass-energy is conserved
QuantizationQ = ±neMass is not quantized in elementary school electrostatics problems
Speed effectCharge is invariantRelativistic treatments distinguish rest mass and energy
Nature of forceAttractive or repulsiveGravitational force is attractive
ShieldingElectric effects can be shielded by conductorsGravitational shielding is not available in ordinary physics
SI unitCoulomb (C)Kilogram (kg)

Algebraic vs arithmetic

Charges cancel because signs are meaningful. Mass values do not cancel in ordinary mechanics because mass is positive.

Attraction and repulsion

Electric charge can create attraction or repulsion. Mass creates gravitational attraction only, so electric interactions can be far richer in direction.

Shielding

A conductor can shield an inner region from external electrostatic fields. This is the principle behind Faraday cages.

Section 8

Important Formula Sheet

Keep these formulas ready before attempting CBSE derivations, NEET single-correct questions and JEE numerical problems.

Additivity

Q_total = Σq

Add all charges with signs.

Quantization

Q = ±ne

n must be a whole number.

Electron count

n = |Q|/e

Use magnitude first, sign later.

Elementary charge

e = 1.6 × 10^-19 C

Charge of proton is +e; electron is −e.

Conservation

Σq_before = Σq_after

Total charge of isolated system stays constant.

Coulomb unit relation

1 C = charge transported by 1 A current in 1 s

1 C = 1 A·s.

Derivation-style exam arguments

Additivity: Suppose a system contains particles with charges q1, q2, q3, ... qn. Since electric charge can be positive or negative, the net charge is obtained by algebraic addition. Therefore, Q_total = q1 + q2 + q3 + ... + qn = Σq.

Conservation during transfer: If body A loses charge x, body B gains charge x. Initial total = qA + qB. Final total = (qA − x) + (qB + x) = qA + qB. Thus internal transfer does not change total charge.

Quantization: If each transferred electron contributes charge magnitude e and n whole electrons are transferred, total charge magnitude is ne. Including sign for deficiency or excess gives Q = ±ne, so n = |Q|/e must be an integer.

Section 9

Solved Examples

These examples are arranged by exam level. The early problems build direct formula skill; the later problems test reasoning, sign convention, conservation and multi-step interpretation.

10 CBSE-level solved examples

CBSE 1: Define electric charge and write its SI unit.
Electric charge is an intrinsic property of matter due to which bodies exert electric forces. SI unit is coulomb (C).
CBSE 2: Calculate net charge of +3 μC, −7 μC and +2 μC.
Q = +3 − 7 + 2 = −2 μC.
CBSE 3: A body has +6.4 × 10−19 C. How many electrons are missing?
n = 6.4/1.6 = 4. Positive charge means 4 electrons are deficient.
CBSE 4: Why is matter normally neutral?
Matter has equal total positive charge of protons and negative charge of electrons, so net charge is zero.
CBSE 5: State conservation of charge with an example.
Total charge of an isolated system remains constant. If a rod becomes +q by rubbing, the cloth becomes −q.
CBSE 6: Is +4.0 × 10−19 C possible on a body?
n = 4.0/1.6 = 2.5, not an integer. It is not possible as an isolated body's charge.
CBSE 7: A neutral object gains 10 electrons. Find charge.
Q = −10e = −1.6 × 10−18 C.
CBSE 8: What happens when two equal unlike charges are considered as one system?
Q_total = +q − q = 0, so the system is electrically neutral.
CBSE 9: Why is charge called algebraic?
Because positive and negative signs are included while adding charges; unlike signs can cancel.
CBSE 10: A sphere loses 5 × 108 electrons. Find charge.
Losing electrons gives positive charge. Q = 5 × 108 × 1.6 × 10−19 = 8 × 10−11 C.

10 NEET-level solved examples

NEET 1: A body has −3.2 μC charge. Find number of excess electrons.
n = 3.2 × 10−6 / 1.6 × 10−19 = 2 × 1013. Negative sign means excess electrons.
NEET 2: Which charge is possible: 8e, 2.5e, 0.75e or −12e?
Possible charges have integer n. 8e and −12e are possible; 2.5e and 0.75e are not.
NEET 3: Two bodies have +5 nC and −9 nC. They are touched and separated. What is total charge after separation?
Conservation gives Q_total = +5 − 9 = −4 nC. Distribution may change, total remains −4 nC.
NEET 4: A charged body attracts another body. Can both have same sign?
No. Same signs repel. Attraction may occur for unlike charges or between charged and neutral bodies due to induction.
NEET 5: A particle carries charge −1.6 × 10−19 C and moves fast. What is its charge in another inertial frame?
Charge is invariant, so it remains −1.6 × 10−19 C.
NEET 6: Find the charge removed when 1.25 × 1012 electrons leave a conductor.
Removed negative charge has magnitude ne = 1.25 × 1012 × 1.6 × 10−19 = 2.0 × 10−7 C. The conductor becomes +2.0 × 10−7 C.
NEET 7: A system contains charges −2e, +5e, −e and +3e. Find net charge.
Q = (−2 + 5 − 1 + 3)e = +5e = 8.0 × 10−19 C.
NEET 8: In pair production, why does an electron always appear with a positron?
A photon has zero charge. Producing only an electron would make net charge −e. Electron and positron together give −e + e = 0.
NEET 9: A body has +2 μC. Does it have excess protons moving into it?
In ordinary charging of solids, electrons move. Positive charge generally means electrons are deficient, not that protons have moved through the body.
NEET 10: If n = |Q|/e gives 3.75, what conclusion follows?
An isolated body cannot have such charge because n must be integer. The measured value would be impossible or approximate/incomplete.

10 JEE Main-level solved examples

JEE Main 1: Three charges +6 μC, −2 μC and −10 μC form an isolated system. If −3 μC is transferred from the third to the first, find final total charge.
Initial total = 6 − 2 − 10 = −6 μC. Internal transfer does not change total. Final total = −6 μC.
JEE Main 2: A neutral body loses 2 × 1015 electrons. Find charge in mC.
Q = +(2 × 1015)(1.6 × 10−19) = 3.2 × 10−4 C = 0.32 mC.
JEE Main 3: What is the least positive charge greater than 10−18 C possible on a body?
Need ne > 10−18. n > 10−18 / 1.6 × 10−19 = 6.25. Least integer n = 7. Q = 1.12 × 10−18 C.
JEE Main 4: A charge is reported as 12.8 × 10−19 C. Find n.
n = 12.8/1.6 = 8. Charge corresponds to 8 elementary charges.
JEE Main 5: A system initially has net charge +12 nC. A charge −5 nC enters from outside. What is new system charge?
Now system is not isolated during entry. New total = 12 − 5 = +7 nC.
JEE Main 6: A body A loses 1010 electrons to body B. What are charges on A and B if both were neutral?
A loses electrons: Q_A = +1.6 × 10−9 C. B gains electrons: Q_B = −1.6 × 10−9 C. Total remains zero.
JEE Main 7: If a proton is accelerated from rest, does its charge change?
No. Charge is invariant. Proton charge remains +e.
JEE Main 8: A metal sphere has charge −0.64 nC. Find excess electrons.
n = 0.64 × 10−9 / 1.6 × 10−19 = 4.0 × 109 excess electrons.
JEE Main 9: Four droplets have charges 2e, 4e, −3e and −e. They coalesce. Find final charge.
Q = (2 + 4 − 3 − 1)e = 2e. Coalescence conserves total charge.
JEE Main 10: A charged particle's measured charge is independent of velocity. Which property is verified?
Invariance of electric charge is verified.

10 JEE Advanced-level solved examples

JEE Advanced 1: Two identical neutral spheres A and B are rubbed so that 3.2 × 10−8 C is transferred from A to B in the form of electrons. Find charges.
Electrons move from A to B. A loses negative charge and becomes +3.2 × 10−8 C; B gains electrons and becomes −3.2 × 10−8 C.
JEE Advanced 2: A body has charge Q. If removing 5 × 1011 electrons makes it neutral, find Q.
Removing electrons removes negative charge. If it becomes neutral, initially it had excess electrons. Q = −(5 × 1011)(1.6 × 10−19) = −8 × 10−8 C.
JEE Advanced 3: An isolated system contains charges q, −2q and 5q. A process creates a pair +3e and −3e inside it. Find final net charge.
Initial = q − 2q + 5q = 4q. Pair has net zero. Final net charge = 4q.
JEE Advanced 4: A measured charge is 4.806 × 10−19 C. Can it represent exactly 3 elementary charges if e = 1.602 × 10−19 C?
3e = 3 × 1.602 × 10−19 = 4.806 × 10−19 C. Yes.
JEE Advanced 5: Three bodies have charges +Q, −3Q and +5Q. Electrons are transferred until charges become +2Q, x and +Q. Find x.
Conservation: initial total = Q − 3Q + 5Q = 3Q. Final total = 2Q + x + Q = 3Q + x. Hence x = 0.
JEE Advanced 6: A body A has +4e and B has −10e. What is minimum number of electrons that must move from B to A to make A neutral?
A is +4e, so it lacks 4 electrons. Move 4 electrons from B to A. A becomes neutral and B becomes −6e.
JEE Advanced 7: A charge Q = 1.0 C is built from elementary charges. Estimate n and explain why continuity approximation works.
n = 1 / 1.6 × 10−19 = 6.25 × 1018. Since n is enormous, changes by one electron are negligible on macroscopic scale.
JEE Advanced 8: A neutral conductor is polarized by induction. Does polarization violate conservation of charge?
No. Charges separate within the conductor; total positive and negative charge still cancel. Net charge remains zero unless grounding transfers charge.
JEE Advanced 9: A fast moving electron enters a detector. The detector measures −e. What principle supports this result?
Invariance of electric charge. Speed changes kinetic energy and momentum, not electric charge.
JEE Advanced 10: A system's total charge changes from +6 μC to +4 μC. What must be true about the system boundary?
The system was not isolated, or charge crossed the boundary. Conservation is not violated for a larger isolated system including surroundings.

5 IB/IGCSE-level solved examples

IB/IGCSE 1: Explain why a charged balloon sticks to a neutral wall.
The charged balloon polarizes charges in the wall. The nearer induced opposite charge attracts more strongly than the farther like charge repels, causing net attraction.
IB/IGCSE 2: A student says rubbing creates charge. Correct the statement.
Rubbing transfers electrons from one object to another. Total charge is conserved; it is not created.
IB/IGCSE 3: Find charge of 2.0 × 106 excess electrons.
Q = −ne = −(2.0 × 106)(1.6 × 10−19) = −3.2 × 10−13 C.
IB/IGCSE 4: Why can positive and negative charges neutralize each other?
Charge is algebraic. Equal magnitudes with opposite signs add to zero: +q + (−q) = 0.
IB/IGCSE 5: State one similarity and one difference between charge and mass.
Similarity: both are properties of matter. Difference: charge can be positive or negative, while mass is positive in ordinary school physics.

Section 10

Previous Year and Authentic Exam-Style Questions

The following are non-repeated, authentic-level exam-style questions aligned with CBSE, NEET, JEE Main, JEE Advanced, IB Physics and IGCSE patterns. Where an exact year is not stated, the tag is deliberately marked exam-style.

CBSE exam-styleQuestion: State the law of conservation of electric charge and illustrate it with charging by friction.
Answer: Total charge remains constant.
When glass is rubbed with silk, electrons transfer. Glass becomes positive and silk becomes negative by equal amount. Net charge of glass-silk system remains zero.
CBSE exam-styleQuestion: Why is charge on a body always an integral multiple of e?
Answer: Because charge is quantized.
Charge transfer occurs by transfer of whole electrons. Since half an electron cannot be transferred, Q = ±ne where n is an integer.
NEET exam-styleQuestion: Which of the following charges is not possible? (A) 1.6 × 10−19 C (B) 3.2 × 10−19 C (C) 4.0 × 10−19 C (D) 8.0 × 10−19 C
Answer: C
n = Q/e. For 4.0 × 10−19, n = 2.5, not an integer.
NEET exam-styleQuestion: A body has 6.25 × 1012 excess electrons. Its charge is (A) −1 μC (B) +1 μC (C) −10 μC (D) +10 μC
Answer: A
Q = −ne = −6.25 × 1012 × 1.6 × 10−19 = −10−6 C.
JEE Main exam-styleQuestion: A body is given a charge of 0.8 × 10−18 C. How many elementary charges does this represent?
Answer: 5
n = 0.8 × 10−18 / 1.6 × 10−19 = 5.
JEE Main exam-styleQuestion: The algebraic sum of charges in an isolated system is initially zero. After internal transfer of charge, it becomes:
(A) positive (B) negative (C) zero (D) depends on mass
Answer: C
Internal transfer cannot change total charge of an isolated system.
JEE Advanced exam-styleQuestion: A neutral body A transfers 109 electrons to neutral body B. Choose the correct statement. (A) A is negative, B positive (B) A positive, B negative (C) both positive (D) total charge nonzero
Answer: B
A loses electrons, so it becomes positive. B gains electrons, so it becomes negative. Total remains zero.
JEE Advanced exam-styleQuestion: A photon produces an electron-positron pair. Which property is directly demonstrated?
Answer: Conservation of electric charge.
Initial charge is zero. Final charge is −e + e = 0.
IB Physics exam-styleQuestion: Explain why electric charge is treated as invariant in relativistic motion.
Answer: It has the same value in all inertial frames.
The measured charge of a particle does not depend on its speed or the observer's inertial frame.
IGCSE exam-styleQuestion: Two objects repel each other. What can be concluded about their charges?
Answer: Both are charged with the same sign.
Repulsion is the sure test of charge. Attraction can occur between unlike charges or between charged and neutral objects.

Section 11

Common Student Mistakes

These are the errors that most often reduce marks in electrostatics numericals and theory answers.

Ignoring sign

Writing +2 C and −5 C as 7 C is wrong. Net charge is −3 C because signs must be included.

Treating charge like mass

Mass is added arithmetically, while charge is added algebraically. This difference is central.

Forgetting algebraic sum

Always write the expression first: Q_total = q1 + q2 + q3. This prevents sign slips.

Taking n as decimal

In Q = ne, n must be integer. Decimal n means the charge is not physically allowed for an isolated body.

Confusing conservation and quantization

Conservation says total charge remains constant. Quantization says charge occurs in packets of e.

Wrong unit conversion

Remember 1 μC = 10−6 C, 1 nC = 10−9 C and 1 mC = 10−3 C.

Electron deficiency/excess confusion

Positive charge means deficiency of electrons. Negative charge means excess electrons.

Section 12

Exam Strategy

Use this chapter as a scoring foundation. It is short conceptually, but it controls sign convention throughout electrostatics.

CBSE

Memorize definitions of additivity, conservation, quantization and invariance. Practice writing explanations in complete sentences with one example each.

NEET

Focus on one-line conceptual traps: possible charge values, excess/deficient electrons and repulsion as a sure test of charge.

JEE Main

Master unit conversions and fast calculations of n = |Q|/e. Expect direct MCQs with small twists in sign.

JEE Advanced

Think in systems and boundaries. Ask whether charge transfer is internal or external before applying conservation.

IB Physics

Explain concepts clearly with physical reasoning: invariance, conservation and the difference between microscopic quantization and macroscopic continuity.

IGCSE

Use simple language and diagrams. Revise attraction, repulsion, charging by friction and the electron-transfer model.

Section 13

FAQ: Properties of Electric Charge

Why is charge quantized?

Charge is quantized because it is transferred through elementary particles such as electrons and protons. Since fractional electrons are not transferred, charge appears as Q = ±ne.

Is charge always conserved?

Yes, total electric charge is conserved in an isolated system. It may move from one body to another, but the algebraic total remains constant.

Can charge exist without mass?

In school-level particle examples, charge is associated with particles such as electrons and protons. Photons have no electric charge.

Why is charge invariant?

Charge is invariant because its measured value does not depend on speed or inertial frame of reference.

What is the smallest charge?

The smallest freely observed charge in ordinary school physics is the elementary charge e = 1.6 × 10−19 C.

Why does macroscopic charge look continuous?

Because one coulomb contains 6.25 × 1018 elementary charges. The elementary step is so small that everyday charge values look continuous.

Can a body have charge 2.5e?

No. For an isolated body, charge must be an integral multiple of e. A charge of 2.5e is not allowed.

What does positive charge mean in a solid?

It usually means the solid has a deficiency of electrons. Protons remain bound inside nuclei and do not move through the solid in ordinary charging.

Why do like charges repel?

Like charges exert electric forces on each other directed away from the other charge. This is a fundamental property of electric interaction.

Is attraction a sure test of charge?

No. A charged object can attract an uncharged object due to induction. Repulsion is a better sure test that both objects are charged with the same sign.

What is the difference between conservation and quantization?

Conservation says total charge remains constant. Quantization says charge exists in discrete packets of elementary charge.

Why must signs be included in charge addition?

Because charge may be positive or negative. Algebraic addition tells whether the system has net positive charge, net negative charge or zero charge.

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