Electric Charges and their Conservation

The governing concept is conservation of charge. Rubbing two different materials may cause electrons to transfer from one surface to the other, so one object becomes negative and the other positive. The charges appear separately, but the algebraic total charge of the isolated pair does not increase. Therefore, saying that friction creates new net charge is incorrect; it merely separates existing charge.

For equal newly appearing charges, the algebraic sum is (+q) + (−q) = 0. In an isolated system, charge conservation means the total charge before and after the process must be the same. The positive and negative charges may be produced as a pair or separated between objects, but they do not change the system’s net charge. Thus the total charge has zero change.

The sign of net charge compares the amounts of positive and negative charge. A net value of −2 C means the object has 2 C more negative charge than positive charge, normally because it has gained excess electrons. It does not mean the object has no particles or only neutrons. A positive net value, in contrast, would indicate a deficit of electrons or excess positive charge.

A positive net charge means that the positive charge exceeds the negative charge by the stated amount. For an ordinary object, this usually results from the loss of electrons, because protons remain bound in nuclei. Thus +2 C indicates an excess of positive charge, or equivalently a deficit of electrons. It cannot represent a neutral object, zero charge, or an excess of electrons.

The SI unit of electric charge is the coulomb, represented by C. Charge can also be related to current through Q = It, so one coulomb is the charge transferred by a current of one ampere in one second. Newton measures force, metre measures length, and joule measures energy; therefore none of those units can be used as the SI unit of charge.

Ordinary charging involves the transfer of relatively mobile electrons, not the removal of nuclear particles. A proton is located in an atom’s nucleus and is held there by the strong nuclear interaction, so ordinary rubbing or contact cannot free it from the atom. Option A is correct. Protons are positively charged and have mass, so B and C are false; D is false because protons are inside atoms.

The governing idea is conservation of electric charge during frictional charging. Different materials hold their outer electrons with different strengths, so rubbing can transfer electrons from one surface to the other. The electron-losing object has a positive net charge, while the electron-gaining object has a negative net charge. Thus A is correct; protons and neutrons do not cause this transfer, and charge is not newly created.

Connecting a conductor to the Earth is called earthing or grounding. The Earth acts as a very large charge reservoir, allowing electrons to enter or leave the conductor until the relevant electrical condition is reached. Therefore option A is correct. Magnetisation concerns magnetic properties, diffusion concerns particle spreading, and boiling is a change of state; none describes an electrical connection to Earth.

Earthing provides a conducting path between an object and the Earth, which can accept excess electrons or supply electrons when the object has an electron deficiency. Charge therefore moves until the object reaches electrical balance, without destroying matter or protons. Option A states this effect correctly. Mass does not disappear, melting is unrelated to ordinary earthing, and protons remain bound in nuclei.

A positively charged object has fewer electrons than it would have in its neutral state. When it is connected to Earth, the potential difference drives electrons from the Earth, which can supply or replace the deficit. Thus option A is correct. Protons cannot normally leave atomic nuclei, neutrons carry no net charge, and photons are not the charge carriers that neutralise the object in this process.

A negatively charged object contains an excess of electrons relative to its neutral condition. On earthing, these mobile excess electrons can flow through the conducting connection from the object into the Earth, a much larger charge reservoir. Therefore option A is correct. Electrons would not normally flow from Earth into an already electron-rich object, and the remaining choices do not describe the earthing path.

Neutrality refers to the algebraic sum of charge, not to the absence of matter or charged particles. In an ordinary neutral object, positive and negative charges are both present in balanced amounts, so the net charge is zero: positive charge plus negative charge equals zero. Option A is correct. The object still contains atoms and particles; options B, C, and D therefore misstate neutrality.

Conservation of charge means that the total algebraic charge of an isolated system remains constant; charge is transferred rather than created or destroyed. During rubbing, electrons move from one object to the other. If one object loses charge +q and the other gains −q, their combined change is +q − q = 0. Hence A is correct, while B, C, and D illustrate other physical processes.

The governing concept is conservation of electric charge. When the charged conductor touches the identical neutral conductor, charge may flow and redistribute between them, but no charge is created or destroyed in the isolated pair. Thus, although the charge on each individual conductor may change, their combined algebraic charge remains equal to its initial value. Therefore option A is correct; zero, doubled, or vanished total charge would violate conservation.

Equal sharing uses conservation of charge and division by the number of identical spheres. The total charge is +6 C and there are two spheres, so the charge on each is Q/2 = (+6 C)/2 = +3 C. The positive sign is retained because both spheres together receive the original positive charge. Hence option A is correct; +6 C ignores sharing, +12 C doubles the charge, and zero violates conservation.

The governing idea is that electric charge is a signed scalar quantity. In an algebraic sum, positive and negative charges are included with their respective signs; for example, (+5 C) + (−2 C) = +3 C. Adding magnitudes alone would give the wrong result whenever opposite charges occur. Therefore option A correctly describes the method, while options B, C, and D omit necessary sign information or ignore one type of charge.

The governing rule is algebraic addition of electric charges. Both given charges are positive, so their signs agree and their magnitudes are added: (+2 C) + (+3 C) = +5 C. The result keeps the positive sign. Thus option A is correct. One coulomb results from subtraction, negative five changes the sign without justification, and zero would incorrectly suggest complete cancellation despite both charges being positive.

Electric charge must be added algebraically, including its sign. Here the calculation is (−2 C) + (−3 C) = −(2 + 3) C = −5 C. Since both charges have the same negative sign, their magnitudes add and the negative sign remains. Option A is therefore correct. Positive five reverses the sign, negative one uses an incorrect subtraction, and zero would require equal opposite charges, which are not present.

The governing concept is signed, or algebraic, addition of charge. Write the quantities as +7 C and −4 C, then calculate (+7 C) + (−4 C) = +3 C. Because the positive magnitude is larger, the result is positive and its magnitude is the difference, 7 − 4 = 3 C. Therefore option A is correct; +11 ignores the opposite sign, −3 reverses the dominant sign, and zero is not the calculated result.

Use algebraic addition because the charges have opposite signs. The calculation is (−7 C) + (+4 C) = −3 C. The negative charge has the greater magnitude, so the final sign is negative, while the magnitude is the difference 7 − 4 = 3 C. Hence option A is correct. Positive three assigns the wrong dominant sign, negative eleven adds magnitudes incorrectly, and zero would require equal magnitudes.

The governing principle is conservation of the algebraic total charge, so the sign and value of every initial and final charge must be known. The first step is therefore to list all charges with their positive or negative signs and units. Only then can initial and final totals be compared correctly. Option A is correct; selecting one charge, ignoring units, or treating opposite signs as identical can produce an invalid conservation equation.

The quantization of charge is expressed as q = ne, where n is an integer and e is the elementary charge. A positive value q = +5e means the body has lost five electrons compared with its neutral state. Protons normally remain bound in the nucleus, so they do not move during ordinary charging. Therefore option A is correct; excess electrons would produce a negative charge, while neutrons and proton loss do not explain this result.

Net charge is the algebraic sum of all charges, so their signs must be included. Taking the elementary charge as e, q_net = 3e + 5(-e) = 3e - 5e = -2e. Thus the system has a net charge of two elementary charges of negative sign. Option B reverses the sign, option C ignores cancellation, and option D incorrectly assumes complete balance.

Charge quantization means that the net charge of an isolated ordinary body is written as q = ne, where n is an integer and e is the elementary charge. Consequently, charge occurs in integral multiples such as 0, ±e, ±2e, and so on, rather than arbitrary fractions of e. Option A states this principle correctly. Options B, C, and D either deny discreteness or confuse charge with mass.

Electrostatic repulsion is a distinctive result of two like charges: positive with positive or negative with negative. A neutral object can be attracted to a charged object because of polarization, but two neutral objects do not normally repel solely through electrostatic charge effects. Opposite charges attract rather than repel. Hence option A is the most appropriate conclusion, although the magnitudes of the two charges need not be equal.