Electric Charges and their Conservation

A proton carries a charge of +e. Net charge is obtained by algebraically adding all charges, so for two protons the calculation is (+e) + (+e) = +2e. Consequently, the system has two positive elementary charges, and option A is correct. The charges do not cancel because both have the same positive sign. A negative or zero result would require negative charge to be present in the combination.

Use algebraic addition of the particle charges. Two protons contribute (+e) + (+e) = +2e, while one electron contributes −e. Therefore the total is +2e − e = +e. One positive elementary charge remains, so option A is correct. It is not +3e because the electron is negative, not zero because the positive and negative amounts are unequal, and not negative because the positive charge is greater.

The net charge is the algebraic sum of all particle charges. Two electrons contribute (−e) + (−e) = −2e, and one proton contributes +e. Adding them gives −2e + e = −e. Thus one negative elementary charge remains, so option A is correct. The result is not zero because there are two negative charges but only one positive charge; it is not −3e because the proton partly cancels the negative charge.

The governing concept is quantization of electric charge. In ordinary situations, the net charge on a body is an integral multiple of the elementary charge e, so it can be written as q = ne, where n is an integer. Electrons and protons carry ±e, and transfer of whole numbers of electrons changes the body’s charge in discrete steps. Therefore option A is correct; charge is a scalar, not a vector, and it is not always zero.

Zero net charge means that the algebraic sum of positive and negative charges is zero. In a simple balanced case, the total positive charge equals the total negative charge, so they cancel in the sum and the body is electrically neutral. Therefore option A is correct. Neutrality does not mean that the body contains no particles or only neutrons. It also does not guarantee that no force can act, because neutral bodies may experience gravitational, electric polarization, or other forces.

A scalar quantity is described by magnitude alone, whereas a vector also requires a spatial direction. Electric charge has a magnitude and a sign, positive or negative, but the sign is not a geometrical direction like north, east, or upward. Charges may move, yet their motion does not make charge itself a vector. Therefore, the absence of spatial direction makes charge a scalar quantity, so option A is correct.

The conservation of charge states that the algebraic total charge of an isolated system remains constant. During friction, contact, or separation, electrons can move from one material to another; this changes the charge of each individual body, but not the combined total. Positive charge is not newly created by friction; an electron imbalance is produced. Thus option A correctly describes charge conservation.

A neutral body initially has equal amounts of positive and negative charge, so its net charge is zero. Electrons carry negative charge. If some electrons leave, the negative contribution decreases while the positive charge of the protons remains essentially fixed. The body therefore has an excess of positive charge. It is not still neutral and does not lose all charge, so option A is correct.

Electrons possess negative charge. A neutral body begins with balanced positive and negative charge. When additional electrons enter it, the negative contribution becomes greater than the positive contribution of its protons. Its net charge consequently becomes negative. The body does not become more positive or remain neutral unless an equal amount of positive charge is also added. Therefore option A is correct.

Protons carry positive elementary charge and electrons carry negative elementary charge of equal magnitude. In an ordinary neutral atom, the number of protons equals the number of electrons, so their total charges cancel: +Ze + (−Ze) = 0. Neutrons do not determine this electrical cancellation. If electrons are removed or added, the atom becomes an ion. Hence option A is correct.

The elementary charge magnitude is denoted by e and is approximately 1.6 × 10⁻¹⁹ coulomb. An electron carries charge −e, while a proton carries +e. A neutron has zero net electric charge, and a neutral atom has zero total charge rather than one elementary negative charge. Therefore the particle satisfying both the magnitude and sign conditions is the electron, so option A is correct.

The elementary charge magnitude is e. A proton carries +e, whereas an electron carries −e, so the two have equal magnitudes but opposite signs. A neutron has zero net charge, and a neutral molecule has zero total charge rather than a single positive elementary charge. Since the question requires both magnitude e and a positive sign, the proton is the only correct choice. Thus option A is correct.

Electrical neutrality means that the net electric charge is zero. A neutron has no net positive or negative charge, although it is composed of charged quarks internally; those internal charges cancel in total. It is normally located in the atomic nucleus, not outside the atom. Therefore neutrality refers to its resultant charge, not to its position or motion. Option A gives the correct reason.

Electric charge has three standard foundational properties. Additivity means the total charge is the algebraic sum of individual charges. Quantization means charge occurs in integral multiples of the elementary charge, q = ne. Conservation means the total charge of an isolated system remains constant. Direction, velocity, colour, and geometrical dimensions are not the basic properties listed here. Therefore option A is correct.

Charge quantization states that electric charge occurs in integral multiples of the elementary charge: q = ne, where n is an integer. Here q = 4e, so n = 4, which is a whole number. This directly demonstrates quantization. Friction and earthing describe methods of charge transfer, while polarization describes separation or orientation of charge, not the integral value itself. Hence option A is correct.

The governing concept is quantisation of electric charge. For an isolated body, charge is written as q = ne, where n is an integer and e is the elementary charge. Since 2.5 is not an integer, 2.5e cannot be the charge of an isolated body under ordinary school-level conditions. A body may have 2e or 3e, for example, but not 2.5e. Thus option A is correct; the other choices contradict basic properties of charge.

The governing concept is electrostatic induction or polarisation. Paper is initially neutral, but the electric field of a nearby charged rod causes positive and negative charges within its molecules to shift slightly in opposite directions. The nearer induced opposite charge experiences a stronger force than the farther similar charge, because electric force decreases with distance. The net force is therefore attractive, so option A is correct; the paper need not be permanently negative.

The governing rule is that like electric charges repel, whereas unlike charges attract. A charged object can also attract a neutral object because it induces polarisation in that object, so attraction alone cannot establish that both bodies are charged. In contrast, under the usual electrostatic conditions, observed repulsion requires repulsive charge interaction and therefore indicates that both bodies carry charge of the same sign. Hence option A is the only valid conclusion.

The governing concept is induction in a neutral body. Opposite charges certainly attract, but a charged body brought near a neutral conductor or polarizable object separates or rearranges its internal charges. The nearer induced charge has a stronger interaction than the farther charge, producing a net attraction even though the object has zero total charge. Therefore attraction by itself does not prove opposite charging. Option A is correct; the other statements deny or misstate electrostatic behaviour.

The governing concept is electrostatic equilibrium in a conductor. Conductors contain mobile charge carriers, so any excess charge moves under mutual repulsion until there is no electric field inside the conducting material. For an isolated conductor in equilibrium, the excess charge resides on its outer surface, with its density depending on surface shape. It is not confined to the centre or deep interior, and it is not destroyed. Therefore option A is correct.

The governing concept is charging by contact, also called conduction. A positively charged rod has a deficiency of electrons. When it touches the metal sphere, electrons can move from the sphere toward the rod until charge redistributes. If the sphere is then separated, it is left with a deficit of electrons and hence a net positive charge. The exact magnitude depends on the initial charges and geometry, but the possible sign is positive. Thus option A is correct.

The governing concept is charging by contact. A negatively charged rod contains excess electrons. On touching the conducting sphere, some electrons can move from the rod onto the sphere, and the charge spreads over the available conducting surface. After separation, the sphere can retain an excess of electrons and therefore becomes negatively charged. The amount is not necessarily equal to the rod's charge, but the sign is negative. Hence option A is correct; the other options ignore electron transfer.

The governing summary combines two fundamental ideas: electric charge has positive and negative forms, and the algebraic total charge of an isolated system remains constant. Charge may be transferred between bodies, so the charge on an individual object can change, but the system total does not change. Option A states both facts correctly. The other choices incorrectly deny charge types, units, conservation, or the mobility of charges in conductors.

The governing principle is conservation of electric charge. In an isolated system, the algebraic sum of all charges remains constant: total initial charge equals total final charge. Charge can be transferred between objects, and positive and negative charges may appear in pairs during processes, but the net total is not created or destroyed. It is not necessarily zero; it is simply unchanged. Therefore option A gives the correct statement, while B, C, and D are overgeneralised or false.

The governing concept is conservation of charge. Initially, each object is neutral, so the combined charge is 0 + 0 = 0. Rubbing can transfer electrons from one object to the other, making one object positive and the other negative, but it does not create net charge within the two-object system. For example, charges +q and -q still add to zero. Therefore the total charge remains zero, and option A is correct.