Electric Charges and their Conservation

Correct answer: B. Coulomb

Explanation: The SI unit of electric charge is the coulomb, represented by C. Charge may also be related to current through Q = It, so one coulomb is the charge transported by a current of one ampere in one second. Newton measures force, metre measures length, and watt measures power. These alternatives belong to different physical quantities and cannot represent charge. Therefore option B is correct.

Correct answer: B. Coulomb

Explanation: The SI unit of electric charge is the coulomb, represented by C, so option B is correct. A coulomb is the amount of charge transported by a current of one ampere in one second. Newton measures force, joule measures energy, and metre measures length. Confusing coulomb with newton is especially common because charge and force occur together in Coulomb’s law.

Correct answer: A. A pair of equal and opposite charges separated by a small distance

Explanation: An electric dipole consists of two point charges having equal magnitudes and opposite signs, separated by a small but finite distance. Its dipole moment is directed from the negative charge to the positive charge and has magnitude p = qd. Two like charges do not form a dipole, while a single charge is a monopole. Thus option A gives the complete definition.

Correct answer: A. Coulomb

Explanation: The governing concept is the SI measurement of electric charge. Charge is represented by Q and its SI unit is the coulomb, written C. One coulomb is the amount of charge transferred by a current of one ampere in one second, so 1 C = 1 A s. Newton is a unit of force, volt measures potential difference, and ampere measures electric current; therefore option A is correct.

Correct answer: B. Two

Explanation: The governing concept is the classification of electric charge. In elementary electrostatics, charge occurs in two kinds: positive and negative. Charges of the same kind repel, while charges of opposite kinds attract, which explains many basic electrostatic observations. The question asks for kinds, not the number of particles or the magnitude of charge. Therefore option B is correct; options A, C, and D give incorrect counts.

Correct answer: B. Repulsion

Explanation: The governing rule of electrostatics is that like charges repel and unlike charges attract. Charges of the same nature have the same sign: both may be positive or both may be negative. The electrostatic force between them therefore acts outward, tending to increase their separation. Hence option B, repulsion, is correct. Attraction applies to opposite charges, while charge does not disappear merely because two charges interact.

Correct answer: B. Attraction

Explanation: The governing electrostatic rule states that unlike charges attract each other. Opposite-nature charges have opposite signs, such as one positive charge and one negative charge. The electric force on each charge is directed toward the other, so the separation tends to decrease. Therefore option B, attraction, is correct. Repulsion is associated with like charges, and interaction does not make both charges zero.

Correct answer: B. Electron

Explanation: The governing atomic-charge concept identifies the electron as the elementary particle with negative charge, written as −e. A proton carries an equal-magnitude positive charge, while a neutron has zero net charge. An atomic nucleus contains protons and neutrons and is therefore normally positive when it has protons. Hence option B, electron, is the only unambiguous correct answer. In ordinary charging, electrons are the particles transferred between bodies.

Correct answer: C. Proton

Explanation: The governing concept of atomic charge is that a proton carries one positive elementary charge, +e. An electron carries −e, whereas a neutron has no net electric charge. A photon is electrically neutral, even though it carries energy and momentum. Thus option C, proton, is correct. A body becomes positively charged when it has fewer electrons than protons; this does not mean that protons normally leave the nuclei during ordinary charging.

Correct answer: C. Zero

Explanation: The governing atomic-structure concept is that a neutron is electrically neutral. Its net electric charge is zero, even though it is made of charged quarks internally; at school level, its observable total charge is written as 0. A proton is positive and an electron is negative, so neither sign applies to a neutron. Therefore option C, zero, is correct. “Double positive” is not a property of a neutron.

Correct answer: C. Total charge remains constant in an isolated system

Explanation: The governing conservation law states that the algebraic sum of electric charge in an isolated system remains constant. Charge may be transferred from one body to another, so individual objects can become positive or negative, but the total charge of the complete isolated system does not change. It is not created or destroyed in ordinary processes. Therefore option C is correct; option D is wrong because a neutral total does not require every object to be neutral.

Correct answer: B. Positive

Explanation: The governing charge-balance idea is that electrons carry negative charge, while the positive charge of nuclei usually remains fixed in a solid body. If electrons are removed, the body loses negative charge but retains the same positive nuclear charge. Its net charge therefore becomes positive. Hence option B is correct. Gaining electrons would produce a negative body, whereas neutrality requires equal total positive and negative charge; simply removing electrons cannot leave the charge unchanged.

Correct answer: B. Negative

Explanation: The governing principle is charge balance: every electron contributes negative elementary charge. When a body gains additional electrons, its negative charge increases while the positive charge of its nuclei does not increase correspondingly. The net charge therefore becomes negative, making option B correct. A positive body has an electron deficit, and a neutral or uncharged body has balanced positive and negative charge rather than an excess of electrons.

Correct answer: C. Electrons

Explanation: The governing concept in charging by friction is transfer of electrons between the outer surfaces of materials. In ordinary solids, protons and neutrons are tightly bound inside atomic nuclei, and entire nuclei do not move from one object to another. Electrons are much more mobile and can be transferred because of differences in material affinity. Therefore option C is correct. The body gaining electrons becomes negative, while the body losing them becomes positive.

Correct answer: C. Its total positive and negative charges are equal

Explanation: The governing concept is net charge. An electrically neutral body can contain protons, electrons, and other particles, but its total positive charge equals its total negative charge, so the algebraic sum is zero. Therefore option C is correct. Neutral does not mean that the body has no particles or no internal charges. Options A and B describe a net positive or net negative condition, not electrical neutrality.

Correct answer: B. Charge exists in integral multiples of elementary charge

Explanation: Quantization is the property that electric charge occurs in discrete units rather than in every possible continuous value. For an ordinary isolated body, charge is written as q = ne, where n is an integer, positive, negative, or zero, and e is the elementary charge. Thus option B is correct; arbitrary fractional charge is not allowed in this school-level model, while zero charge is only one special case.

Correct answer: A. q = ne

Explanation: The quantization principle gives the charge on a body as q = ne. Here q is the net charge, e is the magnitude of elementary charge, and n is an integer such as 0, ±1, ±2, and so on. Therefore option A is correct. The expressions e/n and n/e do not represent integral multiples of e, and charge is not always zero.

Correct answer: A. 1.6 × 10⁻¹⁹ C

Explanation: The elementary charge e is the magnitude of the charge carried by one proton or one electron. Its accepted approximate value is e = 1.6 × 10⁻¹⁹ coulomb. A proton has +e and an electron has −e, but their magnitudes are equal. Option A is therefore correct; 9 × 10⁹ is Coulomb’s-law’s constant, 6.6 × 10⁻³⁴ is associated with Planck’s constant, and 3 × 10⁸ is approximately the speed of light.

Correct answer: A. They are equal

Explanation: An electron carries charge −e, whereas a proton carries charge +e. The signs are opposite, indicating different charge types, but the magnitudes are both e = 1.6 × 10⁻¹⁹ C. Hence option A is correct. Option B and C confuse sign or particle identity with magnitude, and option D is false because neither particle is electrically neutral. A proton-electron pair can have zero net charge only after algebraic addition.

Correct answer: C. e/2

Explanation: For an isolated ordinary body, charge is quantized according to q = ne, where n must be an integer. Values 2e, 3e, and 10e correspond to n = 2, 3, and 10, so they are possible in this model. The value e/2 would require n = 1/2, which is not an integer. Therefore option C is the impossible charge among the given choices.

Correct answer: A. Total charge equals the algebraic sum of individual charges

Explanation: The additive property states that the net charge of a system is obtained by adding every individual charge algebraically, including its sign: Q = q₁ + q₂ + q₃ + ... . For example, +5 C and −2 C give Q = +3 C, not necessarily zero. Thus option A is correct. Zero total charge is only a special cancellation case; charges can be added, and their signs do not imply that one magnitude is always smaller.

Correct answer: C. 0 C

Explanation: Net charge is found by adding charges algebraically, so Q = (+2 C) + (−2 C). The positive and negative contributions have equal magnitudes and opposite signs; therefore Q = 0 C. Option C is correct. The value 4 C would result from adding magnitudes without signs, 2 C ignores one contribution, and 1 C has no basis in the stated data. Charge cancellation does not mean that the individual charges were absent.

Correct answer: C. Zero

Explanation: Initially, the two neutral bodies together have total charge zero. When electrons transfer, the donor body loses negative charge and becomes positive, while the receiving body gains the same negative charge and becomes negative. The charge has been redistributed, not created or destroyed. Thus the algebraic total remains zero, so option C is correct. The signs in A and B can describe individual bodies, but not the complete isolated system.

Correct answer: A. Positive

Explanation: Rubbing does not create charge; it transfers electrons between materials. In the conventional glass-and-silk example, electrons move from the glass rod to the silk. The glass therefore loses negative charge and is left with a net positive charge. Option A is correct. The silk becomes negative, but that does not make the rod neutral or simultaneously positive and negative in the intended net-charge sense; the total charge of the pair remains conserved.

Correct answer: B. Negative

Explanation: In the conventional triboelectric example, rubbing causes electrons to move from the glass rod onto the silk. Silk therefore gains excess electrons and acquires a net negative charge. Hence option B is correct. The glass becomes positive because it loses those electrons, while the pair as a whole remains electrically conserved. Options C and D incorrectly ignore the electron transfer, and A reverses the usual charge assignment for silk.