Electric Charges And Fields Class 12 NCERT Solutions – Physics Chapter 1

NCERT Solutions Class 12 Physics Chapter 1 – Electric Charges And Fields

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Ans – (a) According to the supplied assertion, “Electric charge of a body is quantized,” or charged particles are incapable of moving from a single body to a different one within a portion, merely the integral quantity (1,2,3,…,n) of electrons may be exchanged.
Since the electrical charge of a single electron is fundamentally charged in nature, the energy on any substance is equal to the inherent multiple of the energy upon the electron itself. It can be represented by a mathematical equation known as, q= ±ne.
Here, n is the total amount of electrons exchanged and e is the amount of charge present in a single electron, which can potentially be used to represent the energy of any substance.

(b) The overall amount of electrical charges is equal to the amount of electrical energy that is visibly present on a macroscopic or huge level. Accordingly, electrical charges are seen to be continuous hence quantification is negligible at the macroscopic level.

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Ans – When two separate objects are rubbed together, electrical charges of opposing type and similar magnitude are created on both surfaces. This occurs as a result of electrical charges being generated in tandem. We refer to this phenomenon as charging via friction.
However, because opposing forces of identical size destroy one another, the system’s net value stays unchanged. The rule of conservation of energy is therefore shown to be compatible with the fact that scratching a metal rod with a silky fabric produces opposing forces with identical intensity on each of these objects.

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Ans – (a) When an electrical charge gets embedded in an electrically charged environment, it feels an ongoing pull, which results in a continuous curve referred to as an electrostatic field vector.
The amount of charge that travels across the sectional area of a wire of electricity carrying one ampere of electrical energy in one second is known as the unit charge. The field boundaries won’t abruptly break since the electrical charge doesn’t bounce from one place to another.

(b) When 2 field paths are observed to pass through across one another at a place, it could indicate that the intensity of the electric field possesses two distinct routes at that particular location, since two separate deviations (indicating the trajectory of electric field intensity around particular spot) may be formed at the area of junction. Meanwhile, 2 separate field lines would never intersect one another because this would not be feasible.

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Ans – (a) A specific amount of charged particles undergo conversion from genuine wool to polythene whenever the two different materials are massaged together. This causes polythene to transform into a negatively charged element when it gains electrons & woollen element to gain a positive charge when it loses them.

As we all know,

The electrical charge present across the polyethylene piece would be, q = −3×10⁻⁷ C 

Meanwhile, the charge of an electron is represented as, e = −1.6×10⁻¹⁹ C  Assuming n is the number of electron particles that are moved from wool to polythene, we may infer through the quantization characteristic that,

Consequently, the total amount of electrons being carried through wool to polythene might constitute 1.87×10¹².

(b) Yes. During the transfer of electrons from wool to polythene, mass is also exchanged along with charge. Let m be the mass transferred and m_e be mass of the electron,

Hence, we determined that a negligible quantity of mass is transferred from wool to polythene.

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Ans – We may infer from the established features of electrical charges that similar ones oppose one another and contrasting charges draw one another. Accordingly, components 1 and 2 could become negatively charged if they moved in the direction of the plate that was positively charged despite repelling back from the negatively charged surface, and component 3 would ultimately become positively charged if they moved in the opposite direction of the negatively charged surface and repelled aside over the positively charged surface.

As we are well aware of the fact that, for any specific velocity, the change in displacement or quantity of deflection has become directly proportional to the charge-to-mass proportion, or electromagnetic field (emf). Element 3 is likely to have the largest charge-to-mass proportion as its deviation is the greatest between the 3 existing components.

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Ans – Each of the cube’s edges has been demonstrated to be parallel with their respective coordinate axes. There are exactly as many field lines entering the cube as there are field lines exiting the cube. Consequently, there would be no net flow within the cube.

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(b) No. According to Gauss’s law, it clearly states that the net flow leaving an object is determined by the amount of charge inside it. Therefore, it may be concluded that the amount of remaining charge within the material is zero when the net flow is considered to have the value zero.

Nevertheless, we are unable to infer that there were indeed no charges present within the enclosed space since the body’s overall charge of zero just indicates that there are a comparable amount of both positive & negative charges available inside the element itself.

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Ans – (a) As we all know from the above statement:

The total amount of electrical flux because of the mentioned point charge would be,
ϕ = −1.0×10³ Nm²/C 

Meanwhile, the radius of the Gaussian element containing the point charge is considered to be,
r=10.0 cm

Due to Gauss’s law, the amount of electrical flux that pierces an object is determined based on the total charge that the material encloses. Subsequently, this effect is not influenced depending on the size of the arbitrary area that is thought to encapsulate this electrical charge. Therefore, the amount of energy flowing through the Gaussian field stays identical if its outer diameter is increased by twofold. i.e., −10³ Nm²/C.

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