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Electric Charge, Quantization and Conservation

This category covers the basic concepts of electric charge, how charge is quantized, and the principle of charge conservation. It includes questions that test understanding of charge interactions, measurement units, and the laws governing charge in physical systems.

30 questions

A conducting sphere of radius 27 cm has an electric field of \( 6 \times 10^3 \, \text{N/C} \) at 54 cm from its center.

**Fundamental property of charge** includes additivity and quantization, meaning net charge equals algebraic sum of constituents and each is multiple of e. When rod loses charge, electron removal is inferred, and n = q/e gives transferred count. E = (k q/r²) . 6 × 10³ = 9 × 10⁹ × (q/(0.54)²) . q = (6 × 10³ × 0.2916/9 × 10⁹) = 1.944 × 10⁻⁷ C . Substituting values gives 1.944 × 10⁻⁷ C, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

Ref: NCERT > Physics Book > Electric Charges and Fields > Electric Charge, Quantization and Conservation

A point charge \( -9 \, \mu\text{C} \) is at the origin. What is the electric field magnitude at a point 6 m along the x

**Charge conservation and quantization** govern rubbing processes where electrons transfer without creation. Total charge before and after remains equal, and any measured charge corresponds to n = q/e electrons, allowing counting of carriers from coulomb value. E = (k |q|/r²) . k = 9 × 10⁹ N·m²/C² , q = 9 × 10⁻⁶ C , r = 6 m . E = 9 × 10⁹ × (9 × 10⁻⁶/(6)²) = 9 × 10⁹ × (9 × 10⁻⁶/36) = 2.25 × 10³ N/C . Substituting values gives 2.25 × 10³ N/C, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

Ref: NCERT > Physics Book > Electric Charges and Fields > Electric Charge, Quantization and Conservation

Two charges \( +10 \, \mu\text{C} \) and \( -2 \, \mu\text{C} \) are 80 cm apart. What is the distance from \( +10 \, \m

**Quantization of charge** states observable charge is integer multiple of elementary charge e = 1.6×10⁻¹⁹ C, q = n·e, and total charge is conserved in isolated systems. Loss of electrons produces positive charge, and number of transferred electrons follows n = q/e, linking macroscopic charge measurement to microscopic carriers. Let x be distance from +10 μC , then 0.8 - x from -2 μC . (10 × 10⁻⁶/x²) = (2 × 10⁻⁶/(0.8 - x)²) , 10 (0.8 - x)² = 2 x² . 5 (0.64 - 1.6 x + x²) = x² , 3.2 - 8 x + 5 x² = x² . 4 x²

Ref: NCERT > Physics Book > Electric Charges and Fields > Electric Charge, Quantization and Conservation

An infinite line charge has \( E = 6.3 \times 10^5 \, \text{N/C} \) at 7 cm. What is \( \lambda \)?

**Fundamental property of charge** includes additivity and quantization, meaning net charge equals algebraic sum of constituents and each is multiple of e. When rod loses charge, electron removal is inferred, and n = q/e gives transferred count. E = (2 k λ/r) . 6.3 × 10⁵ = (2 × 9 × 10⁹ × λ/0.07) . λ = (6.3 × 10⁵ × 0.07/18 × 10⁹) = 2.45 × 10⁻⁶ C/m . Substituting values gives 2.45 × 10⁻⁶ C/m, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

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A point charge \( 10 \, \mu\text{C} \) is at the origin. What is the electric field magnitude at a point 5 m along the z

**Charge conservation and quantization** govern rubbing processes where electrons transfer without creation. Total charge before and after remains equal, and any measured charge corresponds to n = q/e electrons, allowing counting of carriers from coulomb value. E = (k |q|/r²) . k = 9 × 10⁹ N·m²/C² , q = 10 × 10⁻⁶ C , r = 5 m . E = 9 × 10⁹ × (10 × 10⁻⁶/(5)²) = 9 × 10⁹ × (10 × 10⁻⁶/25) = 3.6 × 10³ N/C . Substituting values gives 3.6 × 10³ N/C, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

Ref: NCERT > Physics Book > Electric Charges and Fields > Electric Charge, Quantization and Conservation

Two charges \( +2 \, \mu\text{C} \) and \( +3 \, \mu\text{C} \) are 10 cm apart. What is the electric field at a point 5

**Charge conservation and quantization** govern rubbing processes where electrons transfer without creation. Total charge before and after remains equal, and any measured charge corresponds to n = q/e electrons, allowing counting of carriers from coulomb value. Distance from +3 μC = 5 cm. E₁ = 9 × 10⁹ × (2 × 10⁻⁶/(0.05)²) = 7.2 × 10⁶ N/C (away). E₂ = 9 × 10⁹ × (3 × 10⁻⁶/(0.05)²) = 1.08 × 10⁷ N/C (towards). Net E = 1.08 × 10⁷ - 7.2 × 10⁶ = 3.6 × 10⁶ N/C (towards +3 μC ). Substituting values gives 3.6 × 10⁶ N/C, which matches expected magnitude for this

Ref: NCERT > Physics Book > Electric Charges and Fields > Electric Charge, Quantization and Conservation

A point charge \( -6 \, \mu\text{C} \) is at the origin. What is the electric field magnitude at a point 3 m along the y

**Quantization of charge** states observable charge is integer multiple of elementary charge e = 1.6×10⁻¹⁹ C, q = n·e, and total charge is conserved in isolated systems. Loss of electrons produces positive charge, and number of transferred electrons follows n = q/e, linking macroscopic charge measurement to microscopic carriers. E = (k |q|/r²) . k = 9 × 10⁹ N·m²/C² , q = 6 × 10⁻⁶ C , r = 3 m . E = 9 × 10⁹ × (6 × 10⁻⁶/(3)²) = 9 × 10⁹ × (6 × 10⁻⁶/9) = 6 × 10³ N/C . Substituting values gives 6 × 10³ N/C, which matches

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What ensures that the electric field lines from a negative charge always terminate on it rather than extend to infinity?

**Fundamental property of charge** includes additivity and quantization, meaning net charge equals algebraic sum of constituents and each is multiple of e. When rod loses charge, electron removal is inferred, and n = q/e gives transferred count. Negative charges attract positive test charges, so field lines, representing the force direction on a positive charge, point inward toward the negative charge. This attraction defines their termination, unlike positive charges where lines extend outward. Substituting values gives Attraction, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

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What property of electric charges allows them to be treated as scalars despite their ability to attract or repel?

**Charge conservation and quantization** govern rubbing processes where electrons transfer without creation. Total charge before and after remains equal, and any measured charge corresponds to n = q/e electrons, allowing counting of carriers from coulomb value. The additivity of charges means their total value is the algebraic sum of individual charges, treating them as scalars with magnitude and sign (positive or negative). The directional forces (attraction/repulsion) arise from field interactions, not the charge itself. Substituting values gives Additivity, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

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An infinite line charge has \( \lambda = 3 \times 10^{-6} \, \text{C/m} \). What is the electric field at 15 cm?

**Quantization of charge** states observable charge is integer multiple of elementary charge e = 1.6×10⁻¹⁹ C, q = n·e, and total charge is conserved in isolated systems. Loss of electrons produces positive charge, and number of transferred electrons follows n = q/e, linking macroscopic charge measurement to microscopic carriers. E = (2 k λ/r) , k = 9 × 10⁹ N·m²/C² . E = (2 × 9 × 10⁹ × 3 × 10⁻⁶/0.15) = 3.6 × 10⁵ N/C . Substituting values gives 3.6 × 10⁵ N/C, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

Ref: NCERT > Physics Book > Electric Charges and Fields > Electric Charge, Quantization and Conservation

A point charge \( 12 \, \mu\text{C} \) is at the origin. What is the electric field magnitude at a point 8 m along the x

**Fundamental property of charge** includes additivity and quantization, meaning net charge equals algebraic sum of constituents and each is multiple of e. When rod loses charge, electron removal is inferred, and n = q/e gives transferred count. E = (k |q|/r²) . k = 9 × 10⁹ N·m²/C² , q = 12 × 10⁻⁶ C , r = 8 m . E = 9 × 10⁹ × (12 × 10⁻⁶/(8)²) = 9 × 10⁹ × (12 × 10⁻⁶/64) = 1.6875 × 10³ N/C . Substituting values gives 1.69 × 10³ N/C, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

Ref: NCERT > Physics Book > Electric Charges and Fields > Electric Charge, Quantization and Conservation

Two charges \( +6 \, \mu\text{C} \) and \( -3 \, \mu\text{C} \) are 50 cm apart. What is the electric field magnitude at

**Quantization of charge** states observable charge is integer multiple of elementary charge e = 1.6×10⁻¹⁹ C, q = n·e, and total charge is conserved in isolated systems. Loss of electrons produces positive charge, and number of transferred electrons follows n = q/e, linking macroscopic charge measurement to microscopic carriers. Midpoint distance = 25 cm = 0.25 m. E₁ = 9 × 10⁹ × (6 × 10⁻⁶/(0.25)²) = 8.64 × 10⁵ N/C (towards -3 μC ). E₂ = 9 × 10⁹ × (3 × 10⁻⁶/(0.25)²) = 4.32 × 10⁵ N/C (towards -3 μC ). Net E = 8.64 × 10⁵ + 4.32 × 10⁵ = 1.296

Ref: NCERT > Physics Book > Electric Charges and Fields > Electric Charge, Quantization and Conservation