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SubjectsPhysics
गाउस का नियम और इसके अनुप्रयोग
In this Class 12 Physics topic from Chapter 1, Electric Charges and Fields, students learn how electric flux is related to the net charge enclosed by a closed surface through Gauss’s law. The topic develops the idea of Gaussian surfaces, uses symmetry to simplify electric-field calculations, and applies the law to charged spherical shells, uniformly charged spheres, infinite line charges, and plane sheets. It also helps students understand the electric field inside conductors and choose suitable surfaces for solving electrostatic problems.
Correct answer: A. Zero
Explanation: Step 1: Inside a conductor in electrostatic equilibrium, electric field is zero. Step 2: So total flux through a Gaussian surface inside it is zero. Step 3: Hence net enclosed charge is zero.
Correct answer: A. As if the whole charge is at the centre
Explanation: Step 1: A spherical conductor has spherical symmetry. Step 2: For outside points, its field behaves as if the whole charge were concentrated at the centre. Step 3: Treat it like a point charge for outside field.
Correct answer: A. Zero
Explanation: Step 1: Take a Gaussian surface inside the spherical shell with no charge enclosed. Step 2: Since enclosed charge is zero, total flux is zero. Step 3: By symmetry, the electric field inside is zero.
Correct answer: A. It is independent of distance
Explanation: Step 1: An infinite plane sheet has plane symmetry. Step 2: From Gauss's law, the field does not depend on distance. Step 3: Remember this for the ideal infinite sheet model.
Correct answer: A. Radially outward or inward from the line
Explanation: Step 1: A long charged line has cylindrical symmetry. Step 2: The field is perpendicular to the line in radial direction. Step 3: For positive line charge it is outward and for negative line charge inward.
Correct answer: A. It decreases inversely with distance
Explanation: Step 1: For an infinite line charge, a cylindrical Gaussian surface is used. Step 2: From Gauss's law, the field varies inversely with distance. Step 3: Remember line charge and point charge have different distance dependence.
Correct answer: A. Perpendicular to the surface
Explanation: Step 1: In electrostatic equilibrium, tangential field cannot exist on a conductor surface. Step 2: If it existed, charges would move along the surface. Step 3: Hence the field is perpendicular to the surface.
Correct answer: A. Coulomb's law
Explanation: Step 1: Gauss's law relates charge and electric field in electrostatics. Step 2: It is consistent with Coulomb's law and can be understood from it. Step 3: Do not confuse it with current or heat laws.
Correct answer: A. Newton metre squared per coulomb
Explanation: Step 1: Electric flux is related to electric field and area. Step 2: Electric field has unit newton per coulomb and area has metre squared. Step 3: So flux has unit newton metre squared per coulomb.
Correct answer: A. Double
Explanation: Step 1: In Gauss's law, total flux is proportional to enclosed charge. Step 2: Doubling the charge doubles the net source. Step 3: Therefore total flux doubles.
Correct answer: A. Symmetry of charge distribution
Explanation: Step 1: A Gaussian surface is chosen to simplify calculation. Step 2: A good surface matches the symmetry of charge distribution. Step 3: Identify spherical, cylindrical, and plane symmetry separately.
Correct answer: A. Because total flux is decided by net enclosed charge
Explanation: Step 1: By Gauss's law, total flux through a closed surface depends on enclosed charge. Step 2: Changing area or shape may change local field. Step 3: But if enclosed charge is same, total flux remains same.
Correct answer: A. Zero
Explanation: Step 1: Total flux depends on net enclosed charge. Step 2: Two equal positive and two equal negative charges make net charge zero. Step 3: Therefore total flux is zero.
Correct answer: A. Coulomb's law
Explanation: Step 1: A point charge has spherical symmetry. Step 2: Applying Gauss's law gives the same distance dependence as Coulomb's law. Step 3: Thus both are connected in electrostatics.
Correct answer: A. Perpendicular to the sheet
Explanation: Step 1: A plane sheet has plane symmetry. Step 2: The field is perpendicular to the sheet. Step 3: For a positive sheet it points away, and for a negative sheet it points toward the sheet.
Correct answer: A. Away from the sheet
Explanation: Step 1: Field lines emerge outward from positive charge. Step 2: An infinite sheet has the same symmetry on both sides. Step 3: Therefore the field points away from the sheet on both sides.
Correct answer: A. Toward the sheet
Explanation: Step 1: Field lines go toward negative charge. Step 2: Symmetry is same on both sides of an infinite sheet. Step 3: Hence the field points toward the sheet on both sides.
Correct answer: A. Inversely proportional to distance
Explanation: Step 1: A line charge has cylindrical symmetry. Step 2: Gauss's law gives field inversely proportional to distance. Step 3: Remember it separately from inverse-square point charge field.
Correct answer: A. Inversely proportional to square of distance
Explanation: Step 1: A point charge has spherical symmetry. Step 2: Gauss's law gives its field inversely proportional to square of distance. Step 3: Compare this with line charge and sheet results.
Correct answer: A. Due to plane symmetry
Explanation: Step 1: An infinite sheet looks symmetric at every point. Step 2: In Gauss's law calculation, distance dependence does not remain. Step 3: This result applies to the ideal infinite sheet.
Correct answer: A. Net enclosed charge is zero
Explanation: Step 1: Total flux is linked to enclosed charge. Step 2: If total flux is zero, net enclosed charge is zero. Step 3: This does not mean field is zero everywhere on the surface.
Correct answer: A. Electric field of symmetric charge distributions
Explanation: Step 1: Gauss's law relates charge and electric field. Step 2: It is especially useful for finding fields of symmetric distributions. Step 3: For non-symmetric cases, the law is true but calculation may be difficult.
Correct answer: A. Zero
Explanation: Step 1: In Gauss's law, total flux is decided only by enclosed charge. Step 2: An outside positive charge may create field on the surface. Step 3: But with no enclosed charge, total flux is zero.
Correct answer: A. No, it can be imaginary
Explanation: Step 1: A Gaussian surface is chosen for calculation. Step 2: It need not be a real object. Step 3: It is commonly imagined according to symmetry.
Correct answer: A. Radial
Explanation: Step 1: In spherical symmetry, all directions are related to the centre equally. Step 2: Therefore field is radial outward or inward. Step 3: For positive charge it is outward and for negative inward.
