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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. Net enclosed charge is negative
Explanation: Step 1: Sign of total flux is linked with sign of net enclosed charge. Step 2: Negative total flux indicates negative net enclosed charge. Step 3: Look at the sign of total flux, not just local field direction.
Correct answer: A. Positive
Explanation: Step 1: In Gauss's law, total flux is proportional to net enclosed charge. Step 2: Positive flux means net enclosed charge is positive. Step 3: Do not be confused by field direction at only one part of the surface.
Correct answer: A. Positive
Explanation: Step 1: Take algebraic sum of enclosed charges. Step 2: Two positive charges and one equal negative charge leave a positive net charge. Step 3: Therefore total flux is positive.
Correct answer: A. Zero
Explanation: Step 1: Take algebraic sum of charges inside the closed surface. Step 2: Two equal positive and two equal negative charges give zero net charge. Step 3: Hence total flux is zero.
Correct answer: A. When charge distribution has no clear symmetry
Explanation: Step 1: Gauss's law is generally true. Step 2: To find field easily, symmetry is needed so that field becomes simple. Step 3: Without symmetry, the law is valid but calculation becomes difficult.
Correct answer: A. Total flux will not change
Explanation: Step 1: Total flux is determined by net enclosed charge. Step 2: The charge is inside the surface, whether at centre or not. Step 3: Thus total flux is same, though field distribution is not uniform.
Correct answer: A. Zero
Explanation: Step 1: In Gauss's law, only enclosed charge is counted. Step 2: The charge has moved outside, so enclosed net charge is zero. Step 3: Therefore total closed flux is zero.
Correct answer: A. Net enclosed charge is zero
Explanation: Step 1: If field is zero on the surface, flux through every part is zero. Step 2: By Gauss's law, zero total flux means net enclosed charge is zero. Step 3: Individual charges may exist inside, but net charge is zero.
Correct answer: A. No, positive and negative flux can cancel
Explanation: Step 1: Total flux is the algebraic sum over the whole closed surface. Step 2: Different parts may give positive and negative contributions. Step 3: Zero total flux does not mean field is zero everywhere.
Correct answer: A. Radially outward or inward from the line
Explanation: Step 1: A long line charge has cylindrical symmetry. Step 2: No special direction exists along the line, so field is radial. Step 3: For positive line it is outward and for negative line inward.
Correct answer: A. Perpendicularly away from the sheet
Explanation: Step 1: Field lines emerge from positive charge. Step 2: Symmetry of an infinite plane sheet makes field perpendicular to the sheet. Step 3: Therefore on both sides the field is away from the sheet.
Correct answer: A. Perpendicularly toward the sheet
Explanation: Step 1: Field lines terminate on negative charge. Step 2: For an infinite sheet, field is perpendicular to the plane. Step 3: Hence on both sides, the field points toward the negative sheet.
Correct answer: A. Electric field inside could not remain zero
Explanation: Step 1: If net charge were enclosed, Gauss's law would give non-zero flux. Step 2: Non-zero flux requires electric field on the surface. Step 3: Since field inside an electrostatic conductor is zero, net charge cannot be inside.
Correct answer: A. Because enclosed charge is defined for a closed surface
Explanation: Step 1: Gauss's law connects total flux with a closed surface. Step 2: For an open surface, inside and outside are not clearly defined. Step 3: Therefore Gaussian surface must be closed.
Correct answer: A. Zero degree
Explanation: Step 1: Field of a positive point charge is radially outward. Step 2: Area vector of a spherical surface is also radially outward. Step 3: Both are in the same direction, so the angle is zero degree.
Correct answer: A. One hundred eighty degrees
Explanation: Step 1: Field due to a negative charge points toward the centre. Step 2: The area vector of the closed spherical surface points outward. Step 3: They are opposite, so the angle is 180 degrees.
Correct answer: A. Yes, but finding field may be difficult
Explanation: Step 1: Gauss's law is valid for any closed surface. Step 2: If field is not uniform, calculating total flux is not simple. Step 3: So the law is valid, but application may be difficult.
Correct answer: A. Zero
Explanation: Step 1: For flux, field must cross the surface. Step 2: Field parallel to a surface does not cross it. Step 3: Therefore every contribution is zero and total flux is zero.
Correct answer: A. Zero
Explanation: Step 1: In electrostatic condition, electric field inside conductor material is zero. Step 2: Zero field gives zero total flux through the closed surface. Step 3: Therefore net charge enclosed by that Gaussian surface is zero.
Correct answer: A. Positive
Explanation: Step 1: Leaving field lines indicate positive flux. Step 2: More outgoing lines show positive total flux. Step 3: By Gauss's law, net enclosed charge is positive.
Correct answer: A. Negative
Explanation: Step 1: Entering field lines indicate negative flux. Step 2: More entry gives negative total flux. Step 3: Therefore net enclosed charge is negative.
Correct answer: A. Zero
Explanation: Step 1: Entry gives negative flux and exit gives positive flux. Step 2: If both are equal, total flux is zero. Step 3: By Gauss's law, net enclosed charge is zero.
Correct answer: A. Total positive contribution is greater than negative contribution
Explanation: Step 1: Total flux is algebraic sum over the whole closed surface. Step 2: Some parts may have local negative flux. Step 3: If positive contribution is greater, total flux remains positive.
Correct answer: A. Because entering and leaving contributions cancel
Explanation: Step 1: External charges can produce electric field on the surface. Step 2: Their field lines both enter and leave the closed surface. Step 3: Thus total flux can be zero while local field is non-zero.
Correct answer: A. Because surface charge density can be higher there
Explanation: Step 1: Charge on a conductor resides on its surface. Step 2: Near sharp parts, charge can be more concentrated. Step 3: Higher surface charge density gives stronger electric field nearby.
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