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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. Infinitely long uniformly charged line
Explanation: Step 1: Cylindrical symmetry has a long axis. Step 2: An infinitely long uniformly charged line has this symmetry around it. Step 3: Choose a cylindrical Gaussian surface for such cases.
Correct answer: A. Infinite uniformly charged plane sheet
Explanation: Step 1: Plane symmetry means the surface is very large and uniformly spread. Step 2: An infinite uniformly charged sheet is the ideal example. Step 3: A pillbox Gaussian surface is useful here.
Correct answer: A. Like the same total charge placed at the centre
Explanation: Step 1: A spherical shell has spherical symmetry. Step 2: A Gaussian sphere outside encloses the whole charge. Step 3: Hence the outside field behaves like that of a point charge at the centre.
Correct answer: A. Zero
Explanation: Step 1: Charge of a spherical shell lies on its surface. Step 2: A Gaussian surface inside the shell encloses no charge. Step 3: Therefore the enclosed charge is zero.
Correct answer: A. Electric field in the cavity is zero
Explanation: Step 1: In electrostatic equilibrium, field inside the conducting material is zero. Step 2: If there is no charge in the cavity, there is no source inside it. Step 3: Hence field in the cavity is zero.
Correct answer: A. Positive
Explanation: Step 1: Field lines leaving the surface give positive outward flux. Step 2: If more lines leave than enter, total flux is positive. Step 3: Therefore net enclosed charge is positive.
Correct answer: A. Negative
Explanation: Step 1: Lines entering the surface give negative contribution to outward flux. Step 2: If entering lines are more, total flux is negative. Step 3: Therefore net enclosed charge is negative.
Correct answer: A. Zero
Explanation: Step 1: Entering lines give negative flux. Step 2: Leaving lines give positive flux. Step 3: If both are equal, total flux and enclosed charge are zero.
Correct answer: A. Where charge distribution is simple and symmetric
Explanation: Step 1: Gauss's law is a general law. Step 2: Its direct use is easiest when good symmetry exists. Step 3: In school-level problems, identifying symmetry is the first step.
Correct answer: A. Stronger
Explanation: Step 1: Field near a conductor surface is related to surface charge density. Step 2: Larger surface charge density indicates stronger field. Step 3: Remember the direct relation between surface charge and field.
Correct answer: A. Spherical, cylindrical, and plane
Explanation: Step 1: Symmetry is very important in Gauss's law calculations. Step 2: Point or sphere gives spherical, line gives cylindrical, and sheet gives plane symmetry. Step 3: Identify the symmetry type quickly while reading the question.
