Electric Charges and Fields

34 solved questions from Class 12 Physics, each with the full working. Tap any question to see the step-by-step solution.

• 1 What is the fundamental law or governing principle of 'Electric Charges and Fields' in Class 12 Physics? medium MCQ Fundamental Physical Law
• 2 What is the SI unit and dimensional formula for the key physical quantity studied in 'Electric Charges and Fields'? medium MCQ SI Units & Dimensional Analysis
• 3 How does the field or potential intensity vary with distance r in 'Electric Charges and Fields'? medium MCQ Spatial Distance Dependence
• 4 What is the net flux or circulation integral through a closed surface in 'Electric Charges and Fields'? medium MCQ Gauss's Theorem & Boundary Integrals
• 5 Why do field lines in 'Electric Charges and Fields' never intersect each other? medium MCQ Field Line Properties
• 6 A cube of side 0.4 m is placed in an electric field whose magnitude varies linearly with position: E_x=150,x N/C, where x is measured in metres from the left face of the cube. The cube’s faces are parallel to the coordinate axes and the left face is at x=0. Find the net electric flux through the cube. hard 5 marks Divergence theorem for non‑uniform field
• 7 Explain why electric field lines of a static electric field never intersect each other. easy 1 mark Field line non‑intersection principle
• 8 Three point charges of +2 µC, –3 µC and +1 µC are placed at the vertices of an equilateral triangle of side 0.2 m. A spherical Gaussian surface of radius 0.25 m centered at the triangle’s centroid encloses all three charges. Calculate the net electric flux through the surface. medium 3 marks Gauss’s law for net flux
• 9 What is the SI unit of electric field? easy 1 mark SI unit of electric field
• 10 A cube of side 0.50,m is placed in a uniform electric field of magnitude 2000,N/C directed along the +z axis. What is the net electric flux through the cube? easy MCQ 1 mark Flux through cube in uniform field
• 11 A long cylindrical shell of radius a=0.10,m carries a uniform surface charge density σ=5.0,μC/m^2. A coaxial cylindrical Gaussian surface of radius r=0.20,m is drawn outside the shell. Calculate the electric flux through this Gaussian surface per unit length of the cylinder. hard 4 marks Gauss's law for cylindrical shell
• 12 Two parallel plates of area 0.02 m² carry charges +Q and –Q respectively, with Q=4 nC. Find the magnitude of the electric field between the plates. medium 2 marks Electric field between parallel plates
• 13 A point charge of +5 µC is placed at the origin. Find the magnitude of the electric field at a point that lies on the y‑axis 0.30 m away from the origin. easy 1 mark Electric field of point charge
• 14 An infinitely long straight line carries a uniform linear charge density λ = 2 μC/m. Find the magnitude of the electric field at a point 5 cm away from the line. hard 3 marks Electric field of an infinite line charge
• 15 A solid insulating cylinder of radius a=4.0 cm carries a uniform volume charge density ρ = 5.0×10^-6 C/m^3. Determine the magnitude of the electric field (a) at a point r=2.0 cm from the axis (inside the cylinder) and (b) at a point r=6.0 cm from the axis (outside the cylinder). State the direction of the field in each case. hard 4 marks Gauss's law for volume charge distribution
• 16 A spherical surface of radius 0.10 m is placed in a uniform electric field of magnitude 3.0×10^4 N/C directed along the +x direction. What is the net electric flux through the spherical surface? medium MCQ 2 marks Gauss's law – net flux
• 17 A point charge of +8 μC is placed at the origin. Find the magnitude of the electric field at the point (0,0,0.40 m). easy 1 mark Electric field of a point charge
• 18 A point charge of +5 µC is placed at the origin. Find the magnitude of the electric field at the point (0.12 m, 0, 0) on the x–axis. medium 3 marks Electric field of a point charge
• 19 Two parallel plates of area 0.01 m² are separated by 4 mm. They carry charges +6 nC and –6 nC respectively. Find the magnitude of the electric field between the plates. medium 4 marks Electric field between parallel plates
• 20 A cube of side 0.20 m is placed in a uniform electric field of magnitude 500 N/C directed along the +y–axis. What is the net electric flux through the cube? easy MCQ 2 marks Gauss’s law – net flux through closed surface with no enclosed charge
• 21 A solid sphere of radius 0.05 m carries a uniform volume charge density ρ=3.0×10⁻⁶ C/m³. Find the magnitude of the electric field at a point 0.08 m from the center (outside the sphere). hard 5 marks Gauss's law – field outside uniformly charged sphere
• 22 A point charge of +3 µC is placed at the origin. Find the magnitude of the electric field at the point (0.25 m, 0, 0) on the x–axis. easy 2 marks Electric field of a point charge
• 23 A cube of side 0.15 m is placed in a uniform electric field of magnitude 400 N/C directed along the +z–axis. What is the net electric flux through the cube? medium 3 marks Electric flux through a closed surface
• 24 An infinitely long straight line carries a uniform linear charge density λ = 4 μC/m. Find the magnitude of the electric field at a point 3 cm away from the line. hard 5 marks Electric field of an infinite line charge
• 25 A solid sphere of radius 0.10 m carries a uniform volume charge density ρ=2.0×10^-5 C/m^3. Find the magnitude of the electric field at a point 0.08 m from the center (inside the sphere). hard 4 marks Gauss's law for symmetric charge distributions
• 26 A point charge of +2;μC is placed at the origin. What is the magnitude of the electric field at a point 0.5 m on the y‑axis? easy MCQ 1 mark Electric field of a point charge
• 27 An infinitely long cylindrical shell of radius a = 5.0 cm carries a uniform surface charge density σ = 2.0 μC/m^2. Using Gauss's law, (a) derive the expression for the electric field both inside (r<a) and outside (r>a) the shell, and (b) calculate the magnitude of the field at r = 3.0 cm and r = 8.0 cm. hard 4 marks Gauss's law for cylindrical symmetry
• 28 A point charge of +1 μC is placed at the origin. Calculate the magnitude of the electric field at the point P located 0.20 m on the positive z‑axis. easy 1 mark Electric field of a point charge
• 29 Two infinitely long parallel line charges are 4.0 cm apart. Line 1 carries λ_1=+3 μC/m and line 2 carries λ_2=-3 μC/m. Find the magnitude of the resultant electric field at the point midway between the two lines. hard 3 marks Superposition of fields from line charges
• 30 A uniform electric field of magnitude 600 N/C lies in the xy‑plane making an angle 30° with the positive x‑axis. A square of side 0.10 m lies in the xy‑plane with its normal along the +z direction. What is the electric flux through the square? medium MCQ 2 marks Electric flux through a surface
• 31 An electric dipole has charges of +5.0 μC and -5.0 μC separated by 5.0 cm. (a) Calculate the magnitude of the electric dipole moment. (b) Find the magnitude of the electric field at a point on the axial line of the dipole, 0.40 m from the dipole centre. Use 1/4πε_0=9.0×10^9 N·m^2/C^2. (For a dipole with p ≪ r^2, the axial field is E=1/4πε_02p/r^3.) medium 4 marks Dipole moment and axial electric field
• 32 A point charge of +2,μC is placed at the origin. What is the magnitude of the electric field at a point that lies 0.15;m away from the charge? easy 2 marks Electric field of a point charge
• 33 A solid sphere of radius 0.05 m is uniformly charged with a volume charge density ρ=1.0×10^-5 C/m^3. Calculate the magnitude of the electric field at a point 0.08 m from the centre of the sphere (outside the sphere). hard 5 marks Electric field outside a uniformly charged sphere
• 34 A cube of side 0.20 m is placed in a non‑uniform electric field that varies linearly with the vertical coordinate: E_z = 5000,z N/C, where z is measured in metres from the cube’s bottom face. The cube’s faces are perpendicular to the coordinate axes. What is the net electric flux through the cube? hard MCQ 4 marks Flux through a surface in a varying field