Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
COMEDK2025PhysicsElectrostaticsActual

The magnitude and direction of the electric field in a particular region is (10 i +4 j +2 k ) 10^4 NC ⁻¹ . What s the electric flux through an area (3 i - k ) 10⁻² ~m ^2

Options

  1. A1.4 10^3 Nm ^2 C ⁻¹
  2. B2.8 10^3 Nm ^2 C ⁻¹
  3. C2.8 Nm ^2 C ⁻¹
  4. D2.8 10^2 Nm ^2 C ⁻¹

Correct answer

B. 2.8 10^3 Nm ^2 C ⁻¹

Step-by-step solution

The electric flux _E through a surface is given by the dot product of the electric field vector E and the area vector A . Given E = (10 i + 4 j + 2 k ) 10^4 NC ⁻¹ and A = (3 i - k ) 10⁻² m ^2 . The flux is calculated as _E = E A . Substituting the vectors: _E = [(10 i + 4 j + 2 k ) 10^4] [(3 i + 0 j - 1 k ) 10⁻²] _E = (10^4 10⁻²) [(10 i + 4 j + 2 k ) (3 i + 0 j - 1 k )] _E = 10^2 [(10 3) + (4 0) + (2 -1)] _E = 100 [30 + 0 - 2] _E = 100 28 = 2800 Nm ^2 C ⁻¹ Expressing in scientific notation, _E = 2.8 10^3 Nm ^2 C ⁻¹

Practice Electrostatics on Quantrex Academy →

More from Electrostatics

A charge of 5 C is placed at the centre of a spherical shell S₁ of radius 10 cm. Now this system is enclosed inside another spherical shell S₂ of radius 20 cm. The ratio of the ele 2026Two point charges P = +25 C and Q = -16 C are placed 5 cm apart. Find the position of the point at which the resultant electric field is zero: 2026Bodies P, Q, R, S are labelled as having charges Q_P = 0.5 10⁻¹⁹C , Q_Q = 0.7 10⁻¹⁹C , Q_R = 2.1 10⁻¹⁹C , Q_S = 4.8 10⁻¹⁹C respectively. Select the body having the correct charge. 2026Uniform electric field of 5 10^3 ,NC⁻¹ is maintained in the positive Y direction. Now a point charge of 2 10⁻⁴C at rest is released from the origin. The kinetic energy attained by 2026A pith ball of mass 'm' gram and charge 'Q' is suspended using a mass less silk thread near a large charged conducting metal sheet of area 'A' and surface charged density ' '. If t 2026In a uniform electric field 10^6 N C⁻¹ an electric dipole of length 4 cm is placed with its axis making an angle 60^ with the electric field. If the dipole experiences a torque of 2026An electric field and magnetic field 1.8 10^4 Vm⁻¹ and 6 10⁻³ T respectively are applied simultaneously on an electron beam such that path of the beam remains undeviated, then the 2026A uniform electric field E = 3 i + 6 j + k passes through a closed cuboidal surface. One face of the cuboid has an area 4 m^2 and an outward unit normal given by 2 i +2 j +3 k 17 . 2026 Full Electrostatics list All COMEDK PYQs