Class 12 Electric Charges And Fields CBSE Questions & Answers

Two equal positive charges q1 = q2 = 2.0 \(\mu {\rm{C}}\) are located at x = 0, y =0.3 and x =0 and y = -0.3 m respectively. What are the magnitude and direction of the total electric force (expressed in Newton and degrees counter clockwise w.r.t x - axis) that q1 and q2 exert on a third charge Q = 4.0 \(\mu {\rm{C}}\) at x =0.4 and y = 0 m

Positive and negative point charges of equal magnitude are kept at ( 0,0,a/2) and (0,0,-a/2) respectively. The work done by the electric field when another positive point charge is moved from (-a,0,0) to (0,a,0) is

A disk of radius a/4 having a uniformly distributed charge 6C is placed in the x-y plane with its centre at (−a/2, 0, 0). A rod of length a carrying a uniformly distributed charge 8C is placed on the x-axis from x = a/4 to x = 5a/4. Two point charges −7C and 3C are placed at (a/4, −a/4, 0) and (−3a/4, 3a/4, 0), respectively. Consider a cubical surface formed by six surfaces \({\rm{x }} = {\rm{ }} \pm {\rm{ a}}/{\rm{2}},{\rm{ y }} = {\rm{ }} \pm {\rm{ a}}/{\rm{2}},{\rm{ z }} = {\rm{ }} \pm {\rm{ a}}/{\rm{2}}\). The electric flux through this cubical surface is

Three concentric metallic spherical shells of radii R, 2R, 3R, are given charges Q1, Q2, Q3, respectively. It is found that the surface charge densities on the outer surfaces of the shells are equal. Then, the ratio of the charges given to the shells, Q1: Q2: Q3, is

Under the influence of the coulomb field of charge +Q, a charge −q is moving around it in an elliptical orbit. Find out the correct statement(s).

Consider a system of three charges \(\frac{q}{3} , \frac{q}{3} and -\frac{2q}{3} \) placed at points A, B and C, respectively, as shown in the figure. Take O to be the centre of the circle of radius R and angle CAB = \({\rm{6}}0^\circ \)

An oil drop of 12 excess electrons is held stationary under a constant electric field of \({\rm{2}}.{\rm{55 }} \times {\rm{ 1}}{0_{\rm{4}}}{\rm{N}}{{\rm{C}}_{ - {\rm{1}}}}\) in Millikan’s oil drop experiment. The density of the oil is 1.26 g cm-3. Estimate the radius of the drop. (g = 9.81 m \({{\rm{s}}^{ - {\rm{2}}}}\); e = 1.60 × 10–19 C).

A point charge q = -8.0 nC is located at the origin. Magnitude of the electric field vector at the field point x = 0.949m y = -1.643m is

If two electrons are each \({\rm{1}}.{\rm{5}}0{\rm{ }} \times {\rm{ 1}}{0_{ - {\rm{1}}0}}{\rm{m}}\) from a proton, as shown in Figure , magnitude of the net electric force they will exert on the proton is

A point charge Q is moved along a circular path around another fixed point charge The work done is zero

In a regular polygon of n sides, each corner is at a distance of r from the center. Identical charges of magnitude Q are placed at (n -1) corners. The field at the center is

A half ring of radius R has a charge of \(\lambda \) per unit length. The field at the center is

Which of the following is not true for a region with uniform electric field?

A charge Q is placed at the mouth of a conical flask. The flux of the electric field through the flask is

A long string of charge \(\lambda \) per unit length passes through an imaginary cube of edge a. The maximum flux of the electric field will be