Electricity and Magnetism Answers

Point charges are placed at the vertices of a square of side L as shown in figure. what should be sign of charge q and magnitude of the ratio |q/Q| so that

(a) net force on each Q is zero?

(b) net force on each q is zero?

(c) Is it possible that the entire system could be in electrostatic equilibrium?

The electric field in a region is given by Ē = 20î + 30ĵ in certain units. As one goes a small distance dl in the direction of ñ = 30î - 20ĵ , the potential will :-

(a) increase

(b) decrease

(c) remain constant

(d) change sign

(Note:- This question have one or more than one correct choice(s) out of the four given choices. Any number of options may be correct.)

Consider three charge distributions
A. ρ (x, y, z) = kx

B. ρ (x, y, z) = k √ (x2 + y2)

C. ρ (x, y, z) = k √ (x2 + y2 + z2)

Here k is a constant. A, B, C are

(a) Planar Symmetric

(b) Planar, Spherically, Cylindrically Symmetric respectively

(c) Spherically, Planar and cylindrically symmetric respectively

(d) Planar, Cylindrically, Spherically symmetric respectively

If the z-axis is vertical and r̂, θ̂^ and φ̂ are unit vectors in spherical coordinates (standard symbols)


(a) r̂ is always horizontal

(b) θ̂^ is always horizontal

(c) φ̂ is always horizontal

(d) θ̂^ can be vertical

[Note:- This question have one or more than one correct choice(s) out of the four given choices. Any number of options may be correct.]

If the z-axis is vertical and ŝ, φ̂, ẑ are unit vectors in cylindrical coordinates (standard symbols),

(a) ŝ is horizontal

(b) φ̂ is horizontal

(c) φ̂ is vertical

(d) ŝ is vertical

(Note:- This question have one or more than one correct choice(s) out of the four given choices. Any number of options may be correct.)

The direction of the gradient of a scalar field V gives the direction in which

(a) V increases at the highest rate

(b) V decreases at the highest rate

(c) V remains constant for small distances

(d) V changes its sign

(Note:- This question have one or more than one correct choice(s) out of the four given choices. Any number of options may be correct.)

The electric field in an electrostatic situation is denoted by the function E and the potential by the function V in a certain volume. Inside this volume,

(a) If E is given, V can be uniquely written.

(b) If V is given, E can be uniquely written.

(c) If E is same everywhere in the volume, V cannot change in this volume.

(d) If V is same everywhere in the volume, E cannot change in this volume.

(Note:- This question have one or more than one correct choice(s) out of the four given choices. Any number of options may be correct.)

an electron is stationary in electric field 0.8 V/m find Lorenz force on it.

what is electric charge.