FAQ (Frequently Asked Questions)
You can jot down all the important formulae at one place so that you can glance through them whenever you have some free time. This is also another way to revise and memorise all the formulae.
1) Per unit length (linear charge density),
2) Per unit area (surface charge density),
3) Per unit volume (volume charge density)
Charge density depends on the charge distribution and it can be positive or negative. Depending on nature, charge density formula can be given by,
- Linear Charge Density:
λ = q / l, where q is the charge and l is the length over which it is distributed. The SI unit is (Coulomb) Cm–1.
- Surface Charge Density:
σ = q / A, where, q is the charge and A is the area of the surface. The SI unit is (Coulomb) Cm–2.
- Volume Charge Density:
ρ = q / v, where q is the charge and V is the volume of distribution. The SI unit is (Coulomb) Cm–3.
[Where W = work done, g = acceleration due to gravity, h = height of free fall
If the angle between gravitational force and direction of motion is 𝚹, then work done due to gravity is given by, W = mgh cos 𝚹
So if an object is moving in a horizontal direction on the surface of the earth, then work done by gravity is ‘zero’.