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Flashcards in Electrostatics. Deck (33):
1

What is charge q in terms of number of electrons e ?

q=ne

2

Coulumbs Law

F= k q1q2/ r^.
k=1/4πε₀
unit of k = N metre square per coulomb square
k= 9 x 10^9
ε₀= 8 x 10^-12

3

Unit of k in electrostatics Coulomb's law

N m^ c^-2

4

Unit of ε₀ (permittivity of free space )

C^/N m^-2

5

Field strength due to a point charge

E= k q/r^

6

Direction of field strength due to positive and negative charge ?

Due to positive charge field strength is away from the charge and due to negative charge field strength is towards the charge.

7

Electric potential V due to point charge

V= k q/r

8

Electrostatic potential energy U of two point charges.

U= k q1q2/r

9

What is electrostatic potential energy in terms of charge and electrostatic potential ?

U= qV

10

Potential difference in an uniform electric field?

In an indoors electric field , potential difference V= Ed

11

Formula of electric dipole

p=q(2a). Direction of p vector is from -q to +q

12

Electric field strength E for a uniformly charged spherical shell

E(i)=0
E(s)=k q/R^= σ/ε₀
Eo= kq/r^

13

Electric field strength e for a solid sphere of charge.

E(i)=Kqr/R³
E(s)=Kq/R^
Eo=Kq/r^

14

Electric field strength E on the axis of a uniformly charged ring

E= Kqx÷(R²+x²)^3/2
At centre , x= 0 and hence E=0

15

Electric field Strength E for a infinitely long line charge

E= λ/2πε₀r

16

Electric potential V for a uniformly charged spherical shell

V(i) = V(s) = Kq/R=σR/ε₀
Vo=Kq/r

17

Electric Potential for a solid sphere of charge

V(i)= Kq÷R³(1.5 R² - 0.5 r²)
V(s)=Kq/R
Vo=Kq/r

18

Electric potential on the axis of a uniformly charged ring

V=Kq÷√R²+x²
At centre ,
x=0
V= Kq/R

19

Electric Potential V for an infinitely long line charge

PD= λ÷2πε₀ ln (r₂/r₁)

20

Torque due to an electric dipole when placed in an uniform electric field

Torque = pE sin #

21

Electric potential energy U due to an electric dipole when placed in a uniform electric field

U=-PE= -pE cos#

22

When an electric dipole is placed in an uniform electric field , what happens when #=0?

In #=0 , it's a stable equilibrium position.
In this position , F=0
Torque =0
U=-p.E= minimum

23

When an electric dipole is placed in an uniform electric field , what happens when #=180?

#=0 is unstable equilibrium position. In this F=0 and torque = 0 but U= +p.E= maximum.

24

Electric flux on surface formula ?

∫∞=∫E . dS

25

Mathematically , what is Gauss Law?

∫E . dS= q(in) / ε₀
or 'Electric Flux from a closed surface'= q(in) / ε₀

26

Electric filed due to a plane sheet of charge

E=σ/2 ε₀

27

What is electric field on the surface of any charged conducting body ?

E=σ/ε₀

28

Electric filed of a conductor under electrostatic conditions?

E(i)= 0
E(s) = σ/ε₀

29

What are the two properties of a conductor regarding electric field lines and electric potential.

1.On the surface of charged conductor electric lines are perpendicular to the surface
2. The potential of charged conductor through out its volume is same.

30

Potential difference between two charged spherical shells

V1-V2=q1÷4πε₀(1/r1-1/r2)

31

What is charge per unit length λ?

It's charge distribution along a line.
dq = λ dx

32

What is charge per unit area σ?

It's charge distribution on the surface.
dq= σ dA

33

What is charge per unit volume p?

It's charge distribution throughout a volume.
dq= p dV