Electro Statics Flashcards
Charges, gausses law,volt , resistor
Origion
Word electrostatics mean?
Electro=charge
Statics=Rest
Charges in rest
Defination of electrostatics
the study of properties,behaviour and law related to charges at rest.
How many types of charges are there?
there are 2 kind of charges …
positive and negative.
Behaviour of similar charges to eachother?
they do repell eachother
Behaviour of different charges to one another?
they do attract eachother
like + and - attract eachother
the forces between charges are called?
Coloumb forces/electrostatic forces.
the law which tells about electrostatic force between charges is called?
Coloumb Law
Origion
Coloumb Law ?
given by coloumb in 1784
instrument used by coloumb for forces measurment btw charges
Torson Balance
Defination of coloumb Law:
Quantitative measure of electrostatic force
Equation of coloumb Law
F=K q1q2/r^2
value and def;
K in coloumb law is?
it is coloumb constant and its value is 9x10^9.
K=1/4pieE*
Value and defination
what is epsilon not E*?
it is the permitivity of free space. Air/vaccum.
it is the allowing of force between charges through vaccum medium.
E* =8.85x10^-12 Coloumb square/Newton meter square
Electrostatic force in permitivity of free space form
F=1/4pieE* q1q1/r^2
Unit,Defination,othernames
if there is medium except air between charges then ?
for another medium “Er” is used called relative permitivity or dielectric constant.
Er is unitless because it ration of forces.
Formula and Force when dielectric constant is::
formula of F for dielectric constant
F=1/4pieE*Er q1q2/r2
F is always less in dielectric than vaccum
the ratio one
another defination of Er
the ratio of Fin vaccum to F in medium……….Fvac/Fmed
Fvac >Fmed
What is electric field?
The region or space around any charge where electrostatic force can be felt. Or where charges repell or attract eachother.
What is Electric Intensity?
The amount/magnitude of electrosatic force felt by any test charge in electric field of point charge..
Defination of Electric intensity in mathematical form?
The force experienced per charge in field.
Formula for “E”?
E=F/q
Difference Btw pint charge and test charge.
Point charge is charge with big impact and is always positive.
Test Charge is less magnitude charge used for experiment
unit of Electric intensity?
- Unit Newton per coulumb(N/C)
- Volt/meter(V/m)
Formula of E when r is given
E=Kq/r
for isolated point charge
depends uon?
Relation of Electrical intensity:
- E is directly proportional to q(charge)
- E is inversly proportional to the square of distance.
formula
Electric intensity for dielectric
E=1/4pieE*Er q/r^2
Defination and Work
What is electric filed of lines:
The imaginanry lines drawn from Charge in electric field are called Electric field of lines or forces.
It tells the direction of electric charge force.
Direction of electric lines of forces for +ve and -ve charges.
- For +ve Field of lines are outward.———->——-
- For -ve field of lines are inward.——<———-
Electric field of lines due to 2 same charges:
While ssame charges repell eachother sso field of lines will bend opposite to one another and never overlap.
Field of lines for different charges:
while diff: charges do attract eachother so their lines of force overlap eachother and form shape.
Electric field of lienes between two oppsotie charged plates
Oppsoite charged plates attract eachother so field will over lap but will be straight from positive to negative in middle and little bend in end.
What does parallel straight equal spaced(uniform) field of lines shows
Like field oof lines btw parallel charged plates
These shows that electric intensity in same at every point.
at least 4
Properties of Electric field of lines:
- electric field of lines always move outward from positive to negative charge
- Electric field of lines never ever intersect eachother because if it could be possibe then there must be more direction for E.
- Electric field of lines are just imaginary lines for our understanding they don’t really exist.
- As distsance btw electric field of lines increase , the Electric intensity decrease.
(Φ)What is Electric Flux?
Φ is measure of number of electric fieldlines on any surface
mathamethical and Formula
Defination of Φ
number of electric field lines passing from Area. As field of lines shows represents intensity too.
* Φ=E.A
unit,quanitity and other formulas:
Φ when angle is given?
Φ=EACosQ
* Unit =Nm^2/C
* It is a dot product means scalar quantity.
on what componet Electric flux depends?
it depends upon X-component of area and Electric intensity
what is direction of area to its surface and direction of electric intensity(field lines). And direction of area to field lines?
- Area is always normal/perpendicular to surface.
- Direction of Electric field lines is perpendicular to surface.
- Area and E both are parallel to eachother
when will be value of Φ max and min?
- Φ is maximun when cos=0 means 1. this means when area and lectric intensity are in same direction
- Φ is minimun when cos=90 means 0. when area and E are perpendicular to eachother or when surface is not perpenduclar to E.
Way of finding Φ when surface is closed/sphere/circle.
when charge is enclosed into closed surface then for finding Φ we divide sphere into small patches that it may seem flat. and then find Φ for each.
what is general formula of Φ for enclosed surface
Φ=q/E*
electric flux= charge divide by epsilon not
formula for total surface area?
4 x pie x r^2
On what factor elctric flux doesn’t depend?
geometery or shape of surface.
means electric flux is not changed by changing surface design like cryst
defination and need
What is gauss’s Law?
- The net electric flux through closed surface is 1/epsilon not by net charges enclosed in closed surface.
Gauss’s law is generally needed for measuring all flux or intensity when many charges are given
Formula for gauss’s law
Φnet=qnet/E*
what is net electric charge?
Sum ofall the charges enclosed in any closed surface.
Applications of gauss’s law are?
- when many charges are enclosed in sphere /circle closed surface.
- when there are many charges on one square surface.
- when to find E between opposite charge plates.
1st step of How to find E at any point
Gaussian surface is drawn around point.
When there is charged sphere and then what is E outside the surface of sphere/
- E=K q/r^2 ..
- R radius is drawn from center of sphere to point outside sphere.
E when point is on charged sphere.
- E on surface where many charges are present is find using charge density.
- E=sigma/Epsilon not
What is charge density?
Number of charges per unit area is caleed charge density.
- it is represented by sigma.
- sigma=q/a
What is electric intensity inside hollow sphere?
- In side the hollow sphere E=0,Φ=0
- Because inside sphere there is no charge and when inside hollow sphere gaussian surface is draw it contain nothing so everything remains 0 inside sphere. no field nothing.
Formula and why?
what is Net Electric flux for infinite sheet of charges.
=sigma/2E*
sigma divided by 2 epsilon not.
Bcause due to infinite sheet of charges there are field lines ⚟ in the back and front of infinite sheet . When we sum (E.A) for two surfaces and sum them for net electric flux then we will get above value for E.
Formula and Why?
What is Electrical intensity due to oppositely charged plate?
=sigma/epsilon not
* Ressembles to electric intensity at surface of hollow sphere.
Inside the plate E=0
