Electric Charges and Fields

Question 1

What is smallest unit of charge?

Answer 1

Stat coulomb also called franklin or esu (electrostatic unit)
1 coulomb = 3 multiply 10*9 stat coulomb

Question 2

Largest unit of charge

Answer 2

Faraday
1 F = 96500 C

Question 3

Proton, mass and charge

Answer 3

Mass = 1.67 • 10-27 kg
Charge = +1.6 • 10-19 C

Question 4

Electron, mass and charge

Answer 4

Mass= 9.1 • 10-31 kg
Charge= 1.6 • 10-19C

Question 5

Neutron, mass and charge

Answer 5

Mass= 1.67 •10*-27 kg
Charge=0

Question 6

Is charge variant or invariant?

Answer 6

Charge, unlike mass is invariant, which means it does not change with time

m= m not / root 1- (v sq/c sq)

Question 7

1 coulomb has charge of how many electrons

Answer 7

6.25 • 10^18 e = 1 C

Question 8

Alpha particle, charge and mass

Answer 8

Charge = +2e
Mass = 4 p

Question 9

Charge on deutron

Answer 9

+e ( because of one proton and removal of one electron)
Remove one electron to from deuterium to get deutron

Question 10

Is positive ions conserved in nature?

Answer 10

No, total charge is

Question 11

Formula for specific charge and SI uni

Answer 11

S = charge/mass or C/kg

Question 12

Method of charging for insulators

Answer 12

Rubbing/friction
Glass rod (+) and silk (-)
Fur (+) and ebonite rod/rubber( -)

Question 13

What is a sure test of electrification and magnetism?

Answer 13

Repulsion (can only happen when both charged)

Attraction can happen also if a body is neutral by induction

Question 14

What is gold leaf electroscope used for?

Answer 14

Device to roughly estimate charge on body

Question 15

What is Coulomb’s law and constant

Answer 15

F = k q1 q2/ r^2

k = 9 • 10^9 Nm^2/C^2

Question 16

Which is stronger, electrostatic or gravitational force?

Answer 16

Electro, as gravitation is the weakest

Question 17

1 Newton has how many dyne

Answer 17

10^5 dyne = 1 N

Question 18

Formula, SI unit, value of permitivity

Answer 18

€not= 8.85 × 10⁻¹² F/m
Farad/m or C^2/Newton m^2

F= qq/4 pi €not r^2

Question 19

Formula of dielectric constant and formula of force with it

Answer 19

Also denoted by k but different from coulomb constant
k = €/€not
medium/free space

Question 20

Dielectric constant is infinity for and what does that mean for force

Answer 20

Conductors
F’=0 because F’ = F/K = F/infinity = 0

Question 21

Where is null point for 2 like or similar charges and formula for this

Answer 21

Null point in between where its distance from smaller charge is x

x = r / (root n) +1

where r is distance between the 2 charges
And n= bada charge/ chhota charge

Question 22

Where is null point for opposite charges and formula for it’s distance

Answer 22

Null point is to the side of both charges, not in between, with x distance from smaller charge

x = r/ (root n) - 1

Where r is the distance between 2 charges
And n is ration of big charge by smaller charge

Question 23

2 vectors A and B at an angles, formula for resultant

Answer 23

R = underoot A^2 + B^2 + 2AB cos theta

If A=B then R= 2A cos (theta/2)

Question 24

Resultant when A and A have 60 degree

Answer 24

(Root 3) A

Question 25

Resultant when A and A have 90 degree

Answer 25

(Root 2) A

Question 26

Resultant when A and A have 120 degree

Answer 26

R = A

Question 27

Coulomb’s law in vector form

Answer 27

F cap = k q1 q2 (r vector/arrow) /r^3 As r vector= r • r cap

Question 28

In 2 charges on pendulum repelling, the ratio of their tan theta is what

Answer 28

Tan theta 1/ tan theta 2 = m2/ m1 This is independent of charge

Question 29

Formula for electric field strength/ electric field intensity. Definition and SI unit

Answer 29

F= kq/ r^2 Force experienced per unit POSITIVE test charge SI is N/C or another unit V/m

Question 30

Electric field due to circular arc

Answer 30

(2k lamda/r ) sin (alpha/2)

Question 31

Electric field due to semi circular arc and infinite charged rod in x direction

Answer 31

2k lamda/r O for charged rod in y direction

Question 32

Electric field due to ring at an axis

Answer 32

kQx/ (x^2 + R^2) ^3/2 Where E max is at x = +- R/ root2

Question 33

Electric field due to charged rod

Answer 33

E in x = k lamda/ r (sin alpha + sin beta) E in y = k lamda / r (cos alpha - cos beta)

Question 33

Electric field at axial point of rod with L length at a distance x

Answer 33

E = kQ/ r (r+L)

Question 34

Force experienced by negative charge in electric field

Answer 34

F = -qE (F and E vector)

Question 35

What are the equations of motion valid for motion of charged particle in electron field

Answer 35

v = u + at s = ut + (1/2) at^2 v^2 = u^2 + 2as s = [(u+v)/ 2] • t

Question 36

Which of the following can’t be deflected by electric field? 1. X-ray 2. B particles 3. Proton 4. Alpha particles 5. Gamma rays 6. Neutron

Answer 36

X-ray, gamma ray and netron because they don’t have any charge Beta have -1 charge

Question 37

Electric dipole formula for p

Answer 37

p = qd Coulomb metre p and d are vectors

Question 38

Electric field due to dipole at axial point, equatorial point, general point

Answer 38

2kp/r^3 -kp/ r^3 kp/r^3 • underoot 1+ 3 cos sq theta

Question 39

Formula for torque on dipole in electric field

Answer 39

p E sin theta Min for 0degree and 180 degree Max for 90degree with torque=pE

Question 40

Dipole oscillation formula for time period

Answer 40

T = 2 pi underoot I/ pE T= 2pi/ omega Omega = underoot pE/I

Question 41

Electric flux formula

Answer 41

Fi = E A cos theta Where A or area vector is perpendicular to surface

Question 42

Gaus law formula

Answer 42

Integral of E • ds = fi = q enclosed/ €not

Question 43

According to gaus law electric field in, on and out hollow sphere and solid sphere (non conducting)

Answer 43

Hollow or solid conducting sphere E in = 0 E out = kQ/r^2 E on = kQ/R^2 = sigma/ €not Solid non-conducting E in = kQr/R^3 E out = kQ/r^2 E on = kQ/R^2

Question 44

Electric field of infinite line or charge

Answer 44

E = 2k lamda/ r

Question 45

Electric field of infinite non conducting sheet (cylindrical or cuboidal

Answer 45

E = sigma/ 2 € not It is independent of r

Question 46

Flux through a cube with charge at the centre, face centre, edge centre and corner

Answer 46

Flux when centre of cube = q/ € not (Through each face q/ 6 € not) Face centre = q/2 € not Edge = q/ 4 € not Corner = q/ 8 € not