unit 4 electricity

Question 1

conductor

Answer 1

material with a lot of free electrons / charge carriers

Question 2

insulator

Answer 2

material with no / very few free electrons / charge carriers

Question 3

electronic charge

Answer 3

1.6 times 10 ^-19

to measure charge use coulombmeter

Question 4

point charge

coulomb’s law

Answer 4

the electrostatic force between 2 points charges is

proportional to the product of their charges and

inversely proportional to the square of their separation

formula pg 47

Question 5

force between point charges in vacuum

formula
permittivity of free space
k value

Answer 5

pg 47

permittivity of free space = 8.85 times 10^-12 Fm^-1

Question 6

force between point charges in vacuum

formula charged particles in an insulating medium the electrostatic force between the particles decrease

Answer 6

pg 47

Question 7

coulomb’s law is used to calculate the magnitude of the electrostatic force

when apply the law only subsitute…

Answer 7

substitute magnitude only

ignore signs of charged particle

Question 8

force between point charges in vacuum

the force is a push and pull on charged particles

NOT

Answer 8

not attract and repel

Question 9

conducting charged sphere

Answer 9

pg 54

Question 10

parallel plates

uniform electric field between parallel plates

define

Answer 10

area where electrostatic force acts on charged particle.
electric field strength ( not force ) is constant at any point in the field - field lines are parallel and equally spaced

electric field directed from positive plate to negative plate

Question 11

parallel plates

work done
define
formula

Answer 11

work done is to bring a charge particle from one of the plates to another

=
change of electric potential energy

formula pg 59

Question 12

parallel plates

derived unit and base unit show work done

Answer 12

pg 59

Question 13

parallel plates

a stationary particle near negative plate will gain kinetic energy from electric potential energy and move to positive plate

formula

Answer 13

kinetic energy = electric potential energy

pg 60

Question 14

parallel plates

particle starts from rest at middle of parallel of the plates

formula

Answer 14

kinetic energy = electric potential energy

formula

Question 15

thermionic emission

not all electrons in electron beam with the same kinetic energy

why

Answer 15

because of different initial speed when electron leave cathode

electrons gain thermal energy to overcome the electrostatic force and release from metal surface

Question 16

thermionic emission

equipotential surface

define

Answer 16

surface where all the point on it with same potential

between parallel plates, any point equal distance from the plates has the same potential

Question 17

graphs

separation between plates
potential difference across plates
distance from ground plate

Answer 17

pg 61

Question 18

stationary oil drop

oil drops charged by………

Answer 18

oil drops charged by friction when pass through nozzle

when oil drops pass through the parallel plates,
oil drops act by weight and electric force. ignore air resistance

weight considered because as weight is comparable to electrostatic force

if weight and electrostatic force in the same direction , oil drop accelerate down

Question 19

pg 62

Answer 19

pg 62