22. electric fields

Question 1

what is a field

Answer 1

a field is a region in the universe where an object placed inside of it can experience a non-contact force due to its position in the field

Question 2

how to draw electric field lines for an object

Answer 2

• straight lines
• arrow pointing towards object

shows the path that a positively charged particle would take if it were placed at this point

Question 3

what type of particle will experience an electric force inside the electric field

Answer 3

a charged particle

Question 4

what is an electric field

Answer 4

a region around a charged particle within which a non contact force would be exerted on other charged particles

Question 5

difference between radial and uniform fields

Answer 5

radial fields can be formed around any particle
uniform field is formed by parallel metal plates (such as a capacitor)

Question 6

what are 2 differences between grav and elec fields?

Answer 6

1. field strength of each field represented with different constants
2. electric can be attractive or repulsive, gravitational can only be attractive

Question 7

state coulombs law

Answer 7

1. the force in directly proportional to the produce of their charges F=Qq
2. the force is inversley proportional to the square of the distance (r) between them F=1/r^2

the constant of proportionality is 1/ (4 pi ε0) where ε0 = 8.85x10^-12

Question 8

what are the 3 assuptions for coulomb’s law?

Answer 8

1. objects are considered point charges
2. the charges objects are not touching
3. the charged objects must be stationary

Question 9

what is electric field strength

Answer 9

the force per unit positive charge experienced at a position in a field

Question 10

what is the equation for electrical field strength

Answer 10

electric field strength = force / charge
E = F / Q

Question 11

what is an equation for electric field strength (2)

FOR UNIFORM ELECTRIC FIELDS ONLY

Answer 11

electric field strength = potential difference / distance
E = V / d

FOR UNIFORM ELECTRIC FIELDS ONLY
FOR UNIFORM ELECTRIC FIELDS ONLY

Question 12

what is the equation for electric field strength (3)

FOR RADIAL ELECTRIC FIELDS ONLY

Answer 12

E = Q / 4 pi ε0
as E=F/Q
F=EQ
and the Qs cancel

FOR RADIAL ELECTRIC FIELDS ONLY

Question 13

if a POSITIVELY charged particle is moving into a uniform electric field, with the -ve plate on top and +ve plate on bottom, which way will it go

Answer 13

PARABOLIC PATH towards -vely charged plate (upwards ish)

still going forwards due to inertia

Question 14

if a NEGATIVELY charged particle is moving into a uniform electric field, with the -ve plate on top and +ve plate on bottom, which way will it go

Answer 14

PARABOLIC PATH towards +vely charged plate (downwards ish)

still going forwards due to inertia

Question 15

what is electric potential

Answer 15

the word done per unit positive charge to move a charged object from infinity to that point in the electric field

Question 16

at what distance from the charged object is the electric potential zero

Answer 16

infinity

Question 17

what is the equation for electrical potential?

with electric potential energy

Answer 17

electric potential = electric potential energy / charge

V = Ep / Q

units: JC^-1 = 1Volt

Question 18

what is the equation for electrical potential? and what is its limitation

in booklet

Answer 18

V = Q / 4πε₀r

limitation: only applicable to radial fields

Question 19

what is electric potential energy

Answer 19

the word done in moving a charged object from infinity to that point in the electic field

NO PER UNIT CHARGE

Question 20

define potential difference

Answer 20

the difference between two potential areas, which the charged object has moved between

Question 21

can charged move without work being done

Answer 21

YES!
a charged object can move along lines of equipotential without work being done
HOWEVER: it cannot move between difference potential levels

Question 22

how to find equipotential lines form an electrical field diagram

Answer 22

• represented by dashed lines
• at 90deg to electric field lines
• circular for radial field
• straight for uniform field