Radial Electric Fields Flashcards
what do the field lines of a positively charged particle look like
- the lines are drawn perpendicular to the surface of the particle
- they would all be equidistant from each other
- with arrows pointing outwards
what does the distance between the field lines represent
the strength (potential) of the field
how do the field lines accurately represent the field strength of a particle
- the further you get away from the particle, the further the lines get from each other
- which correctly indicates a decrease in the field strength the further you get from the particle
what does a decrease in field strength mean about the change in potential
the potential would change less quickly
what do the field lines of a negatively charged particle look like
- the lines are drawn perpendicular to the surface of the particle
- they would all be equidistant from each other
- with arrows pointing inwards
why do we know there is no electric field within a charged sphere
because the charged particle feels no resultant force when on its own
why is there no resultant force within the sphere
the overall effect of the all the charges and their directions cancel out
where should you start distance measurements on the sphere when carrying out calculations
from the centre
what type of fields do spherical objects create
radial fields
what is the equation for calculating the radial field strength at a distance r from a charge Q
E = Q / 4 pi e(0) r^2
what is the constant e(o), which is actually the fancy sigma (backwards 3)
- the permittivity of space
- e(0) = 8.85x10-12 Fm-1
why does this equation technically only apply to fields produced in a vacuum
- because of the constant e(0)
- it relates to the ability of the fabric of the universe to support electric fields
- but air is considered to be close enough
how would we account for more extreme media like an electric field being produced in water
- we would use the relative permittivity of that medium
- given the symbol e(r)
what does electric field strength tell us (relating back to potential)
how quickly the electric potential is changing
what would a stronger field therefore have
equipotentials closer together
what would you write an equation showing the electric field strength is equal to the rate of change of potential (V) with respects to the distance (x)
E = -dV / dx
what is the equation for radial field potential at a distance r from a charge Q
V = Q / 4 pi e(0) r
how would you calculate the electric potential at a distance of 1 angstrom (1x10-10 m) from a proton
- using the V = equation
- Q would be the charge of a proton
- which is equal to the charge of an electron
- so Q = 1.6x10-19, then you would just input the other values
what kind of shape is most ideal for concentrating charge at one point
spikes
why are spikes / pointed shapes ideal
- because they would have close field lines due to their low surface ares
- so the field around them would be strong
how to lightning conductors shaped like this protect buildings
- the concentrated charge on the conductors attract opposite charges more strongly
- so lightning is more likely to hit them than the building
- the field can even be strong enough to cause a charge leakage through the conductor
- if this happens before charge builds up to the point of a lightning strike
- the chances of having one is reduced which further protects the building
what would the field lines of a proton being attracted to an electron look like
- the lines would connect at the centre
- still being perpendicular to the surface of both particles
- the centre line would therefore be straight while the others would be curved
- the arrows would be pointing from the +ve to -ve
- with both particles having arrows pointed towards and into them from the back, still perpendicular
what would the field lines of a proton being repelled by another proton look like
- all lines would be perpendicular from the surface
- but the lines would curve upwards or downwards to avoid each other
- the arrows would still be pointing outwards (as well as the lines at the back)
what would the field lines of an electron being attracted to a positive sheet look like
- the field lines would connect them, still being perpendicular to both surfaces
- the lines at the back would be feeding into the electron
- with all arrows pointing towards the electron