Electric Fields Flashcards
What is Coulomb’s Law in words?
The force between two positive charges is
Proportional to the product of their charge
Inversely proportional to the square of their distance apart
What is the equation for Coulomb’s Law?
F=1/(4πε) Qq/r²
What is 1/(4πε)?
Electric Field constant/multiplier
ε is the Permittivity of free space (8.98x10^9)
What is an Electric Field?
The force acting on a unit positive charge
What are the units of an Electric Field?
Newtons per Coulomb (NC^-1)
or
Volts per Meter (Vm^-1)
What equation is the defintion of an Electric Field?
E=F/Q
What equation is used to calculate the strength of an Electric Field at a point?
E=1/(4πε) Q/r²
Where is the Electric Field strongest on a sphere?
On the surface
What is the Electric Field inside a sphere?
Zero
Is an Electric Field a scalar or vector?
Vector
Which way do Electric Field lines point?
Away form positve
Towards Negative
What does the magnitude of the Electric Field depend on?
The charge creating the field
What is E proportional to?
Q
What is E inversely proportional to?
r²
What are the units of Electric Potential Energy?
Joules (J)
What is the definition of Electric Potential Energy?
The work done in moving a charge from infinity to a distance (r) within the Electric Field
What is the equation for calculating Electric Potential Energy?
W=1/(4πε) Qq/r
not on data sheet
What is W proportional to?
What is W inversely proportional to ?
r
What is the equation for calculating the change in Electric Potential Energy?
ΔW=Qq/(4πε) (1/r(2) - 1/r(1))
What are the units for Electric Potentials?
Joules per Coulomb (JC^-1)
or
Volts (V)
What is the definition of Electric Potentials?
The work done in moving a unit positive charge from infinity to a distance r within an Electric Field
What is the definition of Electric Potentials as an equation?
V=W/Q
What is the equation for calculating Electric Potentials?
V=1/(4πε) Q/r
(As Electric Potentials is the same as Electric potential energys but for a unit positve charge, imagine
1/(4πε) Qq/r with q=1 as q is a unit positive charge)
Are Electric Potential Energies positive or Negative?
They are both Q q W \+ - = - \+ + = + - - =+
Are Electric Potentials positive or negative?
They can be either
A positive charge produces a positve potential
A negative charge produces a negative potential
What is an Equipotential?
Lines joining points of equal potential
They are always perpendicular to field lines
What is the Electric potenial within a sphere?
The same as the surface as energy has been used to move the coulomb to the surface therefore to conserve energy it must be the same as no additional work is doen within the sphere
Where is the greatest Electric Potential on a sphere?
On the surface
What is the gradient on a potential-distance graph?
The Field strength at that radius
What equation links Electric Fields, Potential Difference and Distance?
E=-ΔV/Δr
What is a Uniform Electric Field?
A field btween two metal plates with a p.d across them\
What equation is used to calulate the strength of a Uniform Electric Field?
E=V/d
How do you calculate the acceleration due to a Uniform Electric Field?
a=VQ/dm
What is the total charge of an Uniform Electric Field?
0
How is motion in a Uniform Electric Field modeled?
projectile motion
What type of current is present in a the shuttle ball experiment?
DC
As the ball transfers a small amount of charge from plate to plate.
