2- Chapter 16 - Charge and Field Flashcards
What is a field
a region of space where an appropriot entity feels a force
V=
W(work)/Q(charge)
Electrostatic field strength equation. E=
Force per unit charge
F/q (or V/r for uniform field)
Q/4πε0r2
In NC-1 or Vm-1
(-dV/dr)
How is NC-1 equivelent to Vm-1?
NC-1=NmC-1/m=JC-1/m=Vm-1
Three rules for field lines
- Go from +ve to -ve
- Dont cross
- No kinks
WHat do field lines do at conductors?
meet at a right angle
A technique for drawing field lines
Use an image charge
eg if its a point charge to a planar conductor , place an image charge on the other side of the conductor.
How to work out speed of a particle from the pd.
Loss of epe=QV=1/2mv2
v=(2QV/m)0.5
Force on a wire
F=BIL
Force for a charge carrier in defelctions (a moving charge)=
F=BqV
Displacement between two plates =
VL2/4dε
Displacement angle tanθ in a electric field defection
VL/2εd
What is a velocity selector?
Electric and magnetic fields combined
they remove the differening speeds of electron from the gun by making them pass thoguh slits with a magnetic field pulling it up and a electric field down
E/B=v
Two parts of milicans oil drop experiment
- See when the drop hovers ( when mg=Eq)
- Let the drop fall at terminal velocity then mg=drag force etc.
Force between two charges=
Qq/4πε0r2
Work done =
Qq/4πε0r
Field around a point charge=
Q/4πε0r2
Potential at a point(V)=
Q/4πε0r
Define potential?
The work per unit charge done in bringign a charge from infinity to the point being considered.
What arte equpotential lines
Always at right angles to field lines
Lines where the potential is the same across that line.
Electric flux(ψ)=
ψ = EA = Q/ε0
What is electric flux
the measure of a flow of electric field through a given area.
Erest=
mc2
Principles of a linear accelerator
A series of charged electrodes
They switch between +ve and -ve at the rate an e- is being accelerated
the electrodes get longer to account for the greater speed .
What happens if something is accelerated near c.
Speed wont increase but momentum and energy will
How can accelerates be circular
ac current is used so that the pd switches at the right frequency
radius of curvature of path in a magnetic field?
r=ρ/qB
from qvB=mv2/r
momentum is approx … near c?
E/c
What part of a field distance graph shows the potential?
area under it
