Formulas Flashcards
gauge pressure formula
Pgauge = pgd
flow speed and pressure
high flow speed has low pressure
ratio of cross sectional area to speed of liquid flow in tubes
A1V1 = A2V2
force acting on object moving underwater
Fnet = Fbuoy - mg Fbuoy = pVg mg = (p of object x V)g
how density changes speed of emerging stream
same speed for all fluid
viscosity is not in bernoulli’s equation
no term corresponding to production of heat
E = qV V = (kQ/r - kQ/r)
change in potential energy is same as energy to move charge from one place to another
work required to move charge
equal to change in potential energy
if moving from 4cm to 3cm away in a different direction, same as moving from 4cm to 3cm
when is electric field or electric potential between charges 0
electric field: halfway between charges
electric potential: never
finding electric field vs electric potential between charges
field: find hypotenuse between and multiply by E of one
charge: add both
magnitude of force charge would feel due to electric field
F=qE
if finding speed of proton and electron from same location, same q, but mass is different
a = F/m
relationship between resistance and capacitance in a network
in a network, energy consumed by resistor network is equal to energy supplied by capacitance
can measure energy consumed by resistors by using formula for capacitance
Q=CV
PE = 1/2QV
PE = 1/2CV^2
force felt between 2 charges
F = k q1q2/r^2
k
9x10^9
SI unit of charge e-
1.6x10^-19 C
electric field created by a charge
E = kQ/r^2
how charges move in conductor vs insulator
conductor: excess charge moves to opposite side of surface because they repel, no electric field is created and inside E= 0 because they cancel out
insulator: charged Q means it will become polarized
current is
Q/t
resistance changes depending on
R = pL/A
p: internal resistivity
A: area
L: length
power is
I^2R
IV
V is
IR
resistance remains constant at varying V
current reverses if V polarity reverses
resistors in series
same current
R+R
resistors in parallel
same voltage
RR/R+R
current going in + current coming out
capacitors in series
same current
CC/C+C
capacitors in parallel
same voltage
C+C
measuring current or voltage
measure current in series - for internal resistance to be negligible, you want it small
measure voltage in parallel - for internal resistance to be negligible you want it big
what a capacitor is and what they’re used for
pair of conductors that hold equal but opposite charge
creates uniform electric field throughout V=Ed
stores electrical potential energy
charge on a capacitor, how to change capacitance
Q=CV
C=EA/d
C only changes with change in area, distance, or E: permitivity of free space
how is Q=CV affected by dielectric if connected to a battery
Q increases to keep V at same level despite dielectric, increasing C
how is Q=CV affected by dielectric if not connected to a battery
becomes polarized to lower V, which then increases C
what happens to Q, C, V, electric field, and potential energy if capacitor is charged by battery, disconnected, and dielectric inserted
Q same cuz on battery C increases w dielectric so V goes down with V=Ed electric field decreases with PE=1/2QV PE also decreases where does PE go? some get stored as induced dipoles, some KE you feel when plates pull on dielectric
what happens to Q, C, V, electric field, and potential energy if capacitor is charged, and dielectric is inserted while connected
V same cuz battery
C increases, so Q increases
in V=Ed, E doesn’t change
in PE = 1/2QV, PE increases
dielectric breakdown
when electric field is so strong that dielectric becomes ionized and electrons flow
