chapter 9 Flashcards
công thức emf
total workdone when charge goes round a complete circuit
Potential difference
used when charges lose energy
energy given up by unit charge as it move from point A to point B
pd formula
p.d = emf - I x r
electric field
E=F/Q
E=V/d
In series
I1=I2=I
R1 + R2 = Rt
V1 + V2 = Vt
In parallel
I = I1 + I2 V = V1 = V2 1/R = 1/R1 + 1/R2
Resistivity
p= R x (cross sectional area / length)
Energy in điện
E= V x Q
Power
P= VI = IIR = V^2/R
energy transferred
E = VIt
Kirchoff’s first law
sum of the current entering any point in a circuit is equal to the sum of the currents leaving that point
ohm’s law
the current through a conductor between two points is directly proportional to the potential difference across the two points.
A non- ohmic device
doesn’t follow Ohm’s Law.
Semi Conductor Devices
their current is not proportional to the voltage linearly,
ohmic device
current varies proportionally to voltage
thresh hold voltage
0.6 v
bulb/filament lamp
as V increase => more electron => more collision with fillament particles => particle move around more => gain Electron and heat up => more resistance
as temp increase so does the réistance
potential divider equation
Vout = (R2/R1+R2) x Vin
electric field
- EF is the same at all point
- Force is the same at all point
- Constant force => constant acceleration
- the closer the plates => higher voltage => electric field strength and vice versa
- An electric charge moving through a uniform electric field follows a parabolic path
