Upload
lewis-sims
View
220
Download
1
Tags:
Embed Size (px)
Citation preview
Do now: NCEA 2006
1) Calculate the total capacitance
2) Calculate the total charge
stored in the capacitors
3) Calculate the total energy
stored in the capacitors
4) Calculate the voltage across the 4.00 μF capacitor
Friday, April 21, 2023
QVE 21
Q CV 21 CCCT
21
111
CCCT
Sketch and explain these graphs for Sketch and explain these graphs for chargingcharging a capacitor a capacitor
It’s easy at first because the It’s easy at first because the plates are empty, but as plates are empty, but as they fill the stored charge they fill the stored charge starts to repel further charge starts to repel further charge and the rate decreasesand the rate decreases
Voltage across capacitor
t
Vmax
Current in circuit
t
Imax
As the rate of charge As the rate of charge movement decreases, movement decreases, the current flow in the the current flow in the circuit decreasescircuit decreases
Sketch and explain these graphs for Sketch and explain these graphs for dischargingdischarging a capacitor a capacitor
The voltage will be at a max to The voltage will be at a max to begin with, drops quickly at first begin with, drops quickly at first (due to maximum repulsion), but (due to maximum repulsion), but then more slowly as fewer then more slowly as fewer charges remain on the capacitor.charges remain on the capacitor.
The current will be large The current will be large at first, but decrease as at first, but decrease as potential left to “push” potential left to “push” decreasesdecreases
Voltage across capacitor
t
Vmax
Current in circuit
t
Imax
Time constant
Is the time it takes for V (or I)
to change by 63% of its value
If C is large, more charge can be stored, so takes longer to fill/empty.
More R in the circuit means smaller current, so longer to fill/empty.
RC
A cap is considered fully
charged or discharged
after 3 time constants
Skim read p229 – 233
Look at Example on p231
*** Do Activity 14C ***