Time constant Is the time it takes for V (or I) to change by 63% of its value If C is large, more...
6
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 full charged or discharged after 3 time constants Charging : Discharging :
-
Upload
scot-thornton -
Category
Documents
-
view
213 -
download
0
Transcript of Time constant Is the time it takes for V (or I) to change by 63% of its value If C is large, more...
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
Charging:
Discharging:
LO: sketch and explain the graphs for LO: sketch and explain the 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, the movement decreases, the current flow in the circuit current flow in the circuit decreasesdecreases
LO: sketch and explain the graphs for LO: sketch and explain the 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
1) Read p243 – 246
2) Look at Example on p245
3) Do Activity 14C
Learning Tasks:
Friday, April 21, 2023
H/W booklets: Q8-14
Due: Monday 8th September
Then:
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
