Physics 122 - Lecture
Date: 3/23/16
Questions?
Announcements/Reminders
MP HW #08 – Due TODAY, by 11:59 pm.
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Written HW #08 – Due NOW.
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MP HW #09 – Due WEDNESDAY, 3/30, by 11:59 pm.
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Written HW #09 – Due WEDNESDAY, 3/30.
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Reading assignment (check website) – Due on 3/28/16.
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EXAM 2 – April 1
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Last Class…
Clicker question
What must be done to a capacitor in order to increase the
amount of charge it can hold (for a constant voltage)?
A) increase the area of the plates
B) decrease separation between the plates
C) decrease the area of the plates
D) either (A) or (B)
E) either (B) or (C)
+Q
–Q
Clicker question
What must be done to a capacitor in order to increase the
amount of charge it can hold (for a constant voltage)?
A) increase the area of the plates
B) decrease separation between the plates
C) decrease the area of the plates
D) either (A) or (B)
E) either (B) or (C)
+Q
–Q
Dielectrics
Clicker question
How does the charge Q1 on the first capacitor (C1) compare
to the charge Q2 on the second capacitor (C2)?
1) Q1 = Q2
C2 = 1.0  F
2) Q1 > Q2
3) Q1 < Q2
4) all charges are zero
10 V
C1 = 1.0  F
C3 = 1.0  F
Clicker question
How does the charge Q1 on the first capacitor (C1) compare
to the charge Q2 on the second capacitor (C2)?
1) Q1 = Q2
C2 = 1.0  F
2) Q1 > Q2
3) Q1 < Q2
4) all charges are zero
10 V
C1 = 1.0  F
C3 = 1.0  F
Example:
Two identical capacitors are connected in parallel and each acquires a
charge Qo when connected to a source of voltage Vo. The voltage source
is disconnected and then a dielectric (K = 3.2) is inserted to fill the
space between the plates of one of the capacitors. Assume that the
capacitor without the dielectric is the first and the capacitor with the
dielectric is the second.