Physics 8B
10 – AC Circuits
rev 4.0
1
10 – AC Circuits
1.
Consider the RC circuit shown below, powered by a 398Hz 12V r.m.s source.
30
!
10μF
12V 398Hz
a)
If the variation of current with time in the 30
!
resistor is represented by graph A
below, which of the graphs, A, B, C or D, best represents the variation with time
of:
t
i)
The potential difference across the 30
!
resistor? Explain.
ii)
The current in the 10
"
F capacitor? Explain.
iii)
The potential difference across the 10
"
F capacitor? Explain.
b)
What is the capacitive reactance of the 10
"
F capacitor?
c)
What is the total impedance of the circuit?
d)
What is the r.m.s current in the circuit?
e)
What is the r.m.s potential difference across:
i)
The 30
!
resistor?
ii)
The 10
"
F capacitor?
f)
Why do your answers in part e) not add up to the output voltage of the source of
12V?
A
B
C
D
Physics 8B
10 – AC Circuits
rev 4.0
2
2.
Consider the RL circuit shown below. Assume the inductor has a negligible
resistance. The circuit is driven by a signal generator with an output of 868Hz 2.6V
r.m.s.
22mH
50
!
2.6V 868Hz
a)
If graph A below represents the variation with time of current in the 50
!
resistor,
which one of the graphs A, B, C or D, best represents the variation with time of:
t
i)
The potential difference across the 50
!
resistor? Explain.
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 Fall '07
 SHAPIRO
 Physics, Resistance, Alternating Current, Potential difference, Inductor

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