E5C10
ELECTRICAL PRINCIPLES · Coordinate systems and phasors in electronics: rectangular coordinates; polar coordinates; phasors; logarithmic axes
E5C10E5C →
Which point on Figure E5-1 best represents the impedance of a series circuit consisting of a 400-ohm resistor and a 38-picofarad capacitor at 14 MHz?
- APoint 2
- BPoint 4
- CPoint 5
- DPoint 6
Why For a series RC circuit the impedance is Z = R - jXc, so you need the capacitive reactance. Xc = 1/(2*pi*f*C) = 1/(6.2832 x 14,000,000 x 38 x 10^-12), which works out to about 300 ohms. That gives Z = 400 - j300, plotted at 400 on the resistance (horizontal) axis and 300 units below the axis because capacitive reactance is negative. That location on the chart is point 4.
Watch out The tempting trap is the mirror-image point at 400 + j300, which is what you would get from a 400-ohm resistor in series with an inductor; capacitors always plot below the real axis.
Capacitors hang down: minus j, below the axis. Inductors point up. Get R first, then Xc = 1/(2*pi*f*C).
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
The rest of E5C
- E5C01 Which of the following represents pure capacitive reactance of 100 ohms in rectangular notation?
- E5C02 How are impedances described in polar coordinates?
- E5C03 Which of the following represents a pure inductive reactance in polar coordinates?
- E5C04 What type of Y-axis scale is most often used for graphs of circuit frequency response?
- E5C05 What kind of diagram is used to show the phase relationship between impedances at a given frequency?
- E5C06 What does the impedance 50 - j25 ohms represent?
- E5C07 Where is the impedance of a pure resistance plotted on rectangular coordinates?
- E5C08 What coordinate system is often used to display the phase angle of a circuit containing resistance, inductive…
- E5C09 When using rectangular coordinates to graph the impedance of a circuit, what do the axes represent?
- E5C10 Which point on Figure E5-1 best represents the impedance of a series circuit consisting of a 400-ohm resistor…
- E5C11 Which point in Figure E5-1 best represents the impedance of a series circuit consisting of a 300-ohm resistor…
- E5C12 Which point on Figure E5-1 best represents the impedance of a series circuit consisting of a 300-ohm resistor…