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3) modify the schematic below to change the polarity of the out voltage…

Question

  1. modify the schematic below to change the polarity of the out voltage created by the circuit in figure 2.
  2. draw the waveform found across the resistor for the circuit in figure 3. source is 120 v rms @ 240 hz. determine the correct output voltage level.

Explanation:

Question 3
Brief Explanations
  • Diodes allow current flow in one direction (from anode to cathode). Reversing the diode’s orientation reverses the direction of current through the load (resistor), thus reversing the output voltage’s polarity.
  • In a rectifier circuit, the diode’s direction determines the polarity of the rectified output. Swapping its anode - cathode connections flips the output voltage’s positive and negative terminals relative to ground.
Question 4

Step 1: Determine the type of rectifier

The circuit in Figure 3 is a full - wave bridge rectifier (four diodes in a bridge configuration), so it produces a full - wave rectified output.

Step 2: Calculate the peak input voltage

Use the formula \(V_p = V_{rms}\times\sqrt{2}\). Given \(V_{rms}=120\space V\), we calculate \(V_p = 120\times\sqrt{2}\approx169.7\space V\).

Step 3: Relate input peak voltage to output voltage

In a full - wave bridge rectifier, the output voltage across the resistor (without a filter capacitor) has a peak value equal to the peak value of the input voltage (since the diodes in the bridge rectifier re - direct both half - cycles of the AC input to the load in the same direction). So the output voltage level (peak) is approximately \(169.7\space V\). If we consider the average (DC) value, we use the formula for the average of a full - wave rectified signal \(V_{avg}=\frac{2V_p}{\pi}\), which gives \(V_{avg}\approx108\space V\), but the peak value is a more direct measure of the voltage across the resistor in the unfiltered case.

Answer:

To change the polarity of the output voltage, reverse the direction of the diode (or the diodes, if multiple) in the circuit. For the given schematic (Figure 2, which appears to be a rectifier circuit with a diode and a zener diode), flipping the main rectifier diode (the one before the zener) will invert the output voltage polarity. The modified schematic will have the diode's anode and cathode swapped, so the current flows in the opposite direction, reversing the output voltage's polarity.