Redrawing Circuits for Diode Analysis: Is It Valid?

In summary, the circuit has voltmeters with negligible conductance, a cell with negligible internal resistance, a conducting diode, and resistors. To determine the current through the diode, the circuit can be redrawn with the voltmeters in parallel with lower resistance elements. As long as the diode is ideal, the current under reverse bias is zero, making the approximation accurate.
  • #1
QueenFisher
in the diagram below, the voltmeters are as near to perfect as possible, the cell has negligible internal resistance. the red blob is a conducting diode, and the green blob is non-conducting. the coloured boxes are resistors. in order to work out the current through the red diode, is it ok to redraw the circuit as shown on the left? i figured that as the voltmeters have very high resistance, there'd be virtually no current through them, and none at all through the green diode. is this an ok way of looking at it?

http://home.ripway.com/2005-7/361234/circuit.bmp
 
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  • #2
Negligible Conductances

I think you are on the right track. The conductance of Voltmeters can be neglected if they are in parallel with a much lower resistance element. Likewise, the current through the "non-conducting" diode can be neglected if it is much less than that through the reddish rectangle. If it is an ideal diode, then the current under reverse bias is zero, and your approximation is exact.
 
  • #3
yes my teacher told me to take the resistance of the reverse-biased diode as zero, so i hope it will work.

thanks for checking it!
 
  • #4
I think you are all set, but didn't your teacher mean that the current of the reverse biased ("non-conducting") diode is zero, or the conductance of the reverse biased diode is zero, or the resistance of the reverse biased diode is infinite?

Best Regards,
Walter
 
  • #5
sorry 'bout that, i typed it wrong. :blushing: thanks for noticing.
 
  • #6
Don't mention it -- I thought it was a typo, but wanted to make sure.
 

1. What is a diode?

A diode is a two-terminal electronic component that allows current to flow in only one direction. It acts as a one-way valve for electric current, allowing it to flow from the anode (positive terminal) to the cathode (negative terminal) but not in the reverse direction.

2. How does a diode work?

A diode is made up of a p-type semiconductor material (with positively charged holes) and an n-type semiconductor material (with negatively charged electrons). When a voltage is applied in the forward direction, the p-type material becomes positively charged and the n-type material becomes negatively charged, allowing current to flow through the diode. When a voltage is applied in the reverse direction, the diode becomes non-conductive and does not allow current to flow.

3. What is a circuit?

A circuit is a complete path that allows electric current to flow from one point to another. It is made up of various components, such as resistors, capacitors, and diodes, connected by conductive wires. Circuits can be either open (broken) or closed (complete) depending on the presence of a continuous path for current to flow.

4. How do diodes affect circuits?

Diodes are commonly used in circuits to control the flow of current and to prevent damage to other components. They can also be used to convert alternating current (AC) to direct current (DC) by allowing current to flow in only one direction. Additionally, diodes can be used as voltage regulators, limiting the voltage across a circuit by allowing current to flow only when the voltage reaches a certain threshold.

5. What are some common problems with diodes and circuits?

Some common problems with diodes and circuits include short circuits, open circuits, and reverse polarity. Short circuits occur when two or more points in a circuit with different voltages are connected, causing a large flow of current and potentially damaging components. Open circuits occur when a break in the circuit prevents current from flowing. Reverse polarity can occur when a diode is connected in the wrong direction, causing the circuit to malfunction or not work at all.

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