Is the Resistance of a Diode Higher in D.C. or A.C.?

In summary, the slope of DC resistance is lower than the slope of AC resistance, so DC resistance is always more than AC resistance.
  • #1
Pushoam
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51

Homework Statement


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Homework Equations

The Attempt at a Solution


Considering I- V characteristics graph, the slope for D.C. resistance is lower than that of the A.C. resistance. Now, the resistance is inverse of the corresponding slope. So, D.C. resistance should be more than A.C. resistance.
 
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  • #2
Pushoam said:

Homework Statement


View attachment 211098

Homework Equations

The Attempt at a Solution


Considering I- V characteristics graph, the slope for D.C. resistance is lower than that of the A.C. resistance. Now, the resistance is inverse of the corresponding slope. So, D.C. resistance should be more than A.C. resistance.
Can you show us on the I-V curve? I think I know what the answer is, but I'm not sure.
 
  • #3
berkeman said:
Can you show us on the I-V curve? I think I know what the answer is, but I'm not sure.
upload_2017-9-14_22-5-59.png

It is clear that the slope for D.C. is lower than that for A.C.
Hence, the resistance for the D.C.is greater than that for A.C.
Right?
 

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  • #4
Pushoam said:
Hence, the resistance for the D.C.is greater than that for A.C.
Yes, correct. With that graph you can show that the tangent to the graph always has a greater slope than the line from the origin to the point on the graph (at least in the 1st quadrant).

Quiz Question -- is it still true in the 3rd quadrant for reverse bias? Include low-level reverse bias and as the diode starts to go into reverse breakdown... :smile:
 
  • #5
berkeman said:
Quiz Question -- is it still true in the 3rd quadrant for reverse bias? Include low-level reverse bias and as the diode starts to go into reverse breakdown... :smile:
Before the breakdown voltage, the DC resistance is less than AC resistance.
After the breakdown voltage, the DC resistance is more than the AC resistance.
 
  • #6
Is the definition of linear device following?
Those devices who follow the rule V = IR, are known as linear devices.
 
  • #7
Pushoam said:
Before the breakdown voltage, the DC resistance is less than AC resistance.
Can you show on the I-V curve why you think this is true? :smile:
 
  • #8
berkeman said:
Can you show on the I-V curve why you think this is true? :smile:
upload_2017-9-14_23-2-40.png

Sorry, even before breakdown, the slope of AC is more than that of DC.
So, AC resistance is smaller than the DC resistance.

So, DC resistance is always more than the AC resistance. Right?
 
  • #9
Pushoam said:
So, DC resistance is always more than the AC resistance. Right?
Yep! Good job. Looking at the slope really helps on this type of question. You can also show it mathematically by taking the first derivative of the Diode Equation, but this one is pretty easy to see graphically. :smile:
 
  • #10
:smile::smile::smile::smile:
Done!
Thank you, thanks a lot for guiding me.
 

1. What is the resistance of a diode?

The resistance of a diode varies depending on the type of diode and its operating conditions. Generally, it can range from a few ohms to several megaohms.

2. How does the resistance of a diode affect its function?

The resistance of a diode is an important factor in its function. It determines the amount of current that can flow through the diode and can influence its ability to rectify and amplify electrical signals.

3. How is the resistance of a diode calculated?

The resistance of a diode can be calculated using Ohm's Law, which states that resistance (R) is equal to the voltage (V) divided by the current (I). In the case of a diode, the voltage and current are not constant and may vary depending on the applied voltage and the diode's characteristics.

4. What factors can affect the resistance of a diode?

The resistance of a diode can be affected by several factors, including temperature, forward and reverse bias, and the material and construction of the diode. Additionally, the resistance may change over time due to aging or damage to the diode.

5. How can the resistance of a diode be measured?

The resistance of a diode can be measured using a multimeter or an ohmmeter. To measure the resistance, the diode must be disconnected from any circuit and the multimeter's probes must be placed on the diode's terminals. The measured resistance value will depend on the type of measurement (forward or reverse bias) and the operating conditions of the diode.

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