What is the Maximum Power (Pmax) in a Circuit with a 220ohm Resistor (Rs)?

  • Context: Engineering 
  • Thread starter Thread starter rama1001
  • Start date Start date
  • Tags Tags
    Circuit
Click For Summary

Discussion Overview

The discussion revolves around calculating the maximum power (Pmax) for a 220-ohm resistor (Rs) in a circuit involving a Zener diode and a load resistor. Participants explore the context of the question, which is related to coursework and laboratory experiments, and discuss various factors influencing power dissipation in the circuit.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants inquire about the definition of Pmax and whether it refers to the power dissipated by the resistor Rs, suggesting that this depends on the load and other circuit components.
  • One participant mentions that their coursework involves calculating series resistance and observing stabilized output, indicating a need to analyze the circuit with and without load.
  • Another participant states that the resistor Rs must be chosen to ensure maximum power dissipation does not exceed 1.3W of the Zener diode, specifying that they selected Rs as 220 ohms with an output of 30V.
  • There are questions regarding the calculation of the voltage output from the diode bridge and the appropriateness of the chosen value for Rs, with requests for detailed calculations.
  • Concerns are raised about potential mistakes in the voltage values, particularly regarding the expected voltage across the capacitor fed by a bridge rectifier from a 24V AC source.
  • One participant expresses uncertainty about the voltage across Rs being negative, questioning the feasibility of such a scenario.
  • Another participant discusses the relationship between capacitance, voltage drop, and time, suggesting that the capacitance value could significantly affect the circuit's behavior.

Areas of Agreement / Disagreement

Participants express differing views on the calculations and assumptions regarding voltage and power dissipation in the circuit. There is no consensus on the correct approach or values, and multiple competing perspectives remain unresolved.

Contextual Notes

Participants mention various assumptions, such as the expected voltage across the Zener diode and the impact of load conditions on power calculations. There are indications of potential errors in initial calculations and the need for clarification on circuit parameters.

Who May Find This Useful

This discussion may be useful for students and practitioners involved in electronics, particularly those working on circuit design and analysis involving Zener diodes and resistive loads.

rama1001
Messages
130
Reaction score
1
Hi,
Can anyone tell me how to calculate the Pmax for Rs in the attched circuit. where Rs value is 220ohm
 

Attachments

Physics news on Phys.org
rama1001 said:
Hi,
Can anyone tell me how to calculate the Pmax for Rs in the attched circuit. where Rs value is 220ohm

What is the context of the question? Is it for schoolwork, or are you building something?

And what do you mean by Pmax? Do you mean the power that will be dissipated by the resistor Rs? That would depend on the value of the load clamp and resistor, no?
 
Hi,
i feel the same and i search throughout the web. That is my course work regarding to laborations. In that task we just calculated the series resistance and we see the stabilized output. I have to answer that question when load(R=1k /4W.) is there and without load case. i don't know how to calculate. the zener we used is BZX85/C30.
 
rama1001 said:
Hi,
i feel the same and i search throughout the web. That is my course work regarding to laborations. In that task we just calculated the series resistance and we see the stabilized output. I have to answer that question when load(R=1k /4W.) is there and without load case. i don't know how to calculate. the zener we used is BZX85/C30.

Please remember to post schoolwork questions in the Homework Help forums. I'll move this thread there now.

What is the voltage that your zener clamps at? What do you think the output DC voltage of your rectifier bridge will be, given that it has a 24Vrms input AC waveform? What will the voltage drop then be across Rs?
 
the resistor Rs must be choosen that maxium powerdessipation shoud not exceed 1.3W of the ZEner. I choosen the Rs as 220ohm and the output is 30V.
 
rama1001 said:
the resistor Rs must be choosen that maxium powerdessipation shoud not exceed 1.3W of the ZEner. I choosen the Rs as 220ohm and the output is 30V.

Ah, Rs is to limit the current that goes through the Zener diode. Okay, that makes sense.

And you are saying that the Zener diode is a 30V diode? How do you caluculate the voltage out of the diode bridge? Remember that it will not be purely DC... How did you arrive at the 220 Ohm value for Rs? Can you show us your detailed calculations?
 
total information is there in the attachment with my answer. First i made mistake in the report calculation and then again i rectified even though they are not satisfied.

could you help to dig it out.

i want remove this scrap possibly after getting the information. i don't know how to remove this entire post. Could you make a way for that.
Thanks in advance..
 

Attachments

rama1001 said:
total information is there in the attachment with my answer. First i made mistake in the report calculation and then again i rectified even though they are not satisfied.

could you help to dig it out.

i want remove this scrap possibly after getting the information. i don't know how to remove this entire post. Could you make a way for that.
Thanks in advance..

You seem to have an incorrect value for Vs. What voltage would you expect across a capacitor fed by a bridge rectifier from 24V AC? Wouldn't you expect something closer to the peak value minus the bridge drop?

The answer I get is actually a bit low even if we assume a 30V Zener, so I wonder if there could have been a mistake in the original question?

Did it not seem strange to you that the voltage across Rs appeared to be NEGATIVE? That cannot work. You must have Vs greater than Vz.
 
Of course, Vs will not be at its maximum value at all times, but it should not have dropped to anything near 24V unless C was very small, say 47uF. (IT =CV, assuming 8V drop in 10ms at 30mA gives 37.5uF.)
 

Similar threads

Engineering Diff gain of a push pull degenerated differential pair
  • · Replies 6 ·
Replies
6
Views
3K
Engineering What to Do When Input Voltage is Variable? | 5-20mA Range Explained
  • · Replies 7 ·
Replies
7
Views
3K
Engineering How Can I Use Simetrix to Verify My Amplifier Circuit Calculations?
  • · Replies 2 ·
Replies
2
Views
3K
How to find the relative error in the voltage reading
  • · Replies 9 ·
Replies
9
Views
8K
Engineering Input-referred thermal noise voltage (Razavi exercise)
  • · Replies 1 ·
Replies
1
Views
3K
Engineering Help understanding the solution to a circuit problem
  • · Replies 5 ·
Replies
5
Views
2K
Maximum combustion chamber pressure and connector rod length
  • · Replies 12 ·
Replies
12
Views
2K
Engineering Source impedance using given voltage swing and power
  • · Replies 2 ·
Replies
2
Views
2K
Engineering Why Does Vout Become Constant in a MOSFET Circuit at High Vin?
  • · Replies 1 ·
Replies
1
Views
4K
Engineering Computing the Maximum Power delivered to a Resistor
  • · Replies 7 ·
Replies
7
Views
2K