Two basic diode and capacitor circuits

[Noob of the Maths]

Homework Statement

Circuit 1. Calculates the source voltage, diode and resistance. Plot an I - V curve of the diode and interpret.

Circuit 2. Peak voltages or amplitude taking into account the oscilloscope's v / div scale. Measure the voltage ripple across the load and measure the period, T, taking into account the ms / div scale and thereby calculate the frequency, f of the source voltage.

Relevant Equations

Ohm`s law

Hi there!
I have resolve this basic circuit, but, i have a little questions about.

The first circuit its:

The diode in all voltaje cases act like a switch, so, the courrent of all components and voltage of the resistance its zero. I graph the curve according my interpretation. My question its about if my interpretation its correct.

The second circuit its:

My question its about the values. I obtain it just counter the squares, like the right image.

Thanks 4 read :)

 

[Steve4Physics]

Homework Statement:: Circuit 1. Calculates the source voltage, diode and resistance. Plot an I - V curve of the diode and interpret.

Circuit 2. Peak voltages or amplitude taking into account the oscilloscope's v / div scale. Measure the voltage ripple across the load and measure the period, T, taking into account the ms / div scale and thereby calculate the frequency, f of the source voltage.
Relevant Equations:: Ohm`s law

Hi there!
I have resolve this basic circuit, but, i have a little questions about.

The first circuit its:
View attachment 288583
The diode in all voltaje cases act like a switch, so, the courrent of all components and voltage of the resistance its zero. I graph the curve according my interpretation. My question its about if my interpretation its correct.

The second circuit its:
View attachment 288584View attachment 288585
View attachment 288586

My question its about the values. I obtain it just counter the squares, like the right image.

Thanks 4 read :)

Hi @Noob of the Maths. Welcome to PF.

I find it difficult to understand the questions and your answers. Maybe partly because they have been incompletely/incorrectly translated from another language (Spanish?).

Here is a list of some of the problems
_____________
Q1.

It is impossible to calculate the resistance of R2. There isn’t enough information (current and voltage needed).

Your graph is badly drawn because the voltages you marked on the V-axis are at completely incorrect positions. Also, it is usual to show reverse voltages as negative values.

Are you sure the question is accurate and complete?
_________
Q2.

In your picture, part of the circuit is covered by the oscilloscope. I guess this may include a diode. The complete circuit is needed.

It is not clear which voltage in the circuit is being measured by the oscilloscope.

I don’t know what the column-heading ‘Charge ‘ means.

You have calculated frequency incorrectly because the period is in milliseconds, not seconds.

You have not given any resistor values. A current can’t be calculated from voltage unless the resistance (or power) is known.

The symbol for milliamp is mA, not Ma.

Are you sure you have the question correct and complete?
_________

There are too many gaps/mistakes, making it impossible to help you. Consider improving the questions if no one else can help.

 

[Noob of the Maths]

Hi @Noob of the Maths. Welcome to PF.

I find it difficult to understand the questions and your answers. Maybe partly because they have been incompletely/incorrectly translated from another language (Spanish?).

Here is a list of some of the problems
_____________
Q1.

It is impossible to calculate the resistance of R2. There isn’t enough information (current and voltage needed).

Your graph is badly drawn because the voltages you marked on the V-axis are at completely incorrect positions. Also, it is usual to show reverse voltages as negative values.

Are you sure the question is accurate and complete?
_________
Q2.

In your picture, part of the circuit is covered by the oscilloscope. I guess this may include a diode. The complete circuit is needed.

It is not clear which voltage in the circuit is being measured by the oscilloscope.

I don’t know what the column-heading ‘Charge ‘ means.

You have calculated frequency incorrectly because the period is in milliseconds, not seconds.

You have not given any resistor values. A current can’t be calculated from voltage unless the resistance (or power) is known.

The symbol for milliamp is mA, not Ma.

Are you sure you have the question correct and complete?
_________

There are too many gaps/mistakes, making it impossible to help you. Consider improving the questions if no one else can help.

Thanks for reply!
In the first question is to obtain the values of the table by varying the source voltage.
Since the diode is reverse biased, the current voltage would always be zero, as would the diode current.
For that reason, I set such values to zero in the table.

For the I - V curve of the diode, I used the curve of the silicon diode and put the voltage I used, implying that the current will always be zero until the voltage reaches 50V.

Q2

This is the circuit, the values are obtained from the table using the oscilloscope.
For this I used the count of frames on which the waves appear.

 

[Steve4Physics]

Thanks for reply!
In the first question is to obtain the values of the table by varying the source voltage.
Since the diode is reverse biased, the current voltage would always be zero, as would the diode current.
For that reason, I set such values to zero in the table.

For the I - V curve of the diode, I used the curve of the silicon diode and put the voltage I used, implying that the current will always be zero until the voltage reaches 50V.

Q2
View attachment 288616
This is the circuit, the values are obtained from the table using the oscilloscope.
For this I used the count of frames on which the waves appear.

It sounds like you are doing circuit-simulations using a software teaching package.

Please answer the question shown below in bold:

A. Are the circuits given to you? Can you change them?
___________________

For Q1.

B. Do you understand why the values marked on your graph in Post #1 are in the wrong positions?

I guess you:

i) need to include an ammeter in your circuit (assuming your software doesn’t automatically display currents);

ii) need to make some of the voltages negative which (with the source polarity as shown) to make the diode forward-biassed (if allowed you could just reverse the polarity of the supply);

iii) then take current and voltage readings enabling you to calculate the resistance of R2.

C. Can you do i) to iii)?
__________________

For Q2,

D. Do you understand why you got the frequency wrong (as noted in Post #2)? What is your answer now?

E. What is the meaning of ‘Charge’ in the Post #1 table? Do you just mean that the circuit is on?

F. Why is the capacitor not connected?

G. What voltage is being measured by the oscilloscope (where is the oscilloscope connected to)?

H. In Post #1 the voltage across R was 23.0V. In Post #3 it changed to 22.7V. Why?

I. How did you find your value for 'ripple'?

J. I realized the value of R4 is given (2kΩ). Sorry for not noticing it in Post #2. If 23V is applied across a 2kΩ resistor, what is the current in amps and in milliamps?

K. You have what is called a full-wave (bridge) recitifier. The output voltage is DC, not AC. But you have an AC voltmeter connected across R4. Is that intentional?

Can you answer questions A-K?

Edit: Typo's corrected.

 

[Noob of the Maths]

A.- The circuits cannot be changed (except for the voltage requested in the tables).

B.- The graph assumes that the values must be positioned on the positive x-axis of the voltage.

C.- The first circuit I can not put negative voltages because I must only use the values that are marked in the table (3.5, 4.5, 5.5 and 6V).

Being all positive and less than 50V, the circuit will always be open, so there will be no current flow. In this way it would be unnecessary to calculate any value in the resistance, being zero in an open circuit.

D.- Yes, I realized the error, which I corrected by changing the ms to s.

E: In this case it is the resistance value (resistance load value), it is true that it is confused, so I changed it to "resistance".

F.-My mistake, I did not connect it.

G.- The values of resistance and source must be measured with oscillator.

H.- It is answered with "F".

I.- I did not calculate this one. It is solved with the average current over the frequency and the capacitor.

J.- 12 A and 12k mA

K.- I put a DC voltmeter, but the software made crazy the value that marked, it had many intermittent changes.

 

[Steve4Physics]

The shape of the oscilloscope trace for the resistor is completely wrong and should look a bit like the thick line in this link:
https://web.sonoma.edu/users/m/marivani/es231/units/images/fig05_1.png

So there is a very serious fault somewhere. Bearing that in mind, here are my comments on your replies.
______________

A. OK. But it’s possible that the circuit in question-1 has a mistake and the polarity of the supply (or the diode) is wrong. If you are able to check this with your teacher, it would be worthwhile.
______________

B. Your graph’s voltage-axis is linear. So equal distance along the axis are equal voltage-differences. The positions of the values on this axis in your first post make no sense.
______________

C. OK (But see my answer to item A.)
______________

D. I get the period is T = 8.3ms.

______________

E. OK.
______________

F. OK.
______________

G. The peak-to-peak distance on the oscilloscope for the supply is 17 divisions. Since 1 div = 1V, the peak-to-peak voltage is 17V. So the amplitude is $V_S$ = 17/2 = 8.5V, not 24V. So there is something seriously wrong. The oscilloscope reading does not match the voltage shown.

Using T = 8.3ms (see D above) the frequency = 1/0.0083 = 120Hz (should be rounded to 2 or 3 sig figs.)

The peak-to-peak distance on the oscilloscope for the resistor is 12.6 divisions. Since 1div = 1V, the peak-to-peak voltage is 12.6V. So the amplitude is $V_R$ = 12.6/2 = 6.3V, not 23V. So there is something seriously wrong. The oscilloscope reading does not match the voltage shown.

Since the oscilloscope display is incorrect I don’t understand what the ‘ripple voltage’ means.

I don’t know how you calculated $I_R$ because you have not shown your working. Using 23.0V and 2000Ω, $I_R$ = 23.0/2000 = 0.0115A = 11.5mA (not ‘12K’!)
______________

H. OK.
______________

I. OK (though the value is meaningless because there is a fault.)
______________

J. Your calculation is wrong. As noted above, using 23.0V and 2000Ω, $I_R$ = V/R = 23.0/2000 = 0.0115A = 11.5mA.

And note, we never combine prefixes (e.g. 'k' and 'm'). It is incorrect to write 12 k mA when you mean 12A (or 12000mA).
______________

K. Assuming you have set up the circuit and values correctly there must be a serious fault in the software. This makes the problem impossible. (I may be wrong and would be pleased if anyone else had a view!)
______________

I’m going to bed now! Best wishes from the UK.

 

[Tom.G]

When you connect the capacitor, C1, in the simulation, get new readings on the oscilloscope; they should be significantly different.

These sites may help your understanding of the circuit:
https://www.electronics-tutorials.ws/diode/diode_6.html
https://lastminuteengineers.com/the-full-wave-bridge-rectifier/