Potential Difference Across Diode & Resistor

In summary: You need to take the absolute value of Vac when it is negative, which is what the diode does. (Also, don't forget the diode drop Vt in there.)In summary, the conversation discusses finding the potential differences across a diode and resistor in an ideal diode circuit with a specified voltage and varying forward bias. The suggestion of using equivalent circuits is given and the process of finding the potential differences is discussed, including using KVL and taking into account the voltage drop and AC voltage. A diagram is provided to help visualize the circuit and the final conclusion is that the ideal diode will take the absolute value of the negative AC voltage.
  • #1
Potatochip911
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Homework Statement



Assume an ideal diode with ##V_t=0.6##v, find the potential differences across the diode V_ab and across the resistor V_bc as the forward bias voltage is varied from 0 to 10v. Hint: equivalent circuits may be useful

Embedding the image wasn't working so: http://s28.postimg.org/l6b8yzqbw/image.jpg

Homework Equations

The Attempt at a Solution


I'm not really sure how to find the potential difference across the diode and resistor. From KVL I get ##V_0=V_{ab}+iR## although this doesn't seem useful since it's an equation with both of the quantities that I want. I'm pretty sure there's no potential difference across them until the voltage increases to 0.6V though.
 
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  • #2
Potatochip911 said:

Homework Statement



Assume an ideal diode with ##V_t=0.6##v, find the potential differences across the diode V_ab and across the resistor V_bc as the forward bias voltage is varied from 0 to 10v. Hint: equivalent circuits may be useful

Embedding the image wasn't working so: http://s28.postimg.org/l6b8yzqbw/image.jpg

Homework Equations

The Attempt at a Solution


I'm not really sure how to find the potential difference across the diode and resistor. From KVL I get ##V_0=V_{ab}+iR## although this doesn't seem useful since it's an equation with both of the quantities that I want. I'm pretty sure there's no potential difference across them until the voltage increases to 0.6V though.
It looks like the question just says the diode voltage is 0.6V, so the voltage across the resistor would just be the value of the voltage source minus the 0.6V diode drop,. Seems kind of too easy, though...
 
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  • #3
berkeman said:
It looks like the question just says the diode voltage is 0.6V, so the voltage across the resistor would just be the value of the voltage source minus the 0.6V diode drop,. Seems kind of too easy, though...
Yea that's probably correct though since I'm supposed to find the ac voltage across the resistor now if the battery is replaced by an ac function generator. I'm supposed to let ##V_{ac}=V_0/sin wt## with V_0>V_t so I suppose this is also what the function generator is equal to. Now I have to graph V_{ac} and V_{bc} on the same scale versus t.
Using kirchhoffs law would it end up looking like this?
http://s11.postimg.org/818tzi9f6/image.jpg

Sorry for terrible pictures I'm on my phone
 
  • #4
Potatochip911 said:
Vac=V0/sinwt
I think you mean Vac = Vo * sin(wt)

And your drawing is basically right for the ideal diode they are specifying.
 
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1. What is potential difference?

Potential difference, also known as voltage, is the difference in electric potential between two points in an electric circuit. It is measured in volts (V) and is responsible for the flow of electric current.

2. How is potential difference calculated?

Potential difference can be calculated by dividing the amount of work done (in joules) by the amount of charge (in coulombs) that passes through a point in the circuit. It can also be measured using a voltmeter.

3. What is the potential difference across a diode?

The potential difference across a diode is the difference in electric potential between the anode and cathode terminals. This potential difference allows current to flow through the diode in one direction, while blocking it in the opposite direction.

4. What is the potential difference across a resistor?

The potential difference across a resistor is the voltage drop that occurs when an electric current passes through it. This drop in voltage is proportional to the resistance of the resistor and the amount of current flowing through it, as described by Ohm's law.

5. How does the potential difference across a diode compare to that of a resistor?

The potential difference across a diode is typically much lower than that of a resistor. This is because a diode is designed to allow current to flow in one direction, resulting in a lower voltage drop across it. A resistor, on the other hand, offers a constant resistance to the flow of current, causing a larger voltage drop.

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