DC Circuit Analysis with a Potentiometer

In summary, the conversation discusses a problem involving a resistive current source with a 10 kΩ potentiometer and a voltmeter. The speaker is unsure how to approach the problem and is seeking help. They mention using Ohm's law to solve the problem. The problem asks for the current and voltage at different positions of the potentiometer and whether the circuit represents a reasonable constant current source.
  • #1
mrdworth
1
0
I've been able to get all of the problems up to this point, but I have never seen a problem like this before, so here it goes:

9. Below is shown a simple resistive current source. The resistive load is represented
by a 10 kΩ potentiometer. What is the current through the resistive load over the
full range of the potentiometer and what is the reading on the voltmeter over the
full range of the potentiometer? Does this circuit represent a reasonable constant
current source? Why or why not (explain)?

Please see the following PDF (Question #9) for the diagram of the circuit:
http://www.engr.colostate.edu/ECE103/FA13/homeworks/Homework2%20FA2013.pdf

The only equations that I know that are useful here would probably just be Ohm's law and variants:
P=IV
V=IR
I=dQ/dt

Unfortunately, I don't know where to begin with this problem. The only true given is the voltage, so I don't know how to solve this problem.

Any help is appreciated!
 
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  • #2
Subproblems:
- what are current and voltage if the potentiometer is at the uppermost position?
- what are current and voltage if the potentiometer is at the lowermost position?
- what are current and voltage if the potentiometer is somewhere in between?

You just need Ohm's law to solve that problem.
 

1. How does a potentiometer work?

A potentiometer is a three-terminal resistor with a sliding contact that forms an adjustable voltage divider. The sliding contact, or wiper, allows for the resistance to be varied along the length of the resistor, thus changing the output voltage. It works by using the principle of Ohm's law, where the resistance and voltage are inversely proportional.

2. What is the purpose of a potentiometer in a DC circuit analysis?

The purpose of a potentiometer in a DC circuit analysis is to act as a variable resistor, allowing for the precise adjustment of voltage levels in a circuit. This is useful for calibrating electronic devices, such as volume controls in audio equipment or brightness controls in displays.

3. How do you calculate the output voltage of a potentiometer in a DC circuit?

The output voltage of a potentiometer can be calculated using the formula Vout = Vin(R2/(R1+R2)), where Vin is the input voltage, R1 is the resistance of the fixed portion of the potentiometer, and R2 is the resistance of the variable portion of the potentiometer (between the wiper and the end). This formula assumes that the potentiometer is being used as a voltage divider.

4. What is the difference between a linear and logarithmic potentiometer?

A linear potentiometer has a linear relationship between the position of the wiper and the resistance, meaning that the resistance changes at a constant rate as the wiper is moved. A logarithmic (or audio) potentiometer has a logarithmic relationship, meaning that the resistance changes more gradually at first and then more rapidly as the wiper is moved.

5. Can a potentiometer be used in AC circuits?

Yes, a potentiometer can be used in AC circuits. However, the output voltage will not be constant, as it is in DC circuits, due to the constantly changing direction of the current. The output voltage will depend on the frequency and amplitude of the AC signal.

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