Finding out internal resistance of a lemon when used as a power supply

In summary, the conversation discusses an experiment in Physics to determine the internal resistance of a lemon used as a power supply. The method involved connecting the lemon to a voltmeter, ammeter, and variable resistor, and measuring voltage and current against each other. The individual also mentions having a table and graph of voltage against current, and asks for help in finding the EMF and intercept of the graph. The response suggests zooming out the graph scale to make the intercept visible.
  • #1
Dearster
4
0
Hi There,

Right I recently did an experiment in Physics to find out the internal resistance of a lemon when used as a power supply.

We connected the lemon to a voltmeter, ammeter and variable resistor, changed the resistance on the variable resistance and measured the voltage and current against each other.

So i have a table of voltage against current.

I have drawn a graph of voltage against current, voltage on y axis, and current on the x axis. And drawn a line of best fit. Voltage is in milli volts, 10^-3 and current is in micro volts 10^-6

How would i go about finding the EMF and eventually the Internal resistance of the lemon when used as a power supply.

Also how would i go about finding the intercept of the graph if the line of best fit does not go through the y-axis on the scale i have used.

Anything to help would be fantastic

Thank you in advance.
 
Physics news on Phys.org
  • #2
The intercept is the point at which the line crosses the Y axis.
This would be the voltage with no current (hint what's the definition of the emf of a cell?)
The slope of the graph is voltage/current, ( hint what's ohm's law?)
 
  • #3
Dearster said:
Also how would i go about finding the intercept of the graph if the line of best fit does not go through the y-axis on the scale i have used.

A straight line must pass through the y-axis somewhere if it's extended far enough, unless it's vertical (and therefore parallel to the y-axis).

I suspect you need to "zoom out" your graph scale so the intercept is actually visible on the graph.
 

1. How can I measure the internal resistance of a lemon used as a power supply?

To measure the internal resistance of a lemon, you will need a voltmeter and an ammeter. Connect the voltmeter in parallel with the lemon and the ammeter in series with the lemon. Then, take measurements of the voltage and current when the lemon is used as a power supply. Use Ohm's law (R = V/I) to calculate the internal resistance of the lemon.

2. What factors can affect the internal resistance of a lemon when used as a power supply?

The internal resistance of a lemon can be affected by various factors, such as the type of lemon, the freshness of the lemon, the size and shape of the lemon, and the method used to extract the juice. These factors can affect the amount of juice and electrolytes available in the lemon, which can impact its conductivity and therefore its internal resistance.

3. How does the internal resistance of a lemon compare to other power sources?

The internal resistance of a lemon is typically higher than other power sources, such as batteries or power outlets. This is because lemons have a lower concentration of electrolytes compared to chemical batteries. However, the internal resistance can vary depending on the factors mentioned above.

4. Can the internal resistance of a lemon change over time?

Yes, the internal resistance of a lemon can change over time. As the lemon ages and loses moisture, its internal resistance may increase. Additionally, if the lemon is squeezed or manipulated in any way, it may affect the distribution of electrolytes and change the internal resistance.

5. How accurate is measuring the internal resistance of a lemon as a power supply?

The accuracy of measuring the internal resistance of a lemon as a power supply can vary depending on the equipment used and the method of measurement. It is important to ensure the voltmeter and ammeter are properly calibrated and to take multiple measurements to get an average value. Additionally, the internal resistance of a lemon may change over time, so it is important to take measurements at the same time for accurate comparisons.

Similar threads

Putting internal resistance in series with a voltage source
    • Electromagnetism
Replies
10
Views
1K
Internal resistance proportional to current?
    • Electromagnetism
Replies
3
Views
3K
B Troubleshooting Battery Internal Resistance Measurements
    • Classical Physics
4
Replies
105
Views
7K
I Power Loss Due to An Eddy Current
    • Electromagnetism
Replies
3
Views
1K
Sizing an Isolation Transformer for a DC Power Supply
    • Electrical Engineering
Replies
8
Views
1K
Variable vs constant power supply
    • Electrical Engineering
Replies
32
Views
865
Fried my power supply by doing a bad thing
    • Electrical Engineering
2
Replies
36
Views
2K
Manually charging batteries
    • Electrical Engineering
Replies
11
Views
204
I An attempt to understand the associated variable conventions in circuits
    • Electromagnetism
Replies
1
Views
823
Question about measuring the internal resistance of power supplies
    • Electrical Engineering
Replies
8
Views
4K

Hot Threads

Recent Insights

Back
Top