Is the Scattered Voltage Data in My Experiment a Result of Measurement Error?

In summary, the conversation is about a quality of measurements coursework where the goal is to find the efficiency of a kettle. One of the factors needed to be measured was the voltage. The voltage values were found to be scattered and it was questioned if this was normal or if the experiment was done incorrectly. The expert provided information about the difference between voltage and power and explained that the mains voltage is usually constant but can vary for various reasons. They suggested calculating the average voltage and using that for the experiment. The conversation also touched upon the relationship between voltage, current, and time in determining energy. Ultimately, it was concluded that in this particular experiment, there may not be a relationship between voltage and volume or current and volume. The expert also suggested looking
  • #1
physicsnerd26
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I'm doing a quality of measurements coursework at the moment, the coursework was to find the efficiency of a kettle, and to do this, one of the factors that I needed to find was the voltage.

So in 300ml of water, the voltage was 240.5V
400ml - 244V
500ml - 243V
600ml - 245V
700ml - 241.4V
800ml - 242.8V

I tried to graph it and it was completely scattered, I was just wondering if this would be normal, or does this mean that I did my experiment wrong?
 
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  • #2
It sounds like you are measuring the voltage provided by the wall outlet that powers the kettle. One would not expect the mains voltage to vary significantly based on the amount of water in your kettle.
 
  • #3
jbriggs444 said:
It sounds like you are measuring the voltage provided by the wall outlet that powers the kettle. One would not expect the mains voltage to vary significantly based on the amount of water in your kettle.

So I did it wrong? I used a plug-in power meter and recorded the voltage of each amount of water at the first minute everytime actually, not sure what went wrong there.
 
  • #4
Voltage and power are not the same thing. Voltage is a measure of how much energy each unit of current will deliver. Unless you also measure how much current is being provided, it tells you nothing about how much power is being used.
 
  • #5
I tried to graph it and it was completely scattered...

That tells you there is no relationship between voltage and volume. If it had been a nice straight line that might have indicated they were related.

Your results are exactly what you would expect. The mains voltage is more or less constant but can vary moment to moment for a number of reasons unrelated to your experiment.

One option would be to calculate the average voltage and use that.
 
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  • #6
jbriggs444 said:
Voltage and power are not the same thing. Voltage is a measure of how much energy each unit of current will deliver. Unless you also measure how much current is being provided, it tells you nothing about how much power is being used.

I also did the current. And the graph I made for it is just as scattered as the voltage.
 
  • #7
CWatters said:
That tells you there is no relationship between voltage and volume. If it had been a nice straight line that might have indicated they were related.

Should there be a relationship between them? I kinda get the feeling there should be, just not too sure since I'm not too familiar with the whole voltage and stuff.
 
  • #8
Power and energy are not the same thing. Power is how much energy is delivered per unit time. Unless you also measured the time, it also tells you nothing.

Edit: I should have made it more explicit that if you multiply voltage by current you get "power".
 
  • #9
jbriggs444 said:
Power and energy are not the same thing. Power is how much energy is delivered per unit time. Unless you also measured the time, it also tells you nothing.

I measured that too, the time seemed about right, there was an increasing pattern there, my problem is the voltage and current being in a completely weird order.
 
  • #10
physicsnerd26 said:
Should there be a relationship between them? I kinda get the feeling there should be, just not too sure since I'm not too familiar with the whole voltage and stuff.

No. In this experiment I would not expect a relationship between voltage and volume or current and volume.
 
  • #11
CWatters said:
No. In this experiment I would not expect a relationship between voltage and volume or current and volume.

Okay, thank you.
 
  • #12
It takes Energy to heat water. The more water you have to heat the more energy you need..

Energy = Power * Time
and
Power = Voltage * Current
so
Energy = Voltage * Current * Time

If Voltage and Current are constants then Time is a measure of the energy required. Try plotting Time vs Volume.
 
  • #13
Of course if voltage and current vary slightly and randomly then a plot of energy versus volume should correlate even better.
 
  • #14
physicsnerd26 said:
I'm doing a quality of measurements coursework at the moment, the coursework was to find the efficiency of a kettle, and to do this, one of the factors that I needed to find was the voltage.

So in 300ml of water, the voltage was 240.5V
400ml - 244V
500ml - 243V
600ml - 245V
700ml - 241.4V
800ml - 242.8V

I tried to graph it and it was completely scattered, I was just wondering if this would be normal, or does this mean that I did my experiment wrong?
I see that the course content is about quality of measurements. Presumably this means you'll be investigating things like measurement error, random errors, systematic errors, and accuracy versus precision in measurements.

Your voltage values may vary the way they do for any of several reasons. For example the device used to measure them may be flawed, exhibiting poor repeatability (precision). Or the voltage meter may only give readings accurate to 2% on the chosen scale. Or the meter may have been analog and different people made the measurements from different viewing angles of the meter. Or the voltage may actually be varying over time due to reasons entirely external to your experiment!

Whatever the reason you can try to figure out if the variations point to accuracy or precision issues in the experimental data.
 

1. What is voltage of electricity?

Voltage of electricity is the measure of the electrical potential difference between two points in an electrical circuit. It is also known as electrical pressure, as it is responsible for the flow of electric current.

2. How is voltage of electricity measured?

Voltage is measured in units called volts (V) using a device called a voltmeter. It can be measured at any point in an electrical circuit, and the voltage reading will vary depending on the components and their arrangement in the circuit.

3. What is the relationship between voltage and current?

Voltage and current have an inverse relationship, meaning that as voltage increases, current decreases and vice versa. This relationship is described by Ohm's Law, which states that voltage is equal to current multiplied by resistance (V=IR).

4. What are the effects of high voltage in an electrical circuit?

High voltage can be dangerous and can cause electric shocks, burns, and even death. It can also damage electrical components and cause fires. Therefore, it is important to handle high voltage circuits with caution and use appropriate safety measures.

5. How is voltage of electricity used in everyday life?

Voltage is used in everyday life to power various devices and appliances, such as lights, computers, and kitchen appliances. It is also used in power grids to distribute electricity to homes and businesses. Without voltage, we would not be able to access the benefits of electricity in our daily lives.

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