Science Buddies: "Ask an Expert"

Dear sir/ma’am

As per the experiment, during recording on the wire, we have to measure the voltage on the output terminal Of the amplifier and the resistance of the coil. Using the formula I=V/R, we can work out the recording current. This means that our current is the dependent variable and voltage our independent variable as resistance is constant. But, when I plot the graph for Current (Y axis) vs Voltage (X axis), the graphs gradient does not give me the resistance.

Therefore, I am confused as to which variable out of the voltage and current is the dependent variable and independent variable.

Also, advise me on the independent variable and dependent variable while playback as well.

I need to submit my project on Tuesday. So, your quick assistance will be appreciated.


[Project: https://www.sciencebuddies.org/science- ... -on-a-wire]

Hi Venum,

Firstly, you are correct in stating that current (I) is the dependent variable while voltage (V) is the independent variable in this case. The reason that the graph's gradient is not giving you the proper resistance is that, for an IV graph like yours, the resistance is not merely the value of the line's gradient. Instead, the resistance is found by dividing 1 by the gradient of the line (1/gradient).

For example, if you plot a voltage of 6 V on the x-axis and a current of 2 A on the y-axis, you will find that the gradient of the line is 1/3; obviously, this does not match the actual resistance, which is 3 Ω (R=6V/2A). When you divide 1 by the gradient (1 divided by 1/3), you obtain the correct resistance value, 3.

I hope that this has proven helpful; if you have any more questions, please let me know.

cvionis

Hi cvionis,

Thanks a lot for your assistance. It helped me a lot.

Venum

Dear Sir/Ma’am

Due to the Coronavirus Epidemic, I am unable to build the actual wire recorder but I am still required to create a design task with results.

Is it possible for anyone to give me possible Input Voltages with a value of constant resistance that I can use to calculate the Recording Current.

Also, could I get values for the Replay Voltage that I can use and also the reason why the Replay Voltage would be less than the Input Voltage.

Hello Venum,

I've merged your most recent post with the thread for your previous posts. This helps to alert the previous expert who has been helping you that you have a new question! Please keep your posts in this thread.

Thanks!
Madeline
Moderator

Hi Venum,

I spent some time researching wire recorders, and looked for examples of input voltages or resistance values for them. However, I was ultimately unable to find anything even close to answering your question. Perhaps you could consult your teacher or instructor who assigned the project regarding this issue.

cvionis

Hi cvionis

Thanks a lot for your help. Much appreciated

Venum