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Physics Quantitative OCR Question

It is suggested that the relationship between 1/I and x is:
1/I = (ρ/AV)x + k

where ρ is the resistivity of the wire, A is the cross-sectional area of the wire, V is the potential difference of the power supply and k is a constant for the circuit..
Using the value for the gradient and your other results determine a value for the resistivity ρ with an appropriate unit.

Does anyone know how to answer these type of questions? I have my coursework tomorrow. All I know is that it has something to do with y = mx +c

Reply 1

lerjj

Original post by Elhamm

In general, this type of question requires you to linearise the suggested relationship.

Ex. E_k=\dfrac{1}{2}mv^2
you need this to be a straight line so you can find out the mass by measuring the gradient. So you plot kinetic energy on the y-axis and v^2 on the x-axis.

For your equation you need to pick something for y to equal and something for x to equal. Then the gradient will be resistivity (or some multiple of it).

Reply 2

FemaleBo55

Original post by lerjj

In general, this type of question requires you to linearise the suggested relationship.

Ex. E_k=\dfrac{1}{2}mv^2

you need this to be a straight line so you can find out the mass by measuring the gradient. So you plot kinetic energy on the y-axis and v^2 on the x-axis.

For your equation you need to pick something for y to equal and something for x to equal. Then the gradient will be resistivity (or some multiple of it).
How would I work out the units required using my equation?

Reply 3

lerjj

Original post by Elhamm

How would I work out the units required using my equation?

Units for what? To work out units you can use the rules

•

both sides must have the same units

•

any time you add two quantities, they must have the same units (you can't add metres to kilograms)

Reply 4

FemaleBo55

Original post by lerjj

Units for what? To work out units you can use the rules

•

both sides must have the same units

•

any time you add two quantities, they must have the same units (you can't add metres to kilograms)

For finding resistivity.
I tried solving this equation but I was still unable.
can you please show me how to work it out step by step using any example figures for y-axis, x-axis and gradient??

Reply 5

lerjj

Original post by Elhamm

What do I and x stand for?

Assuming that you have measured: I, A, V, and x for some experiment the way to check if your relationship is true is to construct a graph which should be a straight line.

Straight lines are in the form y=mx+c
your's is in the form (1/I)=(some numbers)x+k

do you see the similarity?

Reply 6

FemaleBo55

Original post by lerjj

I stands for current and x stands for the lenght of the wire

Reply 7

lerjj

Original post by Elhamm

I stands for current and x stands for the lenght of the wire

Ok, basically what you have to do is choose something for y to equal and something for x to equal when you plot your graph- in this case you would most likely plot 1/I on the y axis and x on the x axis.

Look at your function and see if you can tell what the gradient and y intercept of the resulting line will be.