Stuck on a Question, please Help :)

[adambrookes1]

Hi there guys, I am currently stuck on a question which I need to answer so I can continue my coursework.

I have uploaded a image of the paper and the 3 questions I need to answer, please can someone explain to me how I calculate the answer to the question so I can do it please.

 

[Pete999]

Have you actually tried to do the calculation? I only ask because being a mentor and retired it's a long time since I did these calcs and it looks quite easy.
Perhaps if you have a bash and show us the answers, you may get some help, mentors don't like it, or at least this one doesn't when it seems like you are just asking for the sake of asking, have a go as a trainee you won't get any grief for getting it wrong (if indeed you have), it's not as hard as it looks honest, don't be scared to try we all had to learn, some of us still learning.

 

[adambrookes1]

Thanks for your reply Pete999.

My assumption on the R1+R2 is that for circuit 1 is =

R1 being 6.0 + R2 being 2.5 = 8.5 -
(6.0+2.5=8.5)
so R1+R2 = 8.5

I have never had to do these calculations before and having completed 11 TMAs I haven't had any reading that refers to these calculations.

 

[Simonslimline]

Thanks for your reply Pete999.

My assumption on the R1+R2 is that for circuit 1 is =

R1 being 6.0 + R2 being 2.5 = 8.5 -
(6.0+2.5=8.5)
so R1+R2 = 8.5

No you don't do it like that mate. Here is a pointer underneath.

6.0mm2 is the cross sectional area of the Line conductor (R1). 2.5mm2 is the cross sectional area of the circuit protective conductor (R2).

You need to look at the milliohms/m value and also the length of the circuit mate.

 

[Leesparkykent]

The chart on the left gives you the the R1 plus R2 resistance per meter in milliohms the measured values are in ohms. To find the calculated value you have to times the milliohm per meter value by the length of the circuit given in the above chart and then convert this value from milliohms to ohms. Work this out for all 6 circuits then compare the measured and calculated values. Why do you think a measured value could be higher than the calculated value?

 

[telectrix]

as a starter, for the 6.0/2.5mm cable @ 5m. the value should be (10.49 x 5)/1000. work this out and see how it differts from the measured value, then think why.

 

[adambrookes1]

Thanks for all your help guys, I think I have got it now with all your help

 

[Simonslimline]

Good stuff.

What could be the reasons for the difference in calculated and measured values do you think?

 

[adambrookes1]

Good stuff.

What could be the reasons for the difference in calculated and measured values do you think?

I am assuming resistance ?

 

[Simonslimline]

The measured value for circuit 3 is 0.35Ω.

What is the calculated value?

What could be the cause for the difference in the results?

 

[Bobster]

I am assuming resistance ?

What can alter the resistance of any metal?

 

[Simonslimline]

I am assuming resistance ?

What could be the reason/s why the resistances dont match between calculated and measured values though?

 

[adambrookes1]

The measured value for circuit 3 is 0.35Ω.

What is the calculated value?

What could be the cause for the difference in the results?

0.1951 - Reason for difference, could be, either: Resistance, Damp or maybe a faulty MVT ?

 

[Simonslimline]

0.1951 - Reason for difference, could be, either: Resistance, Damp or maybe a faulty MVT ?

The milliohm per metre values for each cables R1+R2 is based on a temp of 20c.