If anyone could give me their answer on this question, and how they got there pls

[maxywell92]

the question i am struggling with is this, im new to the calculating of things and am not sure where to start.

A two core cable supplies two loads from a 230v supply, the first load is 70m from the supply and takes a current of 40A, the second load is 100m from the supply and takes 20A. find the voltage across the second load if each core of the cable has a c.s.a of 25mm2, assuming resistivity is 17M ohm mm.

Thanks

 

[Strima]

Try breaking the cable down into two, do some calculations as post your answers...

 

[Badged01]

do you mean 17 milli ohms per metre (not 17 mega ohms per mm?)

 

[Richard Burns]

You have got a slightly difficult one there since it is not the standard on site method of VD= (mV/A/m)*1000*A*L

The value for the resistivity (rho) should be 17 mohm.mm
Since the SI value is 1.7*10 to the power of (-8) ohm.m

Calculation is R= rho* L/A using SI units (Ohm= ohm.m * metre / Amps)
and V=IR

Try this and see how you get on doing as Strima says.