ELECTRICAL CALCULATORS (.xls
files) © K.Brown 2025
About the calculators
The ELECTRICAL CALCULATORS have been designed
specifically for Electrical Installation courses (2330/2365/2357) – all Levels,
and are Microsoft Excel files (.xls)
2)
One set of calculators has been designed to work on Windows pc’s and laptops (XP/Vista)
that run Microsoft Excel (2003 or later). Another set has been specifically
formatted for APPLE MAC desktops (iMac)
and macbooks (running the OSx operating system and Microsoft Excel for
mac). These versions have protected cells to prevent accidental deletion of
formulas etc)
3)
NOTE: some windows notebooks and apple ipads only have
an Excel ‘viewer’ bundled with them. As this is NOT a ‘full’ version of
Microsoft excel these VIEWERS WILL NOT BE ABLE TO MAKE FULL USE OF THESE
CALCULATORS. NEITHER WILL SMARTPHONES (iphone or android). As these viewers are
effectively ‘read only’ applications you are not able to input any numbers into
the calculators.
4)
Ipad users who have NUMBERS software installed (NUMBERS is
the ipad version of Excel) WILL BE
able to open and use the calculators – however, because numbers does not allow
any cells to be protected, there is the very real risk that important cells
could accidently be deleted by the user (you) – so I recommend that a copy of the calculators is saved
somewhere on your ipad so you always have a ‘master set’ – in case of an
accidental deletion in your ‘working set’.
5)
There is a windows AND an apple ‘demo calculator’ for
you to download and ‘try-before you-buy’ – to ensure compatibility with your
pc/mac/ipad etc. The link is on the website.
There are calculators for Twelve Topic areas, containing 35 separate calculator tabs,
giving so 35 individual calculators in
total covering ALL topic
areas in the electrical installation courses.
Calculators are available
for the following TOPIC Areas;
·
DC circuits - Ohms Law, resistors in series, resistors
in parallel, full circuit calculations including power, currents, volts-drops.
Resistivity including micro, nano and area conversions. Temperature
coefficients of resistance.
·
Mechanical science – Force, Mass, acceleration,
velocity, pressure, Work done, Power. Levers and balance, effort and load,
efficiency.
·
Cable sizing calculations - including earthing checks
·
AC circuits – R,L and C calculations in series and
parallel, Inductive and capacitive reactance (XL and Xc), Impedance, true
power, apparent power, reactive power, Pythagoras theorem, power factor (Cos0),
voltages and currents, STAR and DELTA voltages and currents, calculating
Neutral current in unbalanced STAR systems.
·
Transformers – calculating step-up and step-down
voltages, currents and number of turns. Calculating transformer efficiencies (3
different ways).
·
Magnetism and Inductance – magnetic flux density, core
area and magnetic flux. Force on a conductor and back EMF. Stored energy
calculations. Self and Mutual inductance calculations.
·
AC motors and generators – Synchronous speed,
frequency and poles. SLIP calculations, rotor speed, rpm and rps conversions.
·
DC motors and generators – Lenz Law, Terminal voltage
and back EMF calculations, Armature current and Resistance calculations.
·
Motors (Advanced) – Torque in AC motors, Torque in DC
motors, belt speeds, conveyor dimensions, gear-feeds, friction, efficiency, rotor
speeds, gearhead ratios.
·
Lighting – Inverse Square Law, Illumination,
Illuminance, Cosine Law, Pythagoras theorem, total Luminous Flux and number of
lamps required, efficacy, Coefficient of utilization and maintenance factors.
These calculators
can calculate the answer for ANY maths questions from the above topics.
Saving and opening your calculators (from email to your pc/mac)
6)
On your pc/laptop/mac, locate your calculators and
Open the TOPIC calculator that you want to use.
1)
The calculator will load up in your Microsoft Excel
program. Select the appropriate calculator TAB located on the bottom of the
page (note that you may not see all the tabs available on your screen depending
on your screensize. Be sure to click along the tabs to ensure you are able to
see and access all available calculators using the scroll buttons as shown
below).
On Imacs, you can minimize
the EXCEL window so you can see all the tabs (because apple program icons may
be in the way along the bottom of the screen).
How to use the calculators
1)
Type your values from the question into the
appropriate WHITE cells on the calculator (see below).
2)
Answers will be shown in the YELLOW cells.
3)
ALL coloured cells are locked to prevent you from
accidentally deleting the formulas hidden in those cells. (Ipad users with
NUMBERS software - you CAN
accidently delete important coloured cell contents – SO AVOID coloured cells
completely)
4)
Some answers are also displayed in the diagrams on the
calculators.
Useful info about entering
values on the calculators
1)
Only valid numbers can be typed into the white cells.
These include decimal points and decimal numbers (i.e. 12.695 etc), negative
numbers (i.e. -0.005), and numbers to the power of 10 (i.e. 25.8x109
or 16.6x103).
2)
Some calculators require values to the power of 10 or
give answers in this form (i.e resistivity, pressure, area conversions from mm2
to m2 etc). Microsoft Excel makes it very easy to enter or
receive numbers in this way. Some examples are shown below (some detail is
shown on the actual calculators also);
245µA is equal to 245x10-6. In
Excel, type it in as 245E-6
66.68nF is equal to 66.68x10-9. In Excel, type it in
as 66.68E-9
132kV is equal to 132x103. In Excel, type it in as
132E3
50M ohms is equal to 50x106. In Excel, type it in as
50E6
What
if?........Questions and Answers
·
Will these calculators work on windows and mac
computers?
I have produced a set of
calculators for windows pc’s and laptops (running microsort excel) AND a set of
the same calculators specifically formatted for Apple Imac – so it is important
that you ensure you use the correct ones
(you specify this when you buy).
I cannot guarantee that
these calculators will work on any iphones and other smartphone devices, or
tablet pc’s. To be sure, I recommend that you download the free ‘demo’
calculator and try it out for yourself. There is a ‘demo calculator’ available
for windows
·
Can these calculators be saved or printed out?
Yes, calculators can be (and
should be) saved to your pc/laptop anyway on receipt. (Its always best to save
a copy of the calculators somewhere safe – so you always have a master set).
You can print out the calculators at any time remembering to format the pages
depending on your printer type etc.
·
How accurate are the calculator answers?
Extremely accurate. As
answers are calculated using the mathematical formula for the respective topic.
Answers are always 100% correct. Most answers are given to at least two, three
or more decimal places, or rounded up where necessary.
·
What if I want to type a value into one of the
coloured cells?
On Mac and PC You cannot do
this. All coloured cells are locked because they contain the formulas required
to calculate the answers. If you were able to access these cells you may
accidentally delete/overwrite/corrupt the formulas and the calculator would no
longer work.
You only have access to the
blank white cells, but this should enable you to calculate/find ANY missing
answer or you can transpose (rearrange) the standard formula or use the ‘trial
and error’ approach (as a last resort) see the end of this doc for more
information on this.
Ipads
using NUMBERS software please note: cells are
UNLOCKED (as standard) so it is possible to type anything anywhere
(possibly deleting important formulas etc). Keep a ‘back-up copy’ of the
calculators just in case.
·
What do I do when I’ve finished using the calculators?
It’s best to just close them
down WITHOUT SAVING. That way the calculator cells are empty ready for the next
time you need to use the calculator. However, you can opt to SAVE a calculator
at any time if you were halfway through a calculation – its up to you.
·
How useful are these calculators to me as an
electrical installation student/apprentice?
It’s like having a friendly
maths teacher with you to mark your work! – No only do they show you the
standard formula, but they will work out ANY answers you need for any maths
question given on the topic concerned, often displaying answers on circuit
diagrams also. Useful for checking your completed calculation answers. They
also allow you to create your own questions – then use the calculator to mark
them !
These are dedicated
calculators specifically designed for electrical installation maths and science
topics.
·
As a Lecturer/Tutor, how useful can these calculators
be?
Incredibly useful – because
they can accurately answer ANY calculation question instantly they will allow
you to issue different questions (values in the questions) to different
students depending on their level of ability. This is DIFFERENTIATION which is
a core requirement in OFSTED guidelines.
A question paper devoid of
any number values can be quickly printed out for a class of 14 students. I
personally write in some different number values, by hand, onto each question
paper (based on student ability etc) then issue in class. Marking them can be
done several ways;
1)
Whilst generating the question papers, input the
chosen question values into the calculator then print out the completed
calculator sheet (showing question values and answers) to use in class later
(or mark with later).
2)
Mark as a class task - students swap completed
differentiated papers, then each one reads out the number values for question
which teacher then types into calculator on a whiteboard thus displaying
answers which student then marks OR issue ‘printed’ calculator sheets for
students to check against. Alternatively, students input values into calculator
on whiteboard in front of class.
3)
Collect the papers in to mark later by simply typing
the question values into the calculator for instant answers.
4)
Print out sets of complete questions WITH answers –
and get students to carry out the calculations (working-out), showing that
their answers match the printed answers as shown by the calculators.
5)
They also provide a valuable time-saving tool for
lecturers/teachers/ tutors when it comes to marking (or creating)
differentiated questions, or marking/checking tutor-written calculation
exercises and exams.
·
What if students with access to these calculators just
use the to answer maths questions in assignments, homework etc without actually
doing the calculating?
That’s an easy answer. In
order to measure a students’ ability to carry out the calculations, the method
they used (transposition, unit conversion, working-out) is far more important
than the answer they give. I always issue far more marks for the ‘working out’
than for the actual answer. Students are therefore encouraged to provide their
working-out because of this. For example; a 10 question exercise carries 50
marks and a minimum pass-mark of 65%. One mark is awarded for each correct
answer but 4 marks extra for each question that shows all the correct working
out, formula rearrangement etc. Anyone just using the calculator to arrive at
answers would get 10/50 (20%) which is a Fail.
These calculators are a
tool. They allow students to check their answers once they have carried
out their calculations.
·
Am I allowed to copy or modify these calculators?
These calculators are LOCKED
worksheets (to protect the calculation functions from accidental
deletion/corruption) so cannot be modified easily. Whilst they can be copy and
pasted into new Microsoft excel spreadsheets, none of the calculation scripting
is copied.
·
Are there any time-limits or Passwords when using
these calculators – like there are with downloaded materials from your website?
There are NO
time-limits associated with these calculators once you have saved them to
your own pc – they are yours to use –
forever.
There are passwords that LOCK the coloured
cells on the calculators – but that is to prevent accidental deletion of the
formulas, which would stop the calculator working. I won’t issue the passwords
because of this.
·
What if I have a question where the answer has already
been given to me, and I need to find one of the other values as the answer?
Some of the calculators
contain rearranged formulas (transposed) so you can find out whatever you are
trying to calculate be selecting the appropriate calculator. However, if this
is not always available so you can either TRANSPOSE (rearrange) the standard
formula yourself on paper OR use the ‘trial and error’ approach with the
calculator.
Each calculator displays the
formula(s) used in that calculator, so you should really attempt to transpose
(rearrange) them, as required.
If using the ‘trial and
error’ approach.
For example, in AC circuits
the formula for Z = √R2+Xc2. If you were given ohms
values for R and Xc and were asked to calculate the value of Z you would simply
type the values for R and Xc into the calculator cells and the answer for Z
would be displayed
.
However, if you were given
the value of 5 ohms for Z (the
answer in other words) and also given the value of R (3 ohms for example) and you were asked to calculate the value of Xc
as an answer, just type the value given for R (3 ohms for example) into the calculator and choose any number to type into Xc. Look
at what answer you get for Z to see if it is 5 ohms (very unlikely on the first attempt). In the example
below, I chose 3 ohms for Xc and Z becomes 4.243 ohms.
If Z is not equal to 5 ohms (which is isn’t in my example)
choose either a higher or lower value to use for Xc and type it in. Look again
at the answer given for Z. Is it closer of further away from the (expected) 5 ohms answer that it should be. In my
example below, I chose a lower value than 3 ohms (1.5 ohms) and Z went even
lower than the 5 ohms I need.
Keep varying the value for
Xc until Z=5 ohms until you find the value for Xc required for Z to equal 5
ohms. In my example, I chose a higher value for Xc this time than the 3 ohms I
tried first. I found that a value of 4 ohms for Xc gives exactly 5 ohms for Z (see below).
This ‘trial and error’
method will work in any calculator but of course, its preferable for you to be
able to TRANSPOSE (rearrange) any formula yourself rather than use the ‘trail
and error’ approach.
Close this window to return to the last page you were on.
(END)
K.Brown © 2025