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# Formula Help.

Discuss Formula Help. in the Electrical Forum area at ElectriciansForums.net

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#### Vassy

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Hi, A simple question. I am studying to be an electrcian and finding the books sent to me dont explain the formula's very well.

For example, one of the questions is: An electric lamp has a filament resistance of 534 Ohms when connected to a 230V supply. The current flowing through it would be?
I have done the maths using the fomula of I = V/R and the answer is 0.430
How would this be written, for example. would the reading be 430mA (milliamp) or do I just ignor the 0. bit ??

I would e mail my tutor but last time it took over a week for them to get back in touch with me.

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J

#### JulesHurley

Vassy

Technically either answer would be correct, but remember that the use of the correct unit symbol is important. You will need to ask you tutor what format needs to be used for your exams, as marks may be deducted. Dont develope bad habits.

ie 0.43A is the same as 430mA, and, 12000W as the same as 12kW, but how will an examiner mark your paper.

At least you understand VIR, trust me, I've had third years who couldn't.

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#### Vassy

Thanks for your help, & a speedy reply. I do wish i didnt work away from home so could take night classes. I dont Find the study ooks that helpfull on some of the stuff...Tend to clear up what i dont understand from the books on line, in fact finding the web more help than the books on formula issues.

Thanks again
Vassy

Thanks Jules. The books I have dont tell you what format the answer should be in. I did understand I must use the correct symbol's, Ididnt write them in because wnted to know which I should be using. But you are right, I should always use them, even in notes so I dont get into bad habbits. I will send an e mail to my tutor asking which I should be using.

Thank you very much for your help....and the slap on the wrist

Vassy

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#### Steve D

Hi Vassy,

I'm at college as well, 3rd year of 2330.

I would probably think that your tutors would prefer you to use the 430mA option instead of 0.43A as it helps to show more of an understanding rather than just 'writing down what it says on the calculator.

Good luck with the course.

Feel free to PM me if you ever have any queries on the course theory as you're probably doing the same course as me.

Cheers
Steve

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#### Vassy

Thanks Steve,
Wish I didn't work away from home so i could do the night classes, Would find it much easier I'm sure. Thanks for your advise, I wasnt sure which to write in so decided on both in the end 0.43A and 430mA. I was just wondering if there was some sort of unwritten rule that says which i should use. For instance if under 1amp then should be in mA. Thanks for your offer of help too, will be in touch & good luch with your course.

Vassy

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#### Steve D

I don't believe there's any unwritten rule as such.
They mean the same thing but by showing a fraction of an amp as a value in mA then I'm sure an exam marker would prefer it (they wouldn't mark you down either way though).

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#### Vassy

Thanks Steve D.

I just went with the "If I put both down they cant grumble", & shows I understand what I'm on about.

Vassy

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#### Steve D

Yeah I agree.

In a written exam answer, I would normally write the answer as = 0.43A = 430mA

I tend to go over the top with written calculation answers and write down every single step and formula etc, partly to help my future revision and partly to 'show' that I know what I'm on about from a marking point of view.

As a tip, when you're writing a page of calculations to get a final answer it is useful to anally keep writing down the formulae as you go. You may know the formula off by heart now, but in a couple of years time you may forget it, so I've found if you keep writing the formulae down it helps to stick.

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#### Vassy

Thanks Steve D, I think of most things I do in life like approached my martial arts training. The art is boiling water and the training is the heat. need to keep training to maintain a boiling point. A bit deep but if you understand what I'm saying will know what I mean. Keep applying all parts of your study and will soon become second nature.

Another problem I am finding is how should I be aproaching some of the questions. For example,, a question I am asked is : A service engineer suffered a fatal electric shock when he touched a metal sink. Investigation revealed that an electrician working in the same property had mistakenly connected a live conductor to an earth terminal. Two of the electricity at work regulations that were possibly contravened are?

I have found three that it could be, depending on the interpretation of Electrician. For instance, The three regulations I have found are.
1: Regulation 4, Systems, work activities and protective equiptment.
2: Regulation 15, Working space, access and lighting.
3: Regulation 16, Persons to be competent to prevent danger and injury.

If someone is to be called an electrician they should be trained to a high enough standard to carry out thier duties. Which would meen that regulation 16 isnt an issue but regulation 15 could be if inadequate lighting was supplied for work to be carried out safely. I'm not asking for an answer,I would sooner find that myself. I would just like to know if I'm looking to deep into the question.

Thanks
Vassy

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P

#### pushrod

What level are you doing? are your exams not multiple choice? If they are there will be no problem as you understand the idea of mA and A - they will not give both 0.43A and 430mA as possible answers. From the multi choice exams i have seen a couple of the answers can very easily be discounted.

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#### Vassy

Sorry I keep forgetting to put the course details. The course is a study at home course with ATC trade skills learning. The course is the Professional Electrician Course which includes. Part P EAL Cert, City & Guilds 2382, City & Guilds 2392-10 and City & Guilds 2391-10. The course is split into four module's. Module 1 covers Introduction to basic maths and electrical theory, 1st section of part P Domestic installer's scheme. 5 day classroom and workshop based.

Module 2 covers final section of the part P Domestic Installer's scheme (EAL Full Scope). Exam: Part P Domestic installer, 5 day classroom and workshop based.

Module 3 covers 17th Edition IEE Wiring Regulations Cert. Exam: City & Guilds 2382, City & Guilds 2392-10. 5 days classroom and workshop based.

Module 4 covers Testing and certification of electrical installations. Exam: City & Guilds 2391-10 5 day classroom and workshop based.

I am currently on my 1st module studying when can due to heavy work load.

Thanks
Vassy

#### jeremy

##### -
Mentor
Arms
Evening all! When I were a lad if the question was asked in a certain unit , then it should be answered in the same unit; if the unit of the question is unclear then SI units should be used. This is only my opinion not advice as if I wanted to be constantly criticised I would have stayed married

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#### Vassy

lol cheers Jeremy. I've answered with both. It's my home theory book I am working from so any mistakes will be pointed out when i go for my 1st weeks practical workshop and classroom session. I hope anyway.

Vassy

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#### pushrod

Hi Vassy that course sounds hard especially with a lot of it being home study. How long do you expect it to take?

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#### Vassy

Hi Pushrod, I dont have a completion target date as It all depends on my workload. I am a telecomms engineer (contractor). Sinse I started my course work has taken off loads and I dont get that much time to study because work 14hr days (off the record). I have just got home again sinse my last post. I manage to fit an hour of study in a day while at work and hit it hard when I'm at home.I hope to have the 1st two modules out the way this year.and the 2nd two between another year to a year and half.

In my trade the work does stop for a few months of the year and thats when the study will pick up to about 6 hours a day at least. Always wish I could study at college but circumstances dont permit.

Vassy

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