Trainee questions to answer

[jimmyray]

Apologies for delay, busy weekend! I've copied this from one of my activity sheets:-
4

For the circuit above, calculate:
a) total resistance
b) value of resistor R[SUB]2[/SUB]
c) value of voltage V[SUB]1[/SUB]
d) value of voltage V[SUB]3[/SUB]
Calculate; A) Total resistance. B) Value of Resistor R2. C) Value of Voltage 1. D) Value of Voltage 3.

 

[jimmyray]

Struggling to get an image up, so I'll try to describe the circuit as best as I can. Three resistors are in series, with R1=60 ohms, R2= unknown, R3= 12 ohms. Circuit current is 5 Amps, and Supply voltage is 480 V dc. The voltage across R2=120 V. Hope you can visualise this OK. Any problems, give me a shout. Cheers. Jim

 

[pennychew]

Hi mate, daft question but are you clicking the 'insert image' button just above where you type a quick reply?

 

[telectrix]

total R =V/I, so you can then work out R2.

 

[jimmyray]

Hi pennychew, tried that, copying and pasting and also uploading a file of the jpeg, but no success! Can you get the gist from the description?

 

[pennychew]

Yeah i think so, ive just drawn it out and tried to post it but it wont work for me either!

 

[pennychew]

Yeah i think so, ive just drawn it out and tried to post it but it wont work for me either!

Scrap that, ive just reread your post and realised you said series and not parallel!!

 

[pennychew]

Just drew it out on paper as i couldnt be arsed to draw it all out on the computer again!!

The answers i get are...

A) 480v/5A = 96Ω
B) 120v/5A = 24Ω
C) 60Ω x 5A = 300v
D) 12Ω x 5A = 60v

 

[jimmyray]

Spot on mate! Didn't take you any time at all, nice one.

 

[pennychew]

I'll try and put the next question if it lets me post an image.

 

[Marvo]

I like it. You can never get too much Ohm's Law practice.

 

[pennychew]

I like it. You can never get too much Ohm's Law practice.

I've got the series circuits pretty much cracked i think, i need to work on the parallel stuff a bit more now.

Bought myself a clamp meter as well so ive took a couple of light switches off in the house and checked the current through the switch wire then done the power calculations and its always just about tallys with the lamps fitted on that circuit. Nice to see it work in a real world situation if you know what i mean!

 

[Marvo]

It's always good to see trainees inquisitive, you can learn more on your own if you've got the motivation than you'll ever learn in a classroom. Don't get me wrong, you need to be taught the basics but the difference between scraping by as a house basher or doing something exceptional is up to the individual.

We had a young lad/trainee on here about a year or more ago, he had his on website/blog where he'd put up photos and youtube clips of some of the dozens of experiments he'd done in his own shed or garage. I remember one where he'd rigged up a fluorescent tube and had used a filament lamp as a ballast in series with it something like this. He'd also converted his pedal cycle to be battery powered using some scrap motor he'd laid his hands on. The thing about the guy was you could see a mile away he was genuinely interested, motivated and inquisitive and he was going to go far.

So keep pulling things to pieces and keep asking questions.

 

[Silly Sausage]

So keep pulling things to pieces and keep asking questions.

Haha...I spent my childhood pulling things apart, trouble was rebuilding them!
Not much change several decades later!!! :smilielol5:

 

[pennychew]

It's always good to see trainees inquisitive, you can learn more on your own if you've got the motivation than you'll ever learn in a classroom. Don't get me wrong, you need to be taught the basics but the difference between scraping by as a house basher or doing something exceptional is up to the individual.

We had a young lad/trainee on here about a year or more ago, he had his on website/blog where he'd put up photos and youtube clips of some of the dozens of experiments he'd done in his own shed or garage. I remember one where he'd rigged up a fluorescent tube and had used a filament lamp as a ballast in series with it something like this. He'd also converted his pedal cycle to be battery powered using some scrap motor he'd laid his hands on. The thing about the guy was you could see a mile away he was genuinely interested, motivated and inquisitive and he was going to go far.

So keep pulling things to pieces and keep asking questions.

Thanks for that Marvo, i'm probably of a similar mindset to that guy really, I've always enjoyed pulling things to bits and seeing how they work. I'm also quite fortunate to have a job where i can get some hands on experience with quite big highly automated machinery and sparkies on shift to quiz all the time! (also a canny stock of contactors, relays, photocells and switches and stuff to borrow for my test rig in the shed!)

Early days but we'll see how it goes!

Stu