Test question

Noah wrote: Some of those practice test questions are, well... questionable.

That's the least you can say. I'd call them a pain in the butt :sick:

Dylan wrote: That's the least you can say. I'd call them a pain in the butt :sick:

Yeah, some of those questions are NOT very well written. And that's not just me being sore about getting that question wrong. :lol:

The actual test questions are much better written. This means that, after studying with the frustrating Motor Age questions, the test seems easy. :silly:

Tyler wrote:

Dylan wrote: That's the least you can say. I'd call them a pain in the butt :sick:

Yeah, some of those questions are NOT very well written. And that's not just me being sore about getting that question wrong. :lol:

The actual test questions are much better written. This means that, after studying with the frustrating Motor Age questions, the test seems easy. :silly:

:lol: :lol: Well hadn't thought of it that way... Is Motor Age the only one with test questions? Just wondering..

Tyler wrote:

Dylan wrote: That's the least you can say. I'd call them a pain in the butt :sick:

Yeah, some of those questions are NOT very well written. And that's not just me being sore about getting that question wrong. :lol:

The actual test questions are much better written. This means that, after studying with the frustrating Motor Age questions, the test seems easy. :silly:

Seriously! I was stressing after grappling with the test questions, but ended up with perfect scores in the end!

Dylan wrote: Is Motor Age the only one with test questions? Just wondering..

Thankfully, no! :lol: There's other test prep material publishers out there with practice questions, like Delmar . Though, these seem to be just as frustrating at times. That A9 book had a ton of questions diagnosing no starts, but the actual test barely even asked.

There's also practice questions you can buy from ASE directly, but it's kinda expensive.

Ok here's another one, saw it on FB .... Just thought I'd share it here

In the diagram below which bulb(s) glows brightest and why?

10W, 100W, 500W, equally....

Ummmmm, the 10W? :dry: :huh: I have no idea at all. :lol:

I will go with Tyler on this one, the 10w will be the brightest. The why would be it has the most resistance and the other two would have less current flow. (crosses fingers)

Thx for answering guys and of course you are correct

The 10W has the highest resistance and so it will have the biggest voltagedrop and shine brightest. Current is the same in the whole circuit since it's in series. Some ohm's law will tell us that. When I saw this on FB I scratched my head at first :blush:

Dylan wrote: Thx for answering guys and of course you are correct

Psh, I knew it all along. :lol: :silly:

Tyler wrote:

Dylan wrote: Thx for answering guys and of course you are correct

Psh, I knew it all along. :lol: :silly:

Of course you did

This is easy

Guys it's simple ok

Duty Cycle = Pulse Width / Total Period of the signal

so... the answer is B
because

if the period is 4 TIMES The Pulse Width
Hence if we represent the period as 100% as a ratio
it has to hold true that the PW = 1 Quarter of that
hence
100 / 4 = 25 %
DONE

FOR EVERYONE STILL SCRATCHING THEIR HEADS
and wondering... HOW DOES THAT WORK

Ok, LET'S DO THE MATH
BUT.. i Won't do it the whole way.
There's no point in me giving you the complete answer.
but i will make it easy

First of all, LET'S POINT OUT THE OBVIOUS MISTAKES that Technically make this impossible to solve without certain Assumptions

1. We do not know the polarity of the Voltage Source
Meaning we don't known if it's AC or DC

2. We do not know the direction of the current
Meaning we don't know if we are using ELECTRON FLOW THEORY or CONVENTIONAL CURRENT FLOW THEORY

3. also since we don't know the direction of the current.
WHY ARE YOU ALL ASSUMING THAT IT'S RUNNING TO THE SWITCH FIRST.
Why can't you assume that it's running to the 500 W Globe first and therefore
the answer is the 500 Watt Globe (Technically , based on the lack of detail in the diagram
you cannot disprove this answer) but, it is Facebook.. so.. yeah.. ok
Let's just assume that it does go to the Switch first

4. We are not given the resistance of the switch

5. We do not know the resistance of the wire itself

SO LET'S MAKE THESE ASSUMPTIONS so no one has a heart attack

we are dealing with a 120 V DC (Direct Current) Voltage Source

We are using CONVENTIONAL FLOW THEORY (meaning, we are going from a High Energy level to a Low Energy Level) because it's easier to understand

We are making the assumption that the wire from Source to Switch is Positive (+)

We will assume that the switch has 0 ohms Resistance

We will assume that the wire has 0 Ohms Resistance

OK

THIS IS WHAT WE KNOW

We have 120 V DC
we have 4 Globes 10 Watt 100 Watt 500 Watt

Now,
STEP 1. Identify the circuit as Series or Parallel
ANSWER : this is a Series Circuit, because there is only 1 path that the globes / Resistors are located on
and there are no Nodes in the Circuit

GUYS, from here on i'm going to call the LIGHT BULBS "Resistors" OK
because Electrically speaking, they are
they provide Resistance to the circuit

so when you deal with Series Circuits

- EACH Component in series has the MAXIMUM Current Running through it and the circuit
- EACH Componen will have a REDUCED VOLTAGE

Meaning
the series Circuit starts with 120 Volts
we assume no resistance in the switch
we assume the switch is in the CLOSED CIRCUIT POSITION
as the Current Enters the First Resistor, Voltage is 120 V DC
as the Current Leaves the First Resistor there will be less Voltage

if we call the first resistsor (R1) and the second Resistor (R2) and the last one (R3)
we can apply this formula to calculate the voltage coming back to the Source
let's call the Voltage Back to Source (VS)
and let's call the SOURCE (S)
so....
VS = S - R1-R2-R3
or you could say

VS = S - (R1+R2+R3)

THIS IS CALLED SIMPLIFYING A CIRCUIT
if you have 3 Resistors in Series
you can add the sum of the resistors to create what is called an "Equivalent Resistance"
(ER)
so by the same token you can add up the total wattage in a series circuit to create EQUIVALENT WATTAGE
(EQ)

hence we can say that we have EQ = 10+100+500
hence EQ = 610 Watts

Now we are getting somewhere

we have
120 Volts DC
610 Watts

so if we have 2 Values , we can solve for the third

SINCE CURRENT IS CONSTANT THROUGH A SERIES CIRCUIT
let's find the current

The formula according to Ohm's law is

Watts = Volts x Amps
W = VA
or
W = V x A

but we want amps

so it's
Amps = Watts / Amps
Amps = 610 / 120
Amps = 5.083 Amps

another way to do this is like this

there is formula for Power
Power is measured in Watts

hence P = VI (this will be the first thing you'll learn in an electronics engineering course, Week 1)

so.
Power = Voltage x Current
Power is Measured in Watts
Voltage is Measure in Volts
Current is measured in Amperes

so
P = V x I

but we want to solve for I
so we flip it

I = P / V
I = 610 / 120
I = 5.083 Amps

NOW.. FOR THOSE OF YOU WHO ARE SAYING
Why is it not

I = V / P

because in school when we do this

5 x 4 = 20
we can do this in reverse

20 / 4 = 5

OHMS LAW DOESN'T WORK LIKE THAT... that's the answer

Ohms law is a set of rules,
and You cannot flip them any way you want, UNLIKE IN MATHS

the way they are is the way they are
that's why

I = 5.083 Amps

Now that you know that you can

a) combine Resistors in Series to form Equivalent Resistors
b) Combine Wattage in Series to form Equivalent Wattage
c) You know the voltage is 120 V DV
d) you know the Curent is 5.083 Amperes

if you wanted to find TOTAL RESISTANCE IN THE CIRCUIT
you would use Ohms law as follows

R = Voltage / Current

R = V/C
hence

R = 120 / 5.83
R = 23.60 Ohms

now you also know the EQUIVALENT RESISTANCE


NOW WORK THIS PART OUT FOR YOURSELF

CALCULATE THE VOLTAGE DROP ACROSS EACH RESISTOR

now let me give you an example

+

---

> -
SOURCE

---

R1

---

R2

---

BACK TO SOURCE

Source = 12 V DC
R1 Volt Drop = 5 Volts
R2 Volt Drop = 7 Volts
Current = 2 Amps

find the resistance of each Resistor

Now also LAW OF CONSERVATION OF ENERGY
energy cannot be created or Destroyed
ENERGY IN = ENERGY OUT

KIRCHOFFS LAWS

ANSWER
which means

if you start with 12 V DC
then the first resistor sucks up 5 Volts
you will measure with your multimeter from one side of R1 to the other 5 V
but if you measure from the output of R1 to the input of R2
you will get 12 - 5 = 7 V DC
and therefore if you measure across R2 you will also get 7 V DC and from the output of R2
to the negative terminal on the source, YOU WILL GET 0 V

ENERGY HAS BEEN CONSERVED

now use Ohms law to calculate RESISTANCE in my example

Resistance = Current x Voltage
R = IV
or
R = I x V


NOW THE HARD PART
go back to the facebook thing

we've worked out
Voltage 120 V DC
we've work out the current - 5.083 AMPS

we know the EQUIVALENT WATTAGE is 610 Watts
we know the individual wattage of each globe OBVIOUSLY

and we know the EQUIVALENT RESISTANCE

YOUR MISSION SHOULD YOU CHOOSE TO ACCEPT IT IS...

CALCULATE THE RESISTANCE VALUES OF EACH GLOBE


HINT : Calculate the Ratios between Them

Use 610 Watts to express 100% of the total Wattage
find the ratio
then

Get your EQUIVALENT RESISTANCE OF 23.60 Ohms
and apply the ratios to get the exact value of each Resistor / Globe

then work out the volt drop across each
and YOU WILL THEN TRULY KNOW WHICH ONE IS BURNING THE BRIGHTEST


GOOD LUCK

Knowledge is our reward sir LOL

MartinKuliza wrote: Knowledge is our reward sir LOL

Let me guess, you like math?

Great explanation in detail. Cool!

Attention : Dylan
RE Your reply :

Let me guess, you like math?

Great explanation in detail. Cool!


My Response:
LOL, [SARCASM ] What gave it away ?? {Sarcasam]

but.. on a serious note though,
No.. probably not as much as you think,
but What i do like is this

1. Helping People that need help
2. Giving Clear and Complete Answers

I personally believe that if i give a part answer
a) it's inefficient
b) it ALWAYS results in more answers due to the fact that it was a non complete answer

The solution.. Answer the first question correctly and

a) You will either have no more questions to deal with
or
b) You will have far less to deal with
Either way it wins

beyond that
Paul said to me on a you tube channel that he wanted to invite me on this forum and that he had a lot of Beginner Mechanic students here.

I was happy to help, especially since i have a young bloke who is keen on
a) Electrical Engineering
b) Working on Engines as a Hobby

I'm not a mechanic by any means, I have never pulled engines apart, However i am an engineer.
I'm an Expert in I.T. , Telecommunications and Electrical and Electronics.

I do know certain things on cars, I'm not completely obvlivious, but, i will not stand here and say i'm a mechanic.

anyway, i figured i could
a) teach myself more about my own car from Paul's Teachings
b) teach my young bloke, PROPERLY how to understand Electrical Circuits and the Math behind the engineering, and How to use an Scope correctly and understand it
so.. this kid is around 17, and until he figures out if he will be an Electrician or Mechanic, i figure why not teach him, and learn for myself at the same time
and.. while i'm doing so, why not help a few others here as well.

my deal is... I'm passionate about what i love to do
Not so much about the math

Nice to meet you mate,
Be Cool

Quick question if i may, because paul has not yet answered.

Feel free to say NO, if you wish

i was thinking , instead of typing all this stuff, it might be easier if made a video or Video's in reply to certain questions and merely posted a link to a cloud (the Cloud being..... MEGA) it's safe

so, is it cool if i make videos personalized to the question (Assuming the question requires a lengthy answer)
or is that against the forum rules

look forward to the reply
thanks mate

I definitely appreciate the info and explanation sir! We're here to learn from each other. For some this will be new material whilst others get a refresh
Now about the videos, this is up to Paul. So I sent him an email.
Anyways great to have you here and don't hesitate to share the knowledge!

Martin
Thanks for joining the forum. I prefer not to have personal videos to answer peoples questions. You sent me a 1.5 hour video yesterday on my website with most of it being a misconception of what ScannerDanner Premium was. Don't get me wrong, I really appreciated your time, but that could have been cleared up in a few minutes.
My suggestion is to keep your answers short and to the point. That would be the most help we can ask for.
I hope you understand. Thank you again for your time!

Attention : Dylan

thanks mate

Re : The videos... Yeah, i have not put up any yet, because i have not got the go ahead from paul
i have however sent paul a personalized video.. asking the question, but i have not received an answer,
Not sure if he has viewed the video as yet.
Until he does, i won't post video answers. not to worry

RE Sharing the knowledge
dont' worry mate, i won't hesitate , but if anyone else is reading this.
i would ask them to understand this

1. I do understand that my answers at times can be lengthy (well, after all these are technical questions.. so . it's to be expected)
2. However, these answers are not for everyone, and i get that
3. I'm not made of glass

so.. if someone doesn't like the length of the answers or doesn't like me, i would LOVE FOR THEM TO TELL ME, and i won't take it personally. Guaranteed.
but i do want to know.
i will do my best to keep the answers as relevant and brief as possible, hence why i think videos are a better idea. hehe
and also i can pull out my scope in the video and multimeter and go over fundamentals of Electrical Engineering

but again, i need people to give me feedback, because if no one is going to read my answers, there is no point posting them
but..let's see how we go

i'm happy to teach the newbies if they are happy to learn
simple as that

thanks for welcoming me to this forum mate
be cool
feel free to ask anything

hi mate

yep, no problem
i'm not getting you wrong. so don't worry

the video was that long because i was under the understanding that you didn't understand scopes,
but after making the video, you cleared that up.. so.. yeah.. i could have save myself a shit load of time

all good though
i can now access the site obviously
and i'll leave you to fix those other issues on your end at your leisure

i was just waiting on the answer about the personalized videos
but as i said in the video.
if you say NO, i can certainly respect your decision on your site

so.. cool, no videos then.
thanks for responding
have a good one

PS : re the young bloke, i told him about your site, he's excited hehe
i'll be subscribing for a year after the trial period i would imagine
be cool mate