## How Mr. G stole your Holidays…

So, you’ve read the story about the Grinch stealing christmas – or you’ve seen the movie, or you’re looking up wikipedia to find out about it right now.

Well, I’m not going to let a cartoon story book character have all the fun, so here are the work that you must have completed by the start of week two. This means that you could choose to do no work through the holidays, and try and finish it all after you return to school…

Of course, I don’t recommend that strategy – it is better to spread it out through the holidays and ask for help when you need it. Post a comment on this post if you need help!

Check each of the subjects below to see what you must have finished by the above deadline!

Mathematical Methods Units 3 & 4

1. Read the posts on Circular Functions (1, 2)
2. Complete Book checks 1 – 3 (chapters 3, 4, 5)
3. Complete Maths Online Skill Revision Assignment (THIS IS A WORK REQUIREMENT!)
4. Complete all unfinished Maths Online (THIS IS A WORK REQUIREMENT!)
5. Complete last SAC re-do task
6. Print out the Book Check 4 (Chapter 6).

Physics Units 1 & 2

1. Complete Electricity Practical Report
2. Update your Lab record (it should include Circuit demo, Two CUPs (current & voltage), 3 Practicals (Ohm’s Law, Current Dividers and Voltage Dividers)
3. The circuit simulator is here.
4. Complete the explanatory sentences for each CUP (Current & Voltage worksheets) (1 sentence for each dial reading)
5. Complete Hewitt Worksheets (Radiation & Circuits)
6. Complete Questions in supplemental notes for radiation.
7. Notes for Electricity will be inserted here shortly. Read them!

Year Enrichment Mathematics

2. Checklist for chapters 1 & 2
3. Complete Mathematics Online Assignment.

Enjoy the rest of your holidays!

Explore posts in the same categories: Admin, Assessment, Mathematics, Physics

### 58 Comments on “How Mr. G stole your Holidays…”

1. Jack Says:

Question: Why is the gradient of an Ohmic device constant?

Although there is no true Ohmic device since it is relatively hard to keep a constant physical conditions such as temperature, the gradient of an ohmic device is always constant since it expresses a repetitive ratio between voltage and current.

In addition to this, the line on a graph is always linear, and when choosing two points on a linear graph, we can see that they both relatively have the same x to y ratio.

Eg, y = 2x. Point 1 ( 4, 8 ) Point 2 (6, 12). What we can see from this linear graph is that for the ratio between these two variables are 1:2.

By using these two points we can figure out the constant gradient Resistance by: V2 – V1/ I2 – I1.

http://www.a-levelphysicstutor.com/elect-concepts-units.php

2. Brendan Says:

Hi sir!

This will probably be really obvious to me and I’ve just gone blank, but what are the questions in the supplemental notes for radiation?

Thanks!

• CyberChalky Says:

In the notes that you received (from me, not the textbook), there were questions in grey boxes. Those ones are the ones I’m talking about.

3. Paktia Says:

My question was: What is a current divider?, ill try answer as best as I can.

Current dividers are the inverse of voltage dividers, voltage dividers work with series circuits, while current dividers remains constant. They work with parallel circuits as long as the voltage is the same across all components, and any series circuits must be combined before using the current divider equation

Current divider refers to splitting current between the branches of the divider.

4. Lovleen Says:

Hello,
my question was…
Why a curve line in V-I or I-V graph not a ohmic device?
I think it is because a curved line will show a definite increase or decrease in current. Which means there is a change in resistance.
and in a true ohmic device, the resistance remains a constant. Which means that the the device will never heat up. And as something heats up, it gains resistance.
This is why a curved line in a I-V or a V-I graph is not an ohmic device.
Hope it’s right… correct if wrong
thank you

• CyberChalky Says:

That’s pretty good, Lovleen. Could do with a little more detail on what you mean by a “True Ohmic Device”.

• Lovleen Says:

I’ll try my best to explain what i mean by a “true ohmic device”. By that i guess i mean, an actual ohmic device. In which the resistance will only change if there is a change in current or voltage. But the resistance increases as the circuit components heat up. And the only time when a new ohmic device is when it is placed be in 0 degrees Kelvin temperature.

• CyberChalky Says:

Lovleen, I think you really need to rethink your answer. Your statement “which the resistance will only change if there is a change in current or voltage” is confusing, and depending on what you meant by it, wrong. Start again – you need to frame your explanation more carefully.

• Lovleen Says:

Isn’t resistance a constant in an ohmic device. And whatever happens to the voltage happens to the current, and the resistance stays a constant ratio… i hope i’m not off topic and actually making sense.

• CyberChalky Says:

Lovleen,

Yes, resistance is a constant in a “true ohmic device”, but your previous statement said that “which the resistance will only change if there is a change in current or voltage”, implying that resistance could change. You need to restate what you mean in order to clarify your point.

• Lovleen Says:

Ahhhh, I see what I said wrong. But then how should I say it. Should I use ‘Total resistance of a circuit’ instead of just ‘resistance’. Would that make sense? And that video is always going to make me think again, thanks

• CyberChalky Says:

If a device is a “True Ohmic” device, then, regardless of voltage across it or current through it, the ratio of voltage to current (resistance) will always be the same. The resistance or total resistance of an ohmic circuit is *constant*. As you increase voltage, current will increase in proportion.

5. Brendan Says:

What does Ohms law state and why?

Ohms law is the formula R=V/I which states the relationship between current, potential energy (voltage) and resistance. It states that current and PE are directly proportional to each other. This proprtionality is resistance. When current and voltage are plotted on a graph resistance is equal to the gradient of the line formed because resistance in a circuit cannot change even if PE and current do.
Checkout page 42 of our physics book for some more info on ohms law and a picture/video will be here soon when i figure out how………

6. Zahidah Zain Says:

2x+10 degrees
How do I solve that? It’s a cylic quadrilateral.
It’s on one of the activities from Maths online and there’s no example.

7. Hayley Says:

Hey,
By the Mathematics Online assignment do you mean our maths online work? Or is there another assignment I didnt hear about?

Hayley

• CyberChalky Says:

Hi Hayley,

It’s just the maths online work! I could make up an assignment if you want one…

• Andrea Says:

haha no thanks sir. Could u email the maths online questions? I’ve done most of it on the holidays. But it’s difficult to continue it, since when I do get internet, which is rare, I forget my user name and password.

8. darrren10 Says:

darrren10 Says:

March 30, 2011 at 3:12 PM
Cool, so my question was, why does a V-I graph have to start from the origin. So as stated by Ohm’s law, the current to voltage ratio has to be the same. On the y-axis, where y is 0, the x value has to be 0 as well. If it started somewhere eles, then x would not equate to y and therefore would not be ohmic.

and here’s an informative video, kinda neatly puts ohms’s law, voltage and current up nicely together

9. Zahidah Zain Says:

Sir, I really need help, I’ve tried everything…
I’m trying to complete the second task on gradients. I’ve completed all of them except this one; 5y=2x+30
How do I get y by itself so I can find the y-intercept?
I know the formula is y=mx+c, but I can’t solve this one…

I know how to solve the longer ones (e.g. 3x-2y+8=0), but I get confused when doing the shorter ones.

• CyberChalky Says:

Hi Zahidah,

Here is how to do it
5y = 2x +30 (starting equation)
5y/5 = 2x/5 + 30/5 (dividing all terms by 5)
y = 2x/5 + 6 (simplified)

So the gradient is 2/5, and the y-int is (0,6).

Hope that helps!

• Samson Says:

sir why dosen’t HPSC teach the intercept/intercept methode for gradients?

• CyberChalky Says:

Hi Samson,

The intercept – intercept method is a a method that only works if you have the interecpts. Sometimes finding the intercepts can require additional steps – the gradient formula:

m = (y2- y1)/ (x2 – x1)

Works on any pair of points, not just the intercepts.

10. darrren10 Says:

Hey Mr. G,
in circuits, if the switch is not closed, there’s current AND voltage yea? but if the switch is not closed, there’s voltage but no current? and if so, is there only voltage as far as it can be from the power source to the end of the switch?

• CyberChalky Says:

Hi Darren,

By not closed, I presume you mean open.
If the switch is closed, current can flow, and there is no potential difference between the terminals of the switch.
If the switch is open, current cannot flow, and there is potential difference between the terminal of the switch.

• darrren10 Says:

so when the switch is open, there would be potential difference at points up to the end of the switch and the points on the other side of the switch?

• CyberChalky Says:

Think about what you are asking in terms of the M&M example (the handing over/passing version, where instead of moving, each person passes the M&M to the next person in line).
At the switch, they cannot pass M&Ms across gap. Beyond the gap, the M&M can still be passed along. This means, that before the switch, there will be M&Ms, and after the switch there will be none. This is a difference in number of M&Ms per person – otherwise know as Voltage or potential difference.

11. Tia Clothier Says:

Hey sir, I was hoping you could post the checklist for Year 10 Enrichment Maths when you get the chance. I’m up to date with everything else, and I’d like to get a head start with the book work..
Thanks.

12. Manar Sarweh Says:

Hey sir, Thanks for the checklist for chapters 1 and 2!

• CyberChalky Says:

Sure, anytime you want more work in your holidays, I’m glad to oblige!
I do notice, however, that you’ve not finished your MathsOnline yet…

13. darrren10 Says:

Hey Mr G. another question.
So for the voltage sheet. there’s a circuit with a switch, a cell and a light globe. when the switch is open, i know that there is voltage until the gap,and afterwards there’s nothing. how would you mark the potential difference between both ends of the cell on a voltmeter. how do you know where to put the arrow?

14. Milica Says:

hey sir,
when is the checklist due??
and can you do a revision class on negative and positive numbers and tan??
thankss,
Milica

• CyberChalky Says:

Hi Milica,

I’ll do some revision about negative & positive numbers. We’ll wait for the next unit before I revise trigonometric ratios (including tan).

The due date for the chapter 1 & 2 will be about week 5.

See you soon!

15. Zahidah Zain Says:

Hi Sir,
I’m doing my Maths online now and I’m really stuck on The Point Gradient Formula activity.
It says : y-y1=m(x-x1) , where m is the gradient.
Well.. I understand all that, but when I try and solve it, I never get the correct answer.

For example: Find the equation of the line passing through (2,3) with the gradient 3.

Im stuck
and I really want to get all my Maths Online work done, before my house gets renovated soon.

• Zahidah Zain Says:

Dont worry sir, I got help from my tutor teacher.
I understand it now

• CyberChalky Says:

That was quick!

• Zahidah Zain Says:

Haha, i tried everything until it worked. However, I’m still quite confused about negative and positives.

Oh yeah, I just want to add in…..

I FINALLY FINISHED MY MATHS ONLINE 😀
I feel happy and completed 🙂

16. Paolo Says:

Hello Sir,

“Why any device on an IV graph is not linear?”

A device in an IV graph is not linear because no device can stay the same temperature. Temperature has a large influence on the constant resistance of the device. When a device heats up due to electrical flow this would result in more resistance. As you’re previous in class example explained that if you had to move between two rows of still rugby players that would be much easier than trying to pass them while they were moving. The only forms of true ohmic devices are theoretical, as the resistance will always be constant, and will be linear when displayed on an IV graph.

http://schools.wikia.com/wiki/Ohm%27s_Law
“Non-ohmic Conductors”

thats the source i used, it seems pretty legit for a wiki and uses undertstandable language

17. darrren10 Says:

Hey Mr G, did we ever cover the internal resistance of a source of emf in class?

Hey Sir,

The reason why I’m behind on Maths Online is mainly due to a ridiculous *easy* question which has taken me a while to figure out, but after using various strategies and method’s, I have been able to solve it with competence not only that question but a portion of that topic!

The question was find x: 2x+10 degrees and 3x+20 degrees.

In order to demonstrate my competence, I have written the question and the *easy* method to solving it!

(2x+10)+(3x+20) = 180

2x+3x+10+20 = 180 Add them together

5x+30 = 180 Which will you will get!

5x = 180-30 Subtract 30 from 180

5x = 150 Which will you will get!

x = 150/5 Divide 150 by 5

x = 30 So, x = 30 degrees

😀

I will hopefully finish my maths on-line by the end of tomorrow.

So thank you for being patient and sorry because I’ve not finished it on time!

19. darrren10 Says:

Hey Mr. G, my group was doing ohm’s law for the experiment and we were wondering what is the actual aim. I wrote “to observe how voltage and current at certain points change as the current supplied is changed” is that correct? if not what is the actual aim?

20. mitch Says:

Describe the hall way circuit? the circuit consist of two 3 pole switches a twin activ to connect the switches a power source and a load normally the light globe, it works by using the twin active an the 3 poles switches it makes a gateway between the circuit flipping one switch on will turn it on by connecting the circuit and when you turn the other switch off it switches to the other active disconnecting the circuit will upload picture when I’m not on my phone well diagram.

21. Levy Says:

Why don’t true ohmic devices exist?
Answer: Because when they get hot, they increase the resistance.

22. Hao Says:

Hi Mr. G,
Is it possible for you to post up the next blog post prior to tomorrow evening?

23. Rares Says:

Hei people, I love posting of my iPod! 😀
Alright, my question was why an ohmic device can’t have a negative gradient. It’s pretty simple if we had a voltage/current graph with a negative gradient then that means that if you increase voltage you decrease current. And the laws of physics say that if you increase voltage you increase current. Unless they changed or are wrong. And apparently physics is wrong so who knows! Alright peeps peace out

• Paktia Says:

Like a sombodeeeeeee, was doing a question and it asked for this. Nice post and well answered 🙂

24. Manar Says:

Hey sir, just wanting to know when you will be putting up your story on the blog so that partners can chose pages?

25. Renata Says:

Hey sir,
I was just wondering with the vels thing, what can i do for the thinking section and surd section to increase my vels?
I have started doing the ellipse things that you said to do, so will that also cover the thinking section or not?