OCR Physics Unit 2 - G482 - (June Exams Preparation)

What kind of youtube videos? Our crap teacher made us watch ten minutes of a car chase from a terminator movie and then said "see, that was all about stopping distances" and then told us to read about it in the textbook. For a whole lesson. :unimpressed:

What do you mean you're unsure what to do? I've started reading revision books and looking stuff up online and I already feel like it's helping me to understand better. 10 weeks til exams, still plenty of time to learn it if we start now and work hard!

Random Youtube Videos on Waves. It got to one point where he played a video that used advanced trig calculus to be able to prove what a wave does mathematically, stuff that doesn't need to be taught at this level. Infact, he showed all of that but taught us nothing we actually need for exam questions.

Your teacher is crazier than mine.

I've made notes on everything in the syllabus, but I don't yet fully understand it and now I'm going to do a ton of worksheet to apply theory to questions to be able to understand the concepts better.

Are you going to retake G481? I need a serious plan to understand everything inside out for June -_-

Reply 41

brawlerpit

1

Original post by Boy_wonder_95

The wording isn't bad in the exam trust me, each G482 paper follows the same structure, it starts off easy with Electricity stuff (simple calculations and sketching circuits), then it gets a bit challenging with all the complex wave theory, and then lastly you get a bit of Quantum at the end which is really nice and if you're lucky you may even get a little mini-essay on Quantum theory :biggrin:

. It's just that the exam is really long and tiring I almost wanted to just give up on this exam in Jan :tongue:

, but I'm glad I didn't as I ended up with a good mark (146/150). And another thing is the grade boundaries for G482 are relatively low compared to G481 which I'm taking in June.

Still looks like there is a lot of content to cram into your head. Thanks for your advice though, its really helpful! I will probably do the specimen paper once I cover everything and understand it to see how they are.

How is the timing for marks in the exam? Are you rushed for time?

Reply 42

sessess

Original post by brawlerpit

Random Youtube Videos on Waves. It got to one point where he played a video that used advanced trig calculus to be able to prove what a wave does mathematically, stuff that doesn't need to be taught at this level. Infact, he showed all of that but taught us nothing we actually need for exam questions.

Your teacher is crazier than mine.

I've made notes on everything in the syllabus, but I don't yet fully understand it and now I'm going to do a ton of worksheet to apply theory to questions to be able to understand the concepts better.

Are you going to retake G481? I need a serious plan to understand everything inside out for June -_-

I'm retaking G481 but haven't decided just yet whether to do it this June or next year. Next year would be easier as we're doing M1 in maths and the courses cross over a little, BUT next year there's no January exams so I'll have all my unit 4 and 5 exams and any unit 2 retakes to worry about so I don't want to have too much pressure, you know?

I'm already making chemistry revision notes to memorise definitions and reaction mechanisms, I think I'll start doing the same for both units of physics this week.

Reply 43

Boy_wonder_95

15

Original post by brawlerpit

Still looks like there is a lot of content to cram into your head. Thanks for your advice though, its really helpful! I will probably do the specimen paper once I cover everything and understand it to see how they are.

How is the timing for marks in the exam? Are you rushed for time?

Yep that bit's true and the annoying thing is you'll only be tested on 50% on the content :rolleyes:

yet you have to revise all 100% just in case... It takes long to learn aswell, it took my class from September to just before the Christmas breaks to learn it giving us just one month to revise :redface:

The timing's pretty fine tbh, it depends how confident you are with your maths and handling equations, it takes me roughly an hour to do this paper using the rest of the time to check

What's G481 like?

(edited 11 years ago)

Reply 44

Boy_wonder_95

15

Original post by Law-Hopeful

I'm currently struggling with polarisation, can anyone help explain to me what it is basically, how it works, why it works, and what we need to know about for the exam, it'd be hugely appreciated!

I understand that it blocks off some waves if they are at a certain angle, but I don't really understand it.

Thanks!

Refer to Post 12.

Reply 45

brawlerpit

1

Original post by Boy_wonder_95

Yep that bit's true and the annoying thing is you'll only be tested on 50% on the content :rolleyes:

yet you have to revise all 100% just in case... It takes long to learn aswell, it took my class from September to just before the Christmas breaks to learn it giving us just one month to revise :redface:

The timing's pretty fine tbh, it depends how confident you are with your maths and handling equations, it takes me roughly an one to do this paper using the rest of the time to check

What's G481 like?

I think if you do G482 before G841 you won't find it that hard. G841 is pretty much how you are describing G482 with less content.

In my opinion, the paper is usually half written definitions and half maths problems. To me, I found the maths easier than the definitions/concepts the book explained. I found was that the exams asked you questions on theories that weren't explained in the texts books so I would say you need research them or remember them from the markscheme.

The Jan 2013 was mostly worded questions which tested your theory.

But I got a C, people on here got 100% - so you should be asking them :P

Reply 46

Shinusuke_Akki

OP

1

PART 2/5
RESISTANCE

The Electromotive Force (e.m.f.) of an energy supply is amount of electrical energy transferred per unit charge when transformed from another type (e.g. battery - chemical to electrical).

V= W/Q (Electromotive force = electrical energy transferred / charge)

e.g. a 1.5V converts chemical energy to electrical energy, it converts 1.5J of energy per Coulomb (1.5JC^-1). If an electrical device requires an e.m.f. of 6V a battery containing four 1.5V cells could be used.

Potential Difference (p.d.) is the amount of electrical energy transferred per unit of charge in to another form. It relates to the electrical energy being converted to another form when passing through an electrical component (e.g. LED - electrical energy to light).

Potential Difference is measured using a voltmeter, which must be connected in parallel as it is testing the energy change over the component; an ideal voltmeter would have infinite resistance as the voltmeter mustn't affect the current flowing through the component.

Volts - Electromotive Force and Potential Difference are both measured in volts(V) - 1V means an energy of 1J is transferred per Coulomb. 1V=1JC-1

Ohm's Law states that the current through a conductor is proportional to the potential difference across it, provided physical conditions (e.g. temperature) remain constant.
Resistance is defined by the equation of Ohm's Law V=IR

I-V Characteristics of Electrical Components

Copper Wire
The I-V characteristics graph of a piece of wire shows that the current flowing through it is proportional to the potential difference.
https://twitter.com/shinusuke_akki/status/311257972774952960/photo/1

Filament Lamp
https://twitter.com/shinusuke_akki/status/311258401571237888/photo/1

LEDs
https://twitter.com/shinusuke_akki/status/311258821362323456/photo/1
LEDs switch on instantly, operate at low p.d.s (use little voltage), have a long working life, are very versatile and robust; due to these reasons are often chosen over filament bulbs.

Resistivity
The resistivity of an object (measured in Ωm) depends on it's material and varies with it's dimensions; It is proportional to it's length and inversely proportional to it's cross-sectional area.
The resistivity (ρ) of a wire:
(length, l; cross-sectional area, A; resistance, R)
ρ=(RA)/l

Temperatures Affect on Resistance
In Metals as temperature increases so does the kinetic energy of it's atoms, this reduces electron velocity and hence resistance has increased.

In a Semiconductor e.g. an NTC (Negative Temperature Coefficient) thermistor, resistance decreases with temperature.

NTC Thermistors are used to prevent surges in electrical circuits; when the circuit is first turned in and there is a 'surge' in current the thermistor (which is at a low temperature) limits the current, preventing the surge from damaging any components; the current increases the temperature of the NTC thermistor which in turn allows more current to flow, now at a safe level.

NTC Thermistors are also used to measure temperature, as the temperature increases and the resistivity increases, the current also increases. An ammetre is connected to the circuit to show the change in current, it can be calibrated to reflect temperature.

Electrical Power
Power is the rate of energy transfer (the rate at which electrical work is done).
P=W/t or P=IV
Since V=IR, when subbed into P=IV:
P=I2V
Since I=V/R, when subbed into P=IV:
P=V2/R

Watts - Power is measured in watts. 1W=1Js-1.

Domestic Electrical Supply
Domestic electrical supply is delivered at a 60A current, with a 230V e.m.f.

The incoming domestic electrical supply is connected to a distribution board which is connected to a number of ring mains, each with its own fuse or circuit breaker. The number of ring mains connected is dependent on the power maximum current. All appliances directly connected to the ring main and the sockets are connected in parallel.

A Fuse is a component with a thin wire running through it, if the current is too high, the wire melts, preventing the circuit and its components from being damaged (except for the fuse which is cheap and easy to replace).

Electrical Energy (W=Pt) is measured in either joules or kilowatt-hours; it is sold by electrical companies in kilowatt hours. 1kWh is the supply of 1kW every second for 1 hour.
Gas companies also sell gas in kWh and is cheaper as electrical companies loose most of their input energy in the conversion to the electrical energy they sell.

THE END OF PART 2/5

Reply 47

motivatedshroom

2

Please can anyone explain how I find the total resistance of this circuit?

(edited 11 years ago)

Reply 48

motivatedshroom

2

Also, there's a question:

You're given three resistors of 3 ohms. How would you arrange them to get 4.5ohms total R?

3+1.5=4.5

How'd you get1.5?

Posted from TSR Mobile

Reply 51

Gotzz

13

Original post by motivatedshroom

Please can anyone explain how I find the total resistance of this circuit?

Do the series part first, so 2+2+2=6 kΩ
Then that is in parallel with the other one so you do 1/2 + 1/6 = 2/3
So to get R you do 3/2 = 1.5 kΩ

Reply 52

Gotzz

13

Original post by motivatedshroom

Also, there's a question:

You're given three resistors of 3 ohms. How would you arrange them to get 4.5ohms total R?

Put 2 in parallel; 1/3 + 1/3 = 2/3 therefore R=3/2=1.5Ω
Then the 3rd one in series so 1.5 + 3 = 4.5Ω

Reply 53

Joseph-

how is everybody making notes for this?

i am using the book they gave us in school, making hand written notes, what about everybody else?

Reply 54

Joseph-

my school chose to do g481 in the summer along with this,

are the papers similar to each other? or do they ask very different questions every year? and how hard was the one this january? any tips would be appreciated

Reply 55

Boy_wonder_95

15

Original post by Joseph-

my school chose to do g481 in the summer along with this,

are the papers similar to each other? or do they ask very different questions every year? and how hard was the one this january? any tips would be appreciated