# A few things for Physics MCQ to remember (points that people usually forget or don't know at all)

#### Doggybros

2 months ago I was struggling to pass in physics with a grade D.
Now I know everything!!!

#### thunderingthunder

welcome....but i not da lyfsaver type guy...cuz m not da geek type guy
Yeah,that I can understand by looking at your avatar

#### Doggybros

Hey, are you implying I'm a geek? Coz I'm absolutely not. Things that teachers say do not enter my head, but once I learn something by myself, I never forget it, and that's a handy ability to have, which has helped me in a levels.

#### fatima 007

Ok, just some things you dont normally find in books, or some things that will help you do your calculations without calculating anything.
People usually forget these things, and some dont know them at all
(Sorry the lambda symbol looks cranky, just couldnt find the real one)

In a closed pipe,
Wavelengths that fit in are all odd multiples of ƛ/4
For nth node, frequency is fn = (2n-1)f1 where n = 1,2,3,4 and so on....
where f1 is the frequency of the lowermost node ie ƛ/4 (See below if you dont understand nodes)

(If you don't know what a node is:
1st node is the one where ƛ/4 fits in.
2nd node is the one where 2ƛ/4 fits in.
3rd node is the one where 3ƛ/4 fits in. its different in open pipe, im giving the formula)

In an open pipe,
Wavelengths that fit in are all multiples of ƛ/2.
So there is ƛ/2, 2ƛ/2, 3ƛ/2, 4ƛ/2 and so on.

For nth node, frequency is: fn = nf1

(IMPORTANT!!!!)
Formula of phase difference: 2π/ƛ × x WHERE ƛ is the wavelength and x is the path difference.
In case you are super noob in physics go look up path difference, I'm not going into that.

Common wavelengths:
Gamma: 0.01 nm
X ray: 0.1 nm
UV ray: 30 nm
Visible: Violet: 400nm
Green: 500nm
Orange: 600 nm
Red: 700 nm
Infra red: 10 micrometers
Anything greater than 100 micrometers is radio wave

Symbol of a fuse is the one where the circuit wire goes through a rectangular box.
Symbol of a LDR is the one where two arrows are pointing to the box.
Symbol of a thermistor is the one where a line passes almost diagonally across a box and has a small extension at the bottom.
NOT TO BE CONFUSED with symbol of a variable resistor, an arrow passing almost diagonally through a box.

When there is no current, electrons move about randomly and when there is current, electrons move from negative terminal to positive.

For a case where two resistors are in series (usually potentiometer):
When resistance of one decreases, Voltage across it decreases and the voltage across the another increases.
Vice versa for increase in resistance.
(You can calculate in the exam but remembering this line helps you save some valuable time)

In a parallel circuit, Voltage across resistors is constant, so more resistance means less current, to maintain equal voltage.
In a series circuit, current across resistors is constant, so more resistance means more voltage.

pd is always less than emf because energy is needed to drive charge through cell.

When reaching terminal velocity, air resistance increases to a constant value.

For nuclear physics:
Diameter of an atom is in the order 10^-10
Diameter of a nucleus is in the order 10^-15

A question similar to this has been asked many times:
When same voltage is applied to each of the following nuclei, which reaches the highest velocity?

For this question, find the ratio of charge to mass. It is directly proportional to velocity and you can equate it to velocity for your convenience in the exams.

REMEMBER THESE POINTS AND I'M SURE I WILL HAVE HELPED YOU WITH 5-10 MARKS.
THAT'S ALL FOLKS!!!!
Hope I rang a bell in your head or at least told you something you didn't know.
DONT MOCK ME IF NONE OF THIS HELPED.
NOTHING WRITTEN ABOVE IS WRONG, I CAN VERIFY THAT.
Can you please explain the wire thing properly. the formulas are confusing. what's f1?

#### johnsth

Yeah,that I can understand by looking at your avatar
....i guess dat makes u da nerd gal

#### johnsth

Hey, are you implying I'm a geek? Coz I'm absolutely not. Things that teachers say do not enter my head, but once I learn something by myself, I never forget it, and that's a handy ability to have, which has helped me in a levels.
no dude....i was just sayin it......wasn't referrin 2 u

#### johnsth

lol eh?luks lyk u r one....btw....it says This member limits who may view their full profile.?do u?

#### thunderingthunder

lol eh?luks lyk u r one....btw....it says This member limits who may view their full profile.?do u?
Yes,i do...

#### johnsth

Yes,i do...
okkk.....................................................

#### Soldier313

Hey people, does anybody have a list of all the formulas we need for physics tomorrow..?