i think its just an example to say because the current is passing through a resistence of 10 ohms every resistor , if you take two points between the two branches , you will get 0v measured
for question 20 at 22:10 why do you add the voltages together instead of subtracting them since its asking for the potential difference i would assume you have to subtract them?
with percentage uncertainties if it says to square it just means add it twice so for example 3 squared in percentage uncertainty means 3+3 so 4 squared means 4+4 which equals to 8 for percentage uncertainties you always just add even if it looks like you're meant to divide or square etc . I hope that makes sense sorry Im a student too so my explanation may not be that good
electricty is byfar hardest topic for me, and the ms for aqa realy doesnt help. but this video cleared my superstition and i feel more conifdent now thankyou
Hi again Science shorts, I just wanted to ask: - For a question such as 21 (with a P-i graph), would you be expected to know the graph shapes or always work them out based on what knowledge you have? - And also, Is Science Chinos your arch nemesis? Thanks
You just need to know that voltmeters have infinitely high resistance (and ammeters have near enough 0 resistance). And because the voltmeter is effectively in series now the switch is open, the very high resistance means that no current can then flow through it.
And if you can't remember that just think ammeters are always in series so must have 0 resistance (or no charge could ever flow through the circuit) and voltmeters are (meant to be) in parallel, so must have infinite resistance so that no charge flows through the branch the voltmeter is on (all goes through the component(s) it is measuring)
I know this video is old but I'm confused by question 16 (17:00). Wouldn't the resistor at the bottom also be in parallel? Why can you just add it onto 3/r?
It's not in parallel. If you look at the battery, when you go from positive end to the negative end, you have to go through that bottom resistor. It's in series because it forms a closed loop with every battery. Tbh it's kind of hard to explain but it just is, if you can't wrap your head around it do practice questions until you understand it intuitively.
I noticed in the video that the answer to question 33 was stated as A (current in A1 decreases, A2 unchanged). However, current splits inversely to the resistance of the branches. If the thermistor’s resistance increases, less current would flow through its branch, and more current would flow through the branch with the fixed resistor. This means A2 should increase, making the correct answer B. Could you clarify this?
You assume total current stays constant, which it does not, which is a common mistake. That's why you only consider how the pd of each branch changes - you never try and figure out what's happening to current first.
@@ScienceShorts But if total current is not constant, wouldn't the value in A2 not change no matter what? The p.d. across the 2nd branch changes right because it is our terminal p.d. and this is affected by external resistance which has changed?
You are arguing against yourself, tantamount to: "the total current will change, but a lower current in the top branch means a higher current in the bottom branch (which requires assuming that total current is constant)." There are a few ways of explaining it: - Every branch acts independently, as the p.d. stays constant. - V=IR is true for the bottom branch. If V and R don't change, neither does I for a component. - V=IR is also true for the top branch. As V is constant but R goes up, I goes down. - V=IR is also true for the whole circuit. As V is the same but total R has increased, total I has gone down, to account for the smaller current now flowing through the top branch. There is no reason why this should affect the bottom branch.
4:38 Q5 the answer should be B, no? A=pi×radius² not diameter. you need to half the 4.0%, you would then get an answer of 9.5% overall. 13.5% must be a throw off answer for those who don't half the 4.0%.
@@ScienceShorts hi for Q21 im a bit confused on what you're saying. "to increase I you need to increase V" like it makes logical sense in my head but I don't understand why you discount P=IV. in an exam i would automatically go to P=IV and get stuck lol. can you explain a little further? i think i understand why u need a constant in there. is it possible to use P=IV & if yes how would you do that? im tired and off my meds sorry lol
do you think you'd be able to cover long aqa a level physics questions anytime soon? your vids are a big help!
He does full past papers mate so just look at questions by topic on those full past paper videos
@@anthonywilliams7777 its okay im in university now lol
what did u get
@@luddy20
@@luddy20 I'm not 😔
@@CartmanProductions681 push through bro A levels is the worst but it gets sm better from there
Thank you so much! This has been a massive helping understanding how to actually do these questions. I hope you keep making these.
14:53 why does it decrease by 2v?
idk either
i think its just an example to say because the current is passing through a resistence of 10 ohms every resistor , if you take two points between the two branches , you will get 0v measured
Hey just wanna tell you love ur vids really get to learn a lot never give up
6:31 nice comedic relief in the midst of a brain wrenching😂
Redo for myself:
q 14 14:19
q 15 15:51
q 19 20:22
q 33 35:24
q 34 36:02
19:45 all that for one mark is daylight robbery
Nice video, I like how you tell which topic covers that specific question.
some lovely explinations u saved my life i was about to drop alevel physics but after ur vidoes and explinations i changed my mind thank uuuuuuuuuuuu
Please could you start doing worked solutions for the actual questions too. These videos are really helpful so thank you
for question 20 at 22:10 why do you add the voltages together instead of subtracting them since its asking for the potential difference i would assume you have to subtract them?
total pd in series is added together- it’s asking for difference between P and the earth not between the two resistors
Q5. 4^2 is not 8, its 16, therefore the answer is 21.5?
with percentage uncertainties if it says to square it just means add it twice so for example 3 squared in percentage uncertainty means 3+3 so 4 squared means 4+4 which equals to 8 for percentage uncertainties you always just add
even if it looks like you're meant to divide or square etc . I hope that makes sense sorry Im a student too so my explanation may not be that good
Thanks.
electricty is byfar hardest topic for me, and the ms for aqa realy doesnt help. but this video cleared my superstition and i feel more conifdent now thankyou
Great video- was really helpful
Hi again Science shorts, I just wanted to ask:
- For a question such as 21 (with a P-i graph), would you be expected to know the graph shapes or always work them out based on what knowledge you have?
- And also, Is Science Chinos your arch nemesis?
Thanks
8:00 why is there no current. And how did u infer that the voltmeter has such high resistance?
You just need to know that voltmeters have infinitely high resistance (and ammeters have near enough 0 resistance). And because the voltmeter is effectively in series now the switch is open, the very high resistance means that no current can then flow through it.
And if you can't remember that just think ammeters are always in series so must have 0 resistance (or no charge could ever flow through the circuit) and voltmeters are (meant to be) in parallel, so must have infinite resistance so that no charge flows through the branch the voltmeter is on (all goes through the component(s) it is measuring)
@@samwilliams8317 You should become a teacher
great explanation
Thank you for going through these, cleared up a lot of misunderstandings.
I know this video is old but I'm confused by question 16 (17:00). Wouldn't the resistor at the bottom also be in parallel? Why can you just add it onto 3/r?
It's not in parallel. If you look at the battery, when you go from positive end to the negative end, you have to go through that bottom resistor. It's in series because it forms a closed loop with every battery. Tbh it's kind of hard to explain but it just is, if you can't wrap your head around it do practice questions until you understand it intuitively.
@@pedrofile9661 Oh I see now. Thanks, that makes a lot of sense.
Super helpful thanks!
I noticed in the video that the answer to question 33 was stated as A (current in A1 decreases, A2 unchanged). However, current splits inversely to the resistance of the branches. If the thermistor’s resistance increases, less current would flow through its branch, and more current would flow through the branch with the fixed resistor. This means A2 should increase, making the correct answer B. Could you clarify this?
You assume total current stays constant, which it does not, which is a common mistake.
That's why you only consider how the pd of each branch changes - you never try and figure out what's happening to current first.
@@ScienceShorts But if total current is not constant, wouldn't the value in A2 not change no matter what? The p.d. across the 2nd branch changes right because it is our terminal p.d. and this is affected by external resistance which has changed?
You are arguing against yourself, tantamount to:
"the total current will change, but a lower current in the top branch means a higher current in the bottom branch (which requires assuming that total current is constant)."
There are a few ways of explaining it:
- Every branch acts independently, as the p.d. stays constant.
- V=IR is true for the bottom branch. If V and R don't change, neither does I for a component.
- V=IR is also true for the top branch. As V is constant but R goes up, I goes down.
- V=IR is also true for the whole circuit. As V is the same but total R has increased, total I has gone down, to account for the smaller current now flowing through the top branch. There is no reason why this should affect the bottom branch.
4:38 Q5 the answer should be B, no?
A=pi×radius² not diameter. you need to half the 4.0%, you would then get an answer of 9.5% overall. 13.5% must be a throw off answer for those who don't half the 4.0%.
That's not how uncertainties work.
Uncertainty doesn't decrease just because you halve the value.
@@ScienceShorts hi for Q21 im a bit confused on what you're saying. "to increase I you need to increase V" like it makes logical sense in my head but I don't understand why you discount P=IV. in an exam i would automatically go to P=IV and get stuck lol. can you explain a little further? i think i understand why u need a constant in there. is it possible to use P=IV & if yes how would you do that? im tired and off my meds sorry lol
@@x4ol I'm obviously a bit late, but if the current is directly proportional to p.d. then wouldn't an increase in current cause an increase in p.d.?
huge help, keep it up.
u the man
7:13 how did you know that those two together make 20 ohms?
Two identical resistors in parallel = half one of them.
Use the equation to prove it to yourself!
q22 is a rollercoaster
fantastic thanks, day before paper 1
Hi for question 14 how do we know we are losing 2v every time?
Yh that’s what I’m confused about
PDF?plz
worked solutions for the questions pls
can someone please explain why v/3=2I at 19:49
V=IR and R = 2