HSC Physics Question Thread

[zoe_rammie]

Sorry, this is just a simple question,

But does a galvanometer measure EMF or Electric current?

(I know that EMF gives rise to electric current, but still...sometimes even the teenies details makes all the difference)
Thanks to whoever replies to this

[imtrying]

Would it be more correct to refer to ultrasound passing through tissue as being transmitted or as being refracted? My textbook seems to use them interchangeably.

[RuiAce]

Sorry, this is just a simple question,

But does a galvanometer measure EMF or Electric current?

(I know that EMF gives rise to electric current, but still...sometimes even the teenies details makes all the difference)
Thanks to whoever replies to this

Current

EMF (electromotive force) is equivalent to saying "Voltage" in the HSC

[jakesilove]

Sorry, this is just a simple question,

But does a galvanometer measure EMF or Electric current?

(I know that EMF gives rise to electric current, but still...sometimes even the teenies details makes all the difference)
Thanks to whoever replies to this

Hey! A galvanometer can be set up to measure both. Most commonly, I think it measures current, but it can be set up to measure voltage as well

Jake

[jakesilove]

Would it be more correct to refer to ultrasound passing through tissue as being transmitted or as being refracted? My textbook seems to use them interchangeably.

I would probably go with transmitted through tissue. Just seems more scientifically correct, because refracted implies some sort of 'outward' movement, which I guess is also correct... so yeah either, but I would suggest transmitted

[Albertenouttaten]

Hi, could someone please explain to me what a black body curve is and what the UV catastrophe is. Im really confused

[Cindy2k16]

Hi for 2007 Physics Q25 it says "A student claims that a DC generator is an 'electric motor in reverse'" Analyse this claim with reference to the structure and function of a simple DC generator and an electric motor"
I can only find the notes from the marking centre for the older papers and they don't give an indication of what the final verdict should be after comparing the structure and function- So I was just wondering what you're meant to end up deciding about the student's claim?
Thanks in advance

[Albertenouttaten]

Well typically when they ask you to refer to a statement, it requires to to analyse the key terms within the statement e.g. DC motor AC motor similiarities, differences, transformation of energy types, source of torque, etc. And then i believe you would end with whether the statement is correct or not e.g. Therefore the student's statements regarding DC generators being and DC electric motor in reverse would be considered correct. Then again, the question could you also asking you to prove the statement, e.g. again like before, analyse DC motor AC motor similiarities, differences, transformation of energy types, source of torque. And then support the statement, this is pretty much the same as saying whether the statemnet is correct or not. Typically tho, these types of questions would normally be worded "Evaluate the Accuracy of the statement", "Discuss the following statement", but yeah means sorta the same thing.

Hope this helps

[Goodwil]

Hi again. I have 2 more questions.
1. When using the right hand rule for electrons/cathode rays, is the finger that is used for current pointing in the same direction as electron flow, or the opposite direction? (eg if electrons are moving to the left, is the finger for current pointing to the left or the right?)
2. For projectile questions such as the one attached (ie projectiles on uneven ground) should we set acceleration to be positive or negative? And is ΔY the same or opposite sign?
Thanks

[RuiAce]

Hi again. I have 2 more questions.
1. When using the right hand rule for electrons/cathode rays, is the finger that is used for current pointing in the same direction as electron flow, or the opposite direction? (eg if electrons are moving to the left, is the finger for current pointing to the left or the right?)
2. For projectile questions such as the one attached (ie projectiles on uneven ground) should we set acceleration to be positive or negative? And is ΔY the same or opposite sign?
Thanks

If I recall for Q2, in the answers for that one they made acceleration positive.

But there's a twist. Note how they also made Δy positive. Note that normally we would actually treat Δy as negative. This is cause overall, the particle fell downwards, in the vertical component sense.

Because they made Δy positive, they had to compensate by making a_y positive. Here, I would've made a_y (gravity) negative anyway, which would mean that Δy was also -150

[bethjomay]

Hey there, could someone help me with the calculations involved in each of these questions? Both from the 2014 paper, I feel sorry for Jamon and Jake now!

[jakesilove]

Hey there, could someone help me with the calculations involved in each of these questions? Both from the 2014 paper, I feel sorry for Jamon and Jake now!

Hey! Such a weird question, hey? It was from my paper, so I know it well You just need to make sure that the horizontal displacement of Ball Q stays consistent (ie 3 blocks). Then, you know that acceleration due to gravity adds a consistent amount of velocity per second. It starts by 'moving down' 3 blocks, and then 9 blocks, which means each second ADDS 6 blocks worth of down. So, the next vertical position should be 9+6=15 blocks further down! Absolutely stupid question, but it does make you think about the actual physics behind projectile motion You can also check the 'actual' maths on the BOSTES answer page, here

[jakesilove]

Hey there, could someone help me with the calculations involved in each of these questions? Both from the 2014 paper, I feel sorry for Jamon and Jake now!

As for your second question, also kinda fucked. We need to find the frequency of the first emitted electron, accounting for the 4.1V. We do this as follows







This get's us the frequency at zero volts! So, we plug that in as our x-intercept, and draw a line with the same gradient (always going to be h) from there. From there, you can go on to estimate etc. to get about 12.8*10^14 Hz

[bethjomay]

As for your second question, also kinda fucked. We need to find the frequency of the first emitted electron, accounting for the 4.1V. We do this as follows







This get's us the frequency at zero volts! So, we plug that in as our x-intercept, and draw a line with the same gradient (always going to be h) from there. From there, you can go on to estimate etc. to get about 12.8*10^14 Hz

I'm sorry, I'm not really sure where your first calculation came from?

[jakesilove]

I'm sorry, I'm not really sure where your first calculation came from?

Fair enough, I was totally unclear aha, too much trauma involved in this question. The graph is in eV (electron volts). So, I had to convert from volts (given. 4.1V) into electron volts (so you just multiply by e, the elementary charge on the electron). Make sense?