Help with this question please I'm at a crossroads. (1 Viewer)

[BoardofBoards1]

Ffs so now what do we put if this comes up
How do we know if its testing syllabus knowledge or an oos trick question? I HATE THIS OVERSIMPLIFIED SYLLABUS
I will censor explanation so yall read at your own risk

Yes I completely agree, I've had similar frustrations with a particular eddy currents question I believe was 2005 hsc Q9. Honestly we just have to follow the HSC dotpoints and assumptions as if we're their lapdogs so, I can only recommend that everyone should familiarise themselves with the tricks and idiosyncracies of the HSC syllabus.

 

[C2H6O]

Yes I completely agree, I've had similar frustrations with a particular eddy currents question I believe was 2005 hsc Q9. Honestly we just have to follow the HSC dotpoints and assumptions as if we're their lapdogs so, I can only recommend that everyone should familiarise themselves with the tricks and idiosyncracies of the HSC syllabus.

I am about to go full coolcat monologue mode rn

 

[C2H6O]

Yes thank you, I appreciate all the replies I recieved, however, the problem I still have is that the general statement "the secondary voltage is the first derivative of the primary voltage" I feel is kind of unheard of.

just to make sure you understand the reasoning for the expected answer B,
voltage is directly proportional to current (V=IR applies here within the syllabus)
current is directly proportional to magnetic field (B=μNI/L)
magnetic field is directly proportional to flux (Φ=BA)
emf is proportional to the derivative of flux over time (ε=-N Δφ/Δt, Δ is the same as saying d)
emf is equivalent to voltage

therefore secondary voltage is proportional to the derivative of primary voltage

 

[BoardofBoards1]

just to make sure you understand the reasoning for the expected answer B,
voltage is directly proportional to current (V=IR applies here within the syllabus)
current is directly proportional to magnetic field (B=μNI/L)
magnetic field is directly proportional to flux (Φ=BA)
emf is proportional to the derivative of flux over time (ε=-N Δφ/Δt, Δ is the same as saying d)
emf is equivalent to voltage

therefore secondary voltage is proportional to the derivative of primary voltage

Yes I got it now, thanks for your time man, but just a tiny quick note, V=IR cannot be used for regular or in almost all cases of inductive circuits, as Ohm's law only applies to simple resistor circuits, hence that's why faraday's law exists, which may also be a common misconception.

A simple explanation you may come across is "The simple answer is, that a transformer doesn't obey ohms law because it isn't a resistor". And in most ideal cases, the resistance of transformers is irrelevant in yielding significant values.

 

[C2H6O]

just a tiny quick note, V=IR cannot be used for regular or in almost all cases of inductive circuits, as Ohm's law only applies to simple resistor circuits, hence that's why faraday's law exists, which may also be a common misconception.

yes this is even an AC circuit which would have sht like impedance and self inductance, but im assuming for hsc this is where they want our train of thought to be. regardless the purpose of me saying v=ir is to illustrate that they're proportional for syllabus purposes even in an AC solenoid

 

[BoardofBoards1]

yes this is even an AC circuit which would have sht like impedance and self inductance, but im assuming for hsc this is where they want our train of thought to be. regardless the purpose of me saying v=ir is to illustrate that they're proportional for syllabus purposes even in an AC solenoid

Oh right I understand my bad, yes that would be a good train of thought.

 

[wizzkids]

This question from CSSA is outside the HSC Physics syllabus.
The correct answer is (A). (the CSSA wouldn't have a clue)
To properly understand it requires a more detailed knowledge of AC circuit theory, (factors like self-inductance as others have said).
The difficulty is the inputs and outputs of the transformer have been expressed as voltages, and in inductors, the current and the applied voltage are out-of-phase. The input current I lags behind the emf V by 90 degrees, and it is the current that determines the magnitude of the magnetic flux.
Anyway, with that help, here is the answer:
For a transformer, the phase relationship between the primary voltage and the secondary voltage is either 0 degrees (in phase) or 180 degrees (out of phase) depending on whether the primary winding and the secondary winding are in the same direction or opposite direction relative to the changing magnetic flux. The amplitude of the secondary voltage depends on the turns ratio of 0.25