Tjis is probably a stupidly simple question but what exactly do the lower case and upper case phi (the circle with a line through it) stand for, and what is the difference between them? Thanks
Tjis is probably a stupidly simple question but what exactly do the lower case and upper case phi (the circle with a line through it) stand for, and what is the difference between them? Thanks
Going by the CGP book:
Lower case is magnetic flux (i.e. BA) Upper case is magnetic flux linkage (i.e. BAN) and isn't on the syallbus AFAIK - we're supposed to just write Nϕ when we mean magnetic flux linkage.
Wikipedia disagrees, but I don't think it's all that important anyway. Just remember:
Look at the first page. Invigilators were told to announce to everyone to cross out Question 15 and to not attempt answering it.
Also: on the formula sheet, is it just me that the formula for electric potential is confusing? It has too many 'r's from what I'm seeing. Shouldn't the part before Q/r just be a constant, and so it shouldn't include the r!?
It was taken out of the paper since, as you've noticed, the formula for electric potential (which was needed for the question) was wrong on the formula sheet. Of course, it's such a straightforward question, but they had to remove it given the error on the formula sheet.
It was taken out of the paper since, as you've noticed, the formula for electric potential (which was needed for the question) was wrong on the formula sheet. Of course, it's such a straightforward question, but they had to remove it given the error on the formula sheet.
But the same error is present in the 2010 formula booklet, and there was no erratum report for that.
But the same error is present in the 2010 formula booklet, and there was no erratum report for that.
You seem to be right! However, just going through the paper now, there were no questions that required the use of the electric potential formula, hence (I believe) no erratum report was needed.
How do you do this An electron moves due North in a horizontal plane with uniform speed. It enters a uniform magnetic field directed due South in the same plane. Which one of the following statements concerning the motion of the electron in the magnetic field is correct?
A It continues to move North with its original speed.
B It slows down to zero speed and then accelerates due South.
How do you do this An electron moves due North in a horizontal plane with uniform speed. It enters a uniform magnetic field directed due South in the same plane. Which one of the following statements concerning the motion of the electron in the magnetic field is correct?
A It continues to move North with its original speed.
B It slows down to zero speed and then accelerates due South.
C It is accelerated due West.
D It is accelerated due North.
Thanks
I'm guessing it's A because the current and field aren't perpendicular to each other.
Lower case is magnetic flux (i.e. BA) Upper case is magnetic flux linkage (i.e. BAN) and isn't on the syallbus AFAIK - we're supposed to just write Nϕ when we mean magnetic flux linkage.
Wikipedia disagrees, but I don't think it's all that important anyway. Just remember:
ϕ = magnetic flux Nϕ = magnetic flux linkage
and all is well
Oooohhh riiight.. I did get a tad confused by looking on wikipedia Thank you!!
How do you do this An electron and a proton are 1.0 × 10^-10 m apart. In the absence of any other charges, what is the electric potential energy of the electron? A +2.3 × 10^–18J B –2.3 × 10^–18J C +2.3 × 10^–8J D –2.3 × 10^–8J
How do you do this An electron and a proton are 1.0 × 10^-10 m apart. In the absence of any other charges, what is the electric potential energy of the electron? A +2.3 × 10^–18J B –2.3 × 10^–18J C +2.3 × 10^–8J D –2.3 × 10^–8J
A wave of frequency 5 Hz travels at 8 km s–1 through a medium. What is the phase difference, in radians, between two points 2 km apart? help on this Q a) 0 b) pi/2 c) pi d)3pi/2
How do you do this An electron and a proton are 1.0 × 10^-10 m apart. In the absence of any other charges, what is the electric potential energy of the electron? A +2.3 × 10^–18J B –2.3 × 10^–18J C +2.3 × 10^–8J D –2.3 × 10^–8J
The answer is indeed B but your working is a bit confusing - V is electric potential, not energy.
From the formula book:
W=QV
...where W is work required (aka electric potential energy), Q is charge of the electron (as the charge of the proton is part of the field - part of the electric potential!) and V is electric potential.
Combine this with V=4πϵ01rQ
to get
Energy=4πϵ01rQproton×Qelectron
The answer is −2.3×10−18.
EDIT: Note that it's negative force. This is consistent - attractive forces are always negative.
The answer is indeed B but your working is a bit confusing - V is electric potential, not energy.
From the formula book:
W=QV
...where W is work required (aka electric potential energy), Q is charge of the electron (as the charge of the proton is part of the field - part of the electric potential!) and V is electric potential.
Combine this with V=4πϵ01rQ
to get
Energy=4πϵ01rQproton×Qelectron
The answer is −2.3×10−18.
EDIT: Note that it's negative force. This is consistent - attractive forces are always negative.