# OCR Physics A G485 - Frontiers of Physics - 18th June 2015Watch

3 years ago
#1061
(Original post by rw99)
on the june 2011 paper Q5a how are you supposed to work out the force is downwards? Obviously you use the left hand rule but i can't find where in the question it gives you the information you need. You're given the direction of the current but it just says the magnetic field is perpendicular to it, it doesn't give you its direction. I guessed and went with upwards but it's downwards. Any ideas?
yes they do, they give you the circuit, so you can find out the conventional current, and they give you the field direction, all you gotta do is stick your fingers the right way up
0
3 years ago
#1062
(Original post by rw99)
on the june 2011 paper Q5a how are you supposed to work out the force is downwards? Obviously you use the left hand rule but i can't find where in the question it gives you the information you need. You're given the direction of the current but it just says the magnetic field is perpendicular to it, it doesn't give you its direction. I guessed and went with upwards but it's downwards. Any ideas?
It does give you the direction of the magnetic field, take a closer look at the diagram.
0
3 years ago
#1063
(Original post by I Persia I)
Do we need to know that Americium-241 is the source in smoke detectors? O.o
i think so
they sometimes ask you for a common medical tracer like iodine-131
0
3 years ago
#1064
Right the random nature of radioactive decay means you cannot 'predict' when a nucleus will decay or which nucleus will decay. Isn't predict the wrong word, you can still predict but you'll probably predict wrong?
0
3 years ago
#1065
June 11 Q1: why isn't the secondary coil's e.m.f. alternating?
0
3 years ago
#1066
(Original post by randlemcmurphy)
It does give you the direction of the magnetic field, take a closer look at the diagram.
yeh thanks just seen it- i mistook those little arrows to be showing the current direction (which you can work out anyway so i don't know why i didn't think this was strange).

Thanks!
0
3 years ago
#1067
(Original post by rw99)
on the june 2011 paper Q5a how are you supposed to work out the force is downwards? Obviously you use the left hand rule but i can't find where in the question it gives you the information you need. You're given the direction of the current but it just says the magnetic field is perpendicular to it, it doesn't give you its direction. I guessed and went with upwards but it's downwards. Any ideas?
The question tells you the particle is describing circular motion so the force has to be towards the centre. So you have current and force just use your hand to find field direction.
0
3 years ago
#1068
(Original post by Elcor)
June 11 Q1: why isn't the secondary coil's e.m.f. alternating?
It is, why do you think it isn't?
0
3 years ago
#1069
hello guys!!
Can someone give me a good answer of describe ultrasound scanning???
i dont really get the mark scheme one relating it with the book.
Thanks
0
3 years ago
#1070
(Original post by Raizel)
https://86702370e68cc0f4d10e729b4f36...%20A-level.pdf

6bii part 1
can someone explain to me the reason of that method of calculation to achieve the answer.
Power = Intensity x Area

Area = 4 x pi x r^2
Intensity = 1400

Substitute and multiply.
0
3 years ago
#1071
(Original post by dragozox)
hello guys!!
Can someone give me a good answer of describe ultrasound scanning???
i dont really get the mark scheme one relating it with the book.
Thanks
An ultrasound transducer emits pulses of ultrasound into the patient/body.
The pulses of ultrasound are reflected at the boundary of tissue.
The intensity of the reflected signal depends on the acoustic impedance at the boundary.
The delay time of the ultrasound is used to determine the depth of tissue.

That is what I remember from mark schemes. If it asks about B-scans its the same thing other than it involves using different angles and directions.
0
3 years ago
#1072
Does anyone have june 2014 g485 mark scheme?
0
3 years ago
#1073
Hey guys I got 84/100 in Jan 2012 and I want to know what ums that would be if A is 73 and B is 66.
0
3 years ago
#1074
I just don't understand magnetic fields 😢 someone help me, what do we need to know about magnetic fields and what are we expected to apply?

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0
#1075
(Original post by leroythelost)
Hey guys I got 84/100 in Jan 2012 and I want to know what ums that would be if A is 73 and B is 66.
142 ish
0
3 years ago
#1076
(Original post by jcwh97)
An ultrasound transducer emits pulses of ultrasound into the patient/body.
The pulses of ultrasound are reflected at the boundary of tissue.
The intensity of the reflected signal depends on the acoustic impedance at the boundary.
The delay time of the ultrasound is used to determine the depth of tissue.

That is what I remember from mark schemes. If it asks about B-scans its the same thing other than it involves using different angles and directions.
cheers!!!

good luck with tomorrow!!!!
0
3 years ago
#1077
(Original post by BrokenS0ulz)
It is, why do you think it isn't?
Part d.ii, it says the lamp has a p.d. of 11.8V and you later have to calculate the current in the secondary circuit; surely this implies a constant e.m.f.?
0
3 years ago
#1078
(Original post by L'Evil Fish)
142 ish
Still repping the phy crew proud

0
3 years ago
#1079
Hey guys, can someone give me the definition of :

Activity -
Decay constant -
0
3 years ago
#1080
(Original post by DoctorDren)
Does anyone have june 2014 g485 mark scheme?

I dont know if this is allowed but here it is
0
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