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

Reply 1180

chem@uni

9

what is definition for 1 parsec?

Reply 1181

kate8

2

Original post by chem@uni

what is question?

If capacitors of different capacitance were in parallel would they still discharge at the same rate. Or because the current through them is different the one with the greater capacitance discharges faster?

Reply 1182

jcwh97

2

Original post by buxtonarmy

Thanks bro so how would I do 4bi on this paper? It's similar and I still struggle

http://www.ocr.org.uk/Images/65365-question-paper-unit-g485-fields-particles-and-frontiers-of-physics.pdf

0.15 x speed of light

Use the change in wavelength formula

Reply 1183

kate8

2

Original post by chem@uni

what is definition for 1 parsec?

distance that gives a parallax angle of 1arcsecons

Reply 1184

jcwh97

2

Original post by chem@uni

what is definition for 1 parsec?

The distance from the baseline of 1AU that subtends an angle of 1 arc second.

Reply 1185

Chung224

13

Original post by kate8

If capacitors of different capacitance were in parallel would they still discharge at the same rate. Or because the current through them is different the one with the greater capacitance discharges faster?

Where RxC the resistance will decrease if put in parallel.... hence the time constant increases this means that the rate of change of V,Q or I must decrease as a larger time to fall to 1/e of its initial value hence the initial rate of discharge will decrease

Oops sorry thought you said resistance, capacitors work the same way, if put in parallel, total capacitance increases to larger time constant same explanation

(edited 8 years ago)

Reply 1186

jcwh97

2

Original post by jamesbird18

Can somebody please help me? If we get a question that involves,say a proton moving from left to right would you say the current is moving left to right or not? Could alter any answer using FLHR thats all

The current flows in the same direction as the protons and opposite to electrons.

Reply 1187

ForgottenApple

14

Original post by Chung224

Where RxC the resistance will decrease if put in parallel.... hence the time constant increases this means that the rate of change of V,Q or I must decrease as a larger time to fall to 1/e of its initial value hence the initial rate of discharge will decrease

that makes no sense to me

Reply 1188

Chung224

13

Original post by ForgottenApple

that makes no sense to me

Which part bro? :smile:

Reply 1189

chem@uni

9

Can someone explain how I got from
s-1 Hubbles constant to
kms-1 Mpc-1

Reply 1190

fnatic NateDestiel

18

Original post by chem@uni

what is definition for 1 parsec?

The distance that gives a stellar parallax 1 second of arc.

Reply 1191

nothepreacher

18

Original post by ETRC

-intensifier absorbs x-rays by photographic film
-scintillator is used as an intensifier
-scintillator converts x-ray photon into many photons of visible light
-photons of visible light releases electrons so a lower exposure time to x-rays is needed
-gives a sharper images

Hey do you know which has greater energy - a pair production x ray or a compton effect x ray?

Reply 1192

Smug Life

12

Original post by chem@uni

Can someone explain how I got from
s-1 Hubbles constant to
kms-1 Mpc-1

Still on 2010?

Reply 1193

randlemcmurphy

11

Original post by Chung224

Where RxC the resistance will decrease if put in parallel.... hence the time constant increases this means that the rate of change of V,Q or I must decrease as a larger time to fall to 1/e of its initial value hence the initial rate of discharge will decrease

Oops sorry thought you said resistance, capacitors work the same way, if put in parallel, total capacitance increases to larger time constant same explanation

If the resistance decreases shouldn't the time constant...?

Reply 1194

JayGreen

1

Original post by nothepreacher

Hey do you know which has greater energy - a pair production x ray or a compton effect x ray?

pair production x-ray has the highest frequency, E= hf so id say the pair production x-ray

Reply 1195

chem@uni

9

Original post by Smug Life

Still on 2010?

What do you mean?

Reply 1196

actanide

2

Original post by randlemcmurphy

If the resistance decreases shouldn't the time constant...?

yeah thats what i was thinking: t is proportional to C and R so if C decreases so much t

Reply 1197

stargazer678

could someone show me what a good drawing is for the definition of a parsec? (has the sun, earth, star, AU in!)

Reply 1198

ETRC

17

Original post by nothepreacher

Hey do you know which has greater energy - a pair production x ray or a compton effect x ray?

pair production is highest- they involve high energy x-rays being released

then its compton

photoelectrons from photoelectric have least energy

my brain hurts now from revising for 7 hours with a 30min break -.-