AQA Physics PHYA4 - 20th June 2016 [Exam Discussion Thread]

I used the equation too. Do you remember what you got for your capacitance?

Wasn't it V = -mv/N?

Here are my answers to Written, the question parts might not be correct.

Written answers
1ai) 8.26 (will be a range)
ii) 2.6x10^-4

bi)28
ii)5.9x10^4
iii) bottom box ticked

2ai) Derivation
ii) 6.06x10^6 (3SF only)

b) Downward Curve staring at 9.81
Minimum at zero at a point slightly offset from halfway closer to Venus
Rises up to 8.87

3a) V=mv/N

b) Derivation

ci) 1.15x10^-19 kgms-1 OR Ns

cii) Anti electron neutrino released also so Beta minus particles have range of Kinetic Energies upon release.

4a) Small amplitude oscillation as only valid for small angular amplitudes.

b) -Set up light string with Bob on the end,
attach top of string to clamp stand boss.
-Measure length from top to centre of Bob.-Release the Bob so it oscillates with small amplitude.
-Use stop clock to measure time taken for 20 oscillations.
-Divide this by 20 for mean T
-Plot T^2 against L
-Calc Gradient
g=(4pi^2)/gradient
-Repeat procedure

c) -Student value 4x true value
-Time period half so all values for T^2 will be 1/4 the true
-Gradient is 4x lower
-State equation or show that g is inversely proportional to gradient.

5a) Lenz's Law: Direction of induced EMF/current is always in a direction that opposes the change that caused it.
Faraday's Law: Induced EMF is proportional to rate of change of flux linkage.

b) -Change in flux linkage when current flows.
-EMF induced in wheel (or whatever it was called)
-Current induced in the wheel as good conductor.
-Current carrying conductor (wheel) opposes the field due to coil, therefore there is a force against the direction of motion.

c) Wheel not in contact with electromagnet so no wear, but in brake pads there is wear due to friction.

More energy used or less effective or heating.

I think both answers for increased power drain and electrical failure will be valid. Although my view is that it would be unreasonable to use a powered braking system, because if you park your car on a hill your battery will eventually go flat and then your car will have f***Ed off down the hill by the time you come back with your shopping.

Wasn't it V = -mv/N?

That's what I got (rounded of course).

And it would be in farads, not coulombs

what did people say for the effect when that guy recorded only half of T? was it (1/4)g?

What was the unit - I worked it out to be C^2 kg^(-2)?

No because they're in opposite direction. So NV - mv = 0

Nope. Because V is a magnitude.

Wasn't it V = -mv/N?

Was it A ?

did people get the resuklt for g would be 4x larger not less

did people get the resuklt for g would be 4x larger not less

Wasn't it V = -mv/N?

That's what I got (rounded of course).

And it would be in farads, not coulombs

Okay assuming I'd completed the question thinking N was that of the original, would I only lose marks on the 4-marker proof question or any of the ones following? Do you guys remember what the follow-up ones were?

i got 8microfards but i have feeling i might be out of range