dnaamani
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For the graph question in the markscheme it says Io must be 2mA and the time must be 0.02 - 0.06 s
But i didnt understand why

And the answer for the multiple choice is (A) but please explain
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dnaamani
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The answer is B but I didn't understand it
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Elaria
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For question 15:
to find Io --> I=V/R
V=10 V and R=5000 ohms
10/5000= 2x10^-3 A which is the same as 2mA

I am not sure of q2
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Elaria
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As for question 6 :
---when the switch is closed the current flows through the coil
---the current in the coil generates a magnetic field
---when the switch is opened current drops
---so there is a rate of change in the magnetic flux in the coil Y which will link to coil X so an emf will be induced
--- induced emf= -d(flux linkage)/d(time)
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Eimmanuel
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(Original post by dnaamani)
But i didn't understand why

And the answer for the multiple choice is (A) but please explain
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The blue dots in the diagram indicate the direction of the magnetic field which is out of the plane - towards you.
Using Fleming Left Hand Rule, the magnetic force is deduced to be in the direction as shown by the black arrows.
The magnetic force would "shrink" the loop which explains why the answer is (A).
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dnaamani
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June 2014 (R) q 7

A capacitor of capacitance C has a potential difference V across it. The energy stored on the capacitor is Z joules. A second capacitor of capacitance C/2 has a potential difference 2V across it.
The energy stored on the second capacitor is :

The answer is " 2Z " but i couldn't figure out why
help please
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Elaria
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(Original post by dnaamani)
June 2014 (R) q 7

A capacitor of capacitance C has a potential difference V across it. The energy stored on the capacitor is Z joules. A second capacitor of capacitance C/2 has a potential difference 2V across it.
The energy stored on the second capacitor is :

The answer is " 2Z " but i couldn't figure out why
help please
The energy stored in the first capacitor--> Z=1/2CV2
The energy stored in the second capacitor--> Z'=1/2xC/2x(2V)2
= 1/2 x 1/2 x 4 x CV2
= CV2
Therefore Z' = 2Z

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dnaamani
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A car is repeatedly driven over a bridge at gradually increasing speeds. Above a certain speed the car loses contact with the road at X.
State why this happens.

The mark scheme says:
An answer that either states implicitly or implies that
'The required centripetal force > mg and so cannot be provided'.

but i didn't really understand what they meant
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dnaamani
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What is the acceleration of a proton in an electric field of strength 4.0 x 10^4 Vm^-1?
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Elaria
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(Original post by dnaamani)
What is the acceleration of a proton in an electric field of strength 4.0 x 10^4 Vm^-1?
use F=EQ to find F then substitute your value in a=F/m , where m is the mass of the proton.
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Elaria
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(Original post by dnaamani)
A car is repeatedly driven over a bridge at gradually increasing speeds. Above a certain speed the car loses contact with the road at X.
State why this happens.

The mark scheme says:
An answer that either states implicitly or implies that
'The required centripetal force > mg and so cannot be provided'.

but i didn't really understand what they meant
When the car loses contact with the road, the only force acting on the car is its weight. So in order for the car to keep contact with the road is for the centripetal force to be greater than the weight which is not possible.

Spoiler:
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I'll be sitting for the exam on the 9th wish me good luck *Nervous*
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