PHYA4 Troubles.
hey, just 2 quick questions i'm really stuck on from June 2010 PHYA4 paper. Maybe 3.
http://filestore.aqa.org.uk/subjects/AQA-PHYA4-2-W-QP-JUN10.PDF
Firstly, question 2ai... figure 1 shows a circuit with a negatively charged sphere... the sphere moves to the top of the plate, suggesting that the top plate is positively charged... so could the electric field flow from bottom to top? (charge flows from negative to positive?) The answer says that electric field is directed from top to bottom.
Secondly, question 4a shows an electron travelling in circular motion, along a horizontal plane, and asks which direction the magnetic field acts.
I know it must be either upwards through the plane or downwards through the plane, but i'm not sure which or why.
finally, the very last question on the paper, asks why the induced EMF in a coil is greatest when the flux linkage is zero... and i don't know why?
the mark scheme says that as the coil is parallel to 'B', the rate of change of flux linkage is the greatest, but surely the opposite is true? isn't the rate of change of flux linkage greatest when the coil is perpendicular to B, as more electric field lines can pass through the coil?
Any help would be massively appreciated. again.
http://filestore.aqa.org.uk/subjects/AQA-PHYA4-2-W-QP-JUN10.PDF
Firstly, question 2ai... figure 1 shows a circuit with a negatively charged sphere... the sphere moves to the top of the plate, suggesting that the top plate is positively charged... so could the electric field flow from bottom to top? (charge flows from negative to positive?) The answer says that electric field is directed from top to bottom.
Secondly, question 4a shows an electron travelling in circular motion, along a horizontal plane, and asks which direction the magnetic field acts.
I know it must be either upwards through the plane or downwards through the plane, but i'm not sure which or why.
finally, the very last question on the paper, asks why the induced EMF in a coil is greatest when the flux linkage is zero... and i don't know why?
the mark scheme says that as the coil is parallel to 'B', the rate of change of flux linkage is the greatest, but surely the opposite is true? isn't the rate of change of flux linkage greatest when the coil is perpendicular to B, as more electric field lines can pass through the coil?
Any help would be massively appreciated. again.
Original post by physicso
hey, just 2 quick questions i'm really stuck on from June 2010 PHYA4 paper. Maybe 3.
http://filestore.aqa.org.uk/subjects/AQA-PHYA4-2-W-QP-JUN10.PDF
Firstly, question 2ai... figure 1 shows a circuit with a negatively charged sphere... the sphere moves to the top of the plate, suggesting that the top plate is positively charged... so could the electric field flow from bottom to top? (charge flows from negative to positive?) The answer says that electric field is directed from top to bottom.
Secondly, question 4a shows an electron travelling in circular motion, along a horizontal plane, and asks which direction the magnetic field acts.
I know it must be either upwards through the plane or downwards through the plane, but i'm not sure which or why.
finally, the very last question on the paper, asks why the induced EMF in a coil is greatest when the flux linkage is zero... and i don't know why?
the mark scheme says that as the coil is parallel to 'B', the rate of change of flux linkage is the greatest, but surely the opposite is true? isn't the rate of change of flux linkage greatest when the coil is perpendicular to B, as more electric field lines can pass through the coil?
Any help would be massively appreciated. again.
http://filestore.aqa.org.uk/subjects/AQA-PHYA4-2-W-QP-JUN10.PDF
Firstly, question 2ai... figure 1 shows a circuit with a negatively charged sphere... the sphere moves to the top of the plate, suggesting that the top plate is positively charged... so could the electric field flow from bottom to top? (charge flows from negative to positive?) The answer says that electric field is directed from top to bottom.
Secondly, question 4a shows an electron travelling in circular motion, along a horizontal plane, and asks which direction the magnetic field acts.
I know it must be either upwards through the plane or downwards through the plane, but i'm not sure which or why.
finally, the very last question on the paper, asks why the induced EMF in a coil is greatest when the flux linkage is zero... and i don't know why?
the mark scheme says that as the coil is parallel to 'B', the rate of change of flux linkage is the greatest, but surely the opposite is true? isn't the rate of change of flux linkage greatest when the coil is perpendicular to B, as more electric field lines can pass through the coil?
Any help would be massively appreciated. again.
last one first -
is a top down view of the coil - the sections cutting the flux would be projecting down into the page from each visible end. when the angle of the top of the coil to the B field is 90 degrees those sections are moving parallel to the flux and not cutting it.
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