Need help with A2 physics unit 4 multiple choice exam paper questions

Bump, I would be very grateful if someone could help me out ASAP if they could, ask the exam is tommorrow, thanks.

Not sure if this is in the right section of the forum, but not sure how to move threads?

For the first one, the circumference of the earth is 1.5 x10^8 x 1000 x 2pi, and the time the earth takes to travel this distance is 365 x 24 x 60 x60. Then we're just using V = s/t to find the speed.
The second one, in order to induce an EMF in the secondary coil, there must be a change in the magnetic flux of the primary coil. The magnitude of this induced EMF is equal to the rate of this change, so when the switch is turned off suddenly the change is more rapid than when the current is building up initially, meaning the magnitude of the induced EMF is greater.
The last question, they're essentially asking you how kobg it takes for the voltage of the capacitor to drop to 90% of its original value. They tell you the initial current and voltage, so you can find the resistance and therefore
T = RCln0.9
Posted from TSR Mobile

Hi, many thanks for explaining that, but I just have a few questions on your explanations for them.


24) (the second one) - but surely if the emf induced is maxed at this value, then induced current will be at its smallest value (from P = IV)?

14) also would you be able to explain this one, it's on the third page with 16) (I think you missed this one out)

Thanks