Summer 2003 17 i forgot the method, b'because i had done this long back,
Summer 200721 is B because light rays bend(refract) when they move from 1 median to another,
As water is denser than air so the rays refract away from the normal ray.
30 is also B, as potentiometer requires 3 ways input so we eliminates A and D. About C its not correct as the current will flow through the wire because it has less resistant, and current always flow through the easiest path(less resistant) so B is correct.
Winter 2007 21 is B. It is because as B line is passing through center, if you cut the half of the above and fill it it the gap which the between of 2 trough, you will get the normal water line ( Sorry, i don't know how to explain, but this is my own theory and is Common sense
)
Summer 200529 is D because as the voltmeter is always connected in parallel to the object whose voltage is to be measured.
32 is B. Its due to Variable resistor doesn't work in parallel.
Winter 200531 is A,
Current always flows through the easiest way, way which is of less resistance. So when S is closed, the current pass through the S part instead through resistor, so the brightness increases.
