Physics - Electricity, Waves and Weight

anpanman SG

1. Firstly

In the circuit shown, the P.D between X and Y is 15 V. What is the current flowing through the 1 ohm resistor?

I know this is an easy question but still I am confused of some parts. Since P.D across parallel circuit is the same, so is the P.D across each brance 7.5 V? or is it 15 V still? Hmm, I got the answer as 5.0 A but my working seems wrong.

I simply used 15 V/3 (first branch) = 5A. however, I strongly think that P.D should be 7.5 V. Or maybe I'm wrong, but please tell me why.

2.Gravitational field strength

A will affect mass of an object

B will affect weight of an object

I wrote B but my ans scheme is A. Is there some mistake?

3.The frequency of a sound wave is affected by

(i) Wind speed

(ii) Medium of travel

(iii) frequency of vibration of source

Choose any of the above, you may choose more than 1.

Answer is only (iii). Can someone care to explain?

Thank you very very very very very much!

eagle SG

still 15 V

It's about potential difference across 2 points. And for parallel circuits, they are the same.

2.Gravitational field strength

A will affect mass of an object

B will affect weight of an object

I wrote B but my ans scheme is A. Is there some mistake?

Answer is definitely B

3.The frequency of a sound wave is affected by

(i) Wind speed

(ii) Medium of travel

(iii) frequency of vibration of source

Choose any of the above, you may choose more than 1.

Answer is only (iii). Can someone care to explain?

(i) wind speed doesn't affect frequency, only wavelength

(ii) same as above

Because frequency is how many times in one second. It depends on the source. No matter how much the "resistance", the number of "beats" coming per second still remains... can't change...

The same for light waves.