When a sound source approaches you, how does the pitch change?

The pitch increases

Explanation:

This effect is called Doppler effect. Doppler effect occurs when the source of a wave (such as a sound wave) moves relative to a stationary observer. In particular, two situations can occur:

- When the sound source moves towards the observer, there is a decrease in the apparent wavelength as seen from the observer; since frequency is inversely proportional to wavelength, the observer hears a sound with apparent higher frequency, which corresponds to a higher-pitch sound.

- When the sound source moves away from the observer, there is an increase in the apparent wavelength as seen from the observer; since frequency is inversely proportional to wavelength, the observer hears a sound with apparent lower frequency, which corresponds to a lower-pitch sound.

In this case, the sound source is approaching you: so we are in the 1st situation, therefore the pitch of the sound increases.

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .