Why does a needle have a sharp point ?

Why does a knife have a sharp edge and a needle has a sharp tip ?

Why does trachea have 'C' shaped rings of cartilage?

Why does human being have an important place in the environment?

Why does an individual have only two alleles even if a character shows multiple allelism?

What does a polynucleotide have at 3'end.

Why do the veins have valves?

Give scientific reasons. Why does a thick wire have low resistance?

Take the inside tray of a used up match box and place a small magnetic needle inside the tray . Now take a long connecting wire and wind it around the tray . Complete the electric circuit ny connecting in it , this wire , electric cell , plug key and a bulb as shown in the below figure .: Mark the position of the magnetic needle . take a bar magnet near to the magnetic needle . keep looking at the needle and close the plug key . the bulb will light up , and you will realize that the current has started flowing . does the magnetic needle change its position ? :

Why does the wave theory of light fail to explain the photoelectric effect.

Answer the following : Why does car uses a battery instead of a cell ?