help in physics

[mushairif]

i need help in a physics october november 2005 paper 1 past paper
Question 15 says that :
A knife is being sharpened on a rotating sharpening-stone. A spark flies off and lands on the
operator’s hand. The spark is a very hot, very small piece of metal. The operator feels nothing.
What does this show about the piece of metal?
A It has a high thermal capacity.
B It has a low thermal capacity.
C It is a good conductor of heat.
D It is a poor conductor of heat.

I dont know why the answer in the marking shceme is B

 

[Zohaib Sherazi]

C and D can clearly not be the answers as a metal is a conductor anyways, and the situation already mentions that the metal is hot. The subject of the question is why didn't the hand feel it. So the concept of the metal being a conductor or non conductor is irrelevant. So, we eliminate C and D. Secondly, if something has a high thermal capacity then it can transfer heat to a large extent. But in the case of having a low thermal capacity it cannot. The effect is very localized and the hand doesn't feel it.

Consider pouring a drop of hot tea on your hand and a cup of hot tea on your hand. Obviously the whole cup of hot tea does more damage due to its large thermal capacity.

 

[mushairif]

thanks for your help

 

[shoaib672002]

Igniting the oldest post in the IGCSE forum!!!