Answer:
B. QC > 0; QH < 0
Explanation:
Given that there are two reservoir of energy.
Sign convention for heat and work :
1.If the heat is adding to the system then it is taken as positive and if heat is going out from the system then it is taken as negative.
2. If the work is done on the system then it is taken as negative and if the work is done by the system then it is taken as positive.
From hot reservoir heat is going out that is why it is taken as negative

From cold reservoir heat is coming inside the reservoir that is why it is taken as positive

That is why the answer will be
,
Answer:drift velocity is 1.7*10^-4m/s and number of charge is 2.7*10^-24
Explanation:
Answer:
19.01 N
Explanation:
F = Force being applied to the crate = 45 N
= Angle at which the force is being applied = 
Horizontal component of force is given by

The horizontal component of the force acting on the crate is 19.01 N.
Answer:
potential energy
Explanation:
this is because potential energy= mgh
so when m= 2m
p.e. = 2 times the previous value
Therefore , When mass is doubled , Potential energy gets doubled. When mass is halved , Potential energy decreases by half.