The efficiency of a heat engine is given by the expression 
The efficiency of a heat engine is the ratio of the work done by the engine to the heat given as the input to the engine.
The heat engine absorbs Q h from the hot reservoir , performs a work <em>W</em> on the absorbed heat and rejects Qc to the cold reservoir.
Therefore, the work done is given by,
Thus the efficiency is given by,
A. The Sun is the only star in the Solar System. This is the only star we know of.
I hope this helps!!
The spheres in the experiment could not be of equal size.
<u>Explanation:</u>
This is the concept of Electrostatics. The two metal spheres are placed on portable insulated stand so initially both have charge, q = 0. We thought to create equal and opposite charges on both the metal spheres without touching the charged glass rod to these spheres. First of all let us hold the rod at a distance R from any of the insulated sphere, making it closer to the spheres the phenomenon of induction arises. Finally the sphere near the rod will have induced opposite charges and the other sphere which is away from rod will get induced same charge of the rod. And in this process we will get opposite and equal charges in the spheres without touching them. No, it is not necessary to be the spheres of equal size.
3. All are hydrocarbons and all are in the eth- group i.e. all have two carbon atoms. Ethane is an alkane, ethene is an alkene and ethyne is an alkyne.
4. No C=C double bonds, only single C-C bonds. Saturated with hydrogen atoms (as many C-H bonds as possible).
5. As branching increases, boiling points decrease. (Molecules exert intermolecular forces of attraction between each other and these are stronger when they are closer together. Branching makes it harder for the hydrocarbon molecules to pack closely together therefore these forces are weaker and it takes lesser energy to break them.)
