Answer:
B. 6 cm
Explanation:
First, we calculate the spring constant of a single spring:

where,
k = spring constant of single spring = ?
F = Force Applied = 10 N
Δx = extension = 4 cm = 0.04 m
Therefore,

Now, the equivalent resistance of two springs connected in parallel, as shown in the diagram, will be:

For a load of 30 N, applying Hooke's Law:

Hence, the correct option is:
<u>B. 6 cm</u>
We shall consider two properties:
1. Temperature difference
2. Thermal conductivity of the material
Use a cylindrical rod of a given material (say steel) which is insulated around its circumference.
One end of the rod is dipped in a large reservoir of water at 100 deg.C and the other end is dipped in water (with known volume) at 40 deg. C. The cold water if stored in a cylinder which is insulated on all sides. A thermometer reads the temperature of the cold water as a function of time.
This experiment will show that
(a) heat flows from a region of high temperature to a region of lower temperature.
(b) The thermal energy of a body increases when heat is added to it, and its temperature will rise.
(c) The thermal conductivity of water determines how quickly its temperature will rise. If mercury replaces water in the cold cylinder, its temperature will rise at a different rate because its thermal conductivity is different.
Answer : (B) Prominence
Explanation :
A large, glittering and gaseous characteristic which is extending outward from the surface of the sun is called <em>Prominence</em>.
<em>Photosphere</em> is one of the layer of sun where the prominence are anchored and then they move into the corona of the sun.
<em>Corona</em> is a region in the surface of the sun which is the constituent of hot ionized gases (plasma).
The prominence consists of colder plasma and this prominence plasma is much more shining and denser as compared to coronal plasma.
Hence, the correct option is (B) Prominence.
The heat is transferred to one material to another, however insulators minimize that transfer, keeping it in the area, warming it.