Answer: Why does the cord of an electric heater not glow while the heating element does? The heating element of the heater is made up of alloy which has very high resistance so when current flows through the heating element, it becomes too hot and glows red. But the resistance of cord which is usually of copper or aluminum is very low so it does not glow.
Explanation:
Answer:
Option (B) is correct.
Explanation:
Given that the molecules of hydrogen gas (
) react with molecules of oxygen gas (
) in a sealed reaction chamber to produce water (
).
The governing equation for the reaction is

From the given, the only fact that can be observed that 2 moles of
and 1 mole of
reacts to produce 2 moles of
.
As the mass of 1 mole of
grams ... (i)
The mass of 1 mole of
grams ...(ii)
The mass of 1 mole of
grams (iii)
Now, the mass of the reactant = Mass of 2 moles of
+ mass 1 mole of 
[ using equations (i) and (ii)]
grams.
Mass of the product = Mass of 2 moles of 
[ using equations (iii)]
=36 grams
As the mass of reactants = mass of the product.
So, mass is conserved.
Hence, option (B) is correct.
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Nuclear fusion reactions convert protons into helium; thus, becoming the source of all energy radiated by the sun.
Answer: Option D
<u>Explanation:</u>
Nuclear fusion reaction is one among the two nuclear reactions in which the atoms nucleus interact with each other to produce the products. In nuclear fusion, two smaller atoms react together to form a new atom with bigger size.
So large amount of energy is required to start the nuclear fusion reaction. The fusion reactions mostly occurs in stars. The illumination in Stars even the Sun is due to nuclear fusion reaction occurring with the atoms present in them.
Mostly the energy radiated by Sun is due to the protons-protons chain reaction. In this chain reaction, the protons get converted into helium due to nuclear fusion reaction, thus becoming the source of all energy radiated by the Sun.