Question

A device that converts energy of combustion of fuels like hydrogen and methane, directly into electrical energy is known as
A.Dynamo
B.$Ni - Cd$ cell
C.Fuel cell
D.Electromagnetic cell

Answer 1

Hint:
The combustion of fuels like hydrogen and methane can release large amounts of heat. This heat can be used to power various energy dependent processes. The electrodes are usually gases that are stored in tanks.

Complete answer:
Fuel cells are like batteries. They use gases like hydrogen, oxygen, methane and others. These gases undergo combustion and the heat produced from this combustion is converted into electricity. These cells do not require recharging and can produce electricity until there is fuel.
The most common fuels used are Hydrogen stored at the anode and the oxygen gas at the cathode.
The reactions that take place at the cathode and anode are:
Cathode: ${O_2} + 4{H^ + } + 4{e^ - } \to 2{H_2}O$
Anode: $2{H_2} \to 4{H^ + } + 4{e^ - }$
Therefore, joining both the reactions, we can get the net reaction that is taking place in the fuel cell that is,
${O_2} + 2{H_2} \to 2{H_2}O$
The above reactions show that this cell takes electrons from the cathode that is, hydrogen and passes it on to the oxygen. Therefore, water vapour is produced at the cathode. The heat produced from the reactions can be converted into electric energy.
Fuel cells are highly efficient and can conserve up to $74\% $ of the energy that is created. It has a prominent role in space travel as the fuel is generally easy to access and it also has the added benefit of being more efficient that other cells. It belongs to the group of cells known as secondary cells.
dynamo is used to create direct current. It is a generator.
Nickel Cadmium cell is a cell that can be recharged again. It is made of nickel and cadmium electrodes. It is used in flash photography and flashlights.
Electromagnetic cells are an odd option since it does not exist. There is no such thing as electromagnetic cells.
Therefore the answer to the question will be option C that is, fuel cells.

Note: Hydrogen gas is present in cathode. The anode is oxygen. The electrodes are separated by a center container that is filled with an electrolyte that is, $KOH$ .
-Electrons are removed from hydrogen gas.
-This cell is highly efficient.