In a controlled thermonuclear fusion reactor, the fuel is heated to a temperature of about \(10^{8}\ \mathrm{K}\). At this temperature, the fuel is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → a mixture of positive ions and electrons
At about \( 10^{8}\ \mathrm{K} \) the atoms lose their electrons. The hot mixture of ions and electrons is called a plasma.
NCERT (2026-27):
Controlled thermonuclear fusion – “… In controlled fusion reactors, the aim is to generate steady power by heating the nuclear fuel to a temperature in the range of 108 K. At these temperatures, the fuel is a mixture of positive ions and electrons (plasma). …”