A graph of the variation with nucleon number \(A\) of the binding energy per nucleon is shown.
What is the approximate total energy, in MeV, needed to completely separate the nucleons of a \(^{180}_{72}\mathrm{Hf}\) nucleus?
Correct Answer: \( \boxed{\mathrm{C}} \)
The total binding energy of a nucleus is given by
\(\mathrm{binding\ energy}=(\mathrm{binding\ energy\ per\ nucleon})\times A\)
For \(A=180\), the graph gives a binding energy per nucleon of approximately \(8.0\,\mathrm{MeV}\).
Therefore,
\(E_{\mathrm{B}}\approx 8.0\times180\)
\(E_{\mathrm{B}}\approx1440\,\mathrm{MeV}\)
The energy required to completely separate the nucleons is equal to the total binding energy of the nucleus.
Hence, the correct answer is \( \boxed{\mathrm{C}} \).
Which two components of a nuclear power station are primarily responsible for ensuring that a controlled chain reaction is maintained?
Correct Answer: \( \boxed{\mathrm{D}} \)
A nuclear reactor uses a moderator to slow down fast neutrons. Slower neutrons are more effective at producing further fission in many reactor fuels, helping the chain reaction to continue.
Control rods absorb neutrons and are inserted or withdrawn to control the rate of the chain reaction.
Therefore, moderators and control rods are the two components primarily responsible for maintaining a controlled chain reaction.
Shielding provides protection from radiation, while heat exchangers transfer thermal energy. These are important reactor components but do not primarily control the chain reaction.
Hence, the correct answer is \( \boxed{\mathrm{D}} \).
For a steady chain reaction, exactly 1 neutron per fission should cause another fission.
Total neutrons per fission = 4
Neutrons causing fission = 4 – \( N_c \) – \( N_1 \) = 1
So \( N_c + N_1 = 3 \)
Checking options:
(A) 1 + 1 = 2 ≠ 3
(B) 1 + 3 = 4 ≠ 3
(C) 2 + 1 = 3 ✓
(D) 2 + 2 = 4 ≠ 3
✅ Answer: (C)
