Nuclear fission and nuclear fusion — practice questions

Question 1 · difficulty L1 · recall

Nuclear fission is the process in which

• A. light nuclei combine into a heavier one
• B. an electron splits into photons
• C. a heavy nucleus splits into lighter nuclei
• D. a nucleus absorbs light without changing

Question 2 · difficulty L1 · understanding

Nuclear fusion is the process in which

• A. a heavy nucleus splits
• B. gamma photons become electrons only
• C. atoms chemically bond
• D. light nuclei combine to form a heavier nucleus

Question 3 · difficulty L2 · understanding

A fission chain reaction is sustained by

• A. neutrons released in one fission causing further fissions
• B. electrons emitted from atoms causing chemical reactions
• C. visible photons alone
• D. gravity between nuclei

Question 4 · difficulty L2 · application

The Sun's energy is primarily produced by

• A. nuclear fission of uranium
• B. nuclear fusion
• C. chemical combustion
• D. radio waves heating its core

Question 5 · difficulty L3 · application

Why are extremely high temperatures needed for controlled fusion?

• A. To remove all neutrons
• B. To make electric charge vanish permanently
• C. To give nuclei enough kinetic energy to overcome strong Coulomb repulsion sufficiently for the nuclear force to act
• D. To reduce the speed of light

Question 6 · difficulty L3 · application

A moderator in a thermal fission reactor is used mainly to

• A. absorb all neutrons permanently
• B. increase fuel temperature only
• C. convert neutrons into electrons
• D. slow down neutrons

Question 7 · difficulty L4 · analysis

Control rods in a reactor regulate the chain reaction by

• A. absorbing neutrons
• B. producing extra neutrons
• C. reflecting all gamma rays
• D. increasing uranium mass number

Question 8 · difficulty L4 · analysis

Both fission of heavy nuclei and fusion of light nuclei can release energy because products move

• A. toward zero binding energy
• B. toward higher binding energy per nucleon
• C. toward larger total mass without energy change
• D. away from the binding-energy curve peak

Question 9 · difficulty L5 · analysis

A reactor has an effective multiplication factor exactly 1. The chain reaction is

• A. subcritical and dying out
• B. supercritical and growing exponentially
• C. critical and steady on average
• D. impossible

Question 10 · difficulty L5 · analysis

Which comparison is correct?

• A. Fusion requires no Coulomb barrier
• B. Fission is chemical burning
• C. Both processes conserve rest mass exactly with no energy release
• D. Fission can be initiated in suitable heavy nuclei by neutrons, while fusion requires light nuclei to approach extremely closely