A neutron in a nuclear reactor collides head on elastically with the nucleus of a carbon atom initially at rest. The fraction of kinetic energy transferred from the neutron to the carbon atom is

• $\frac{11}{12}$

• $\frac{2}{11}$

• $\frac{48}{121}$

• $\frac{48}{169}$

Assertion: Thermonuclear fusion reactions may become the source of unlimited power for the mankind.

Reason: A single fusion event involving isotopes of hydrogen produces more energy from nuclear fission of  ${}_{93}{}^{235}\mathrm{U}$

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

An atom of mass number 15 and atomic number 7 captures an a-particle and then emits a proton. The mass number and atomic number of the resulting atom will be respectively

• 14 and 12

• 15 and 3

• 16 and 4

• 18 and 8

A zener diode is specified as having a breakdown voltage of 9.1 V, with a maximum power dissipation of 364 mW. What is the maximum current the diode can handle?

• 40 mA

• 60 mA

• 50 mA

• 45 mA

Assertion: Generally heavy nuclei are unstable.

Reason: It has more neutrons and protons.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false

The half-life of radium is 1600 years. What is the fraction of sample undecayed after 6400 years?

• $\frac{1}{16}$

• $\frac{1}{4}$

• $\frac{1}{8}$

• $\frac{1}{24}$

Mutual inductance of two coils can be increased by

• decreasing the number of turns in the coils

• increasing the number of turns in the coils

• winding the coils on wooden cores

• None of these

Assertion:  If a heavy nucleus is split into two medium-sized parts, each of the nuclei will have more binding energy per nucleon than the original nucleus. 

Reason:  Joining two light nuclei together to give a single nucleus of medium size means more binding energy per nucleon than the two nucleus.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false.

• If both assertion and reason are false.

79.

n-alpha particles per second are emitted from N atoms of a radioactive element. The half-life of the radioactive element is

• $\frac{\mathrm{n}}{\mathrm{N}} \mathrm{s}$

• $\frac{\mathrm{N}}{\mathrm{n}}\mathrm{s}$

• $\frac{0.693 \mathrm{N}}{\mathrm{n}} \mathrm{s}$

• $\frac{0.693 \mathrm{n}}{\mathrm{N}} \mathrm{s}$

Assertion:  The ratio for time taken for light emission from an atom to that for release of nuclear energy in fission is 1 : 100. 

Reason:  Time taken for the light emission from an atom is of the order of 10^-8 s.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.