CBSE Class 10 Science Advanced Physics Source of Energy Nuclear Fission and Fusion MCQs Set 01

Answer: (d) all of the above

Explanation:
1. Solar cells turn sunlight into electricity.
2. Solar heaters and cookers turn it into heat.
3. Heat from the Sun drives winds and, through heat engines, mechanical work.
4. So the answer is (D), all of the above.

Teacher's Note:
1. When one option says all of the above, test each option separately first.
2. Sunlight can be converted into several forms.

Answer: (a) kinetic energy

Explanation:
1. Wind is air in motion.
2. Energy of a moving body is kinetic energy.
3. So the answer is (A).

Teacher's Note:
1. Link the word moving with kinetic.
2. A windmill turns because the moving air carries kinetic energy.

Answer: (c) electrical energy

Explanation:
1. A solar cell works by the photovoltaic effect.
2. Light falling on the semiconductor produces a potential difference.
3. So it gives electrical energy, option (C).

Teacher's Note:
1. Solar cells are also called photovoltaic cells.
2. They give d.c. electricity.

Answer: (c) CO₂ + CH₄ + H₂ + H₂S

Explanation:
1. Biogas forms by anaerobic degradation of dung.
2. It contains methane (main part), carbon dioxide, hydrogen and hydrogen sulphide.
3. This matches option (C).

Teacher's Note:
1. Remember methane is the major constituent.
2. Carbon monoxide is not present in biogas.

Answer: (b) non-conventional sources

Explanation:
1. Sources that nature keeps supplying are renewable.
2. Renewable sources are also called non-conventional sources.
3. So the answer is (B).

Teacher's Note:
1. Renewable = non-conventional; non-renewable = conventional.
2. Do not mix the two pairs.

Answer: (d) Petroleum

Explanation:
1. Wood, falling water and wind are renewable sources.
2. Petroleum is a fossil fuel and non-renewable.
3. So the odd one is (D).

Teacher's Note:
1. Group the options as renewable and non-renewable.
2. The odd one is whichever stands alone.

Answer: (c) methane

Explanation:
1. Sea weeds are biomass.
2. Biomass decays anaerobically to give biogas, whose main part is methane.
3. So the answer is (C).

Teacher's Note:
1. Think of sea weeds as plant waste (biomass).
2. Biomass gives biogas.

Answer: (d) all of the above

Explanation:
1. Ocean thermal energy (OTE), sea-wave energy and tidal energy are all obtained from the oceans.
2. So the answer is (D).

Teacher's Note:
1. Make a list of ocean energy forms.
2. All three listed are valid.

Answer: (d) Kerosene

Explanation:
1. Coke, coal and charcoal are solid fuels.
2. Kerosene is a liquid fuel obtained from petroleum.
3. So the answer is (D).

Teacher's Note:
1. Classify fuels by state: solid, liquid, gas.
2. Kerosene, petrol and diesel are liquids.

Answer: (c) 100°C to 140°C

Explanation:
1. A box-type solar cooker with a plane mirror gives moderate heating.
2. The temperature inside rises to about 100 °C to 130 °C (about 100 °C to 140 °C).
3. So the answer is (C).

Teacher's Note:
1. 300 °C and above needs a concave reflector.
2. Food can be cooked only above 100 °C or so.

Answer: (d) None of these

Explanation:
1. Water makes the steam but is not a fuel.
2. CO is a fuel gas but is not used in steam engines; CO2 does not burn.
3. The usual fuel is coal or wood, so it is none of these, option (D).

Teacher's Note:
1. Separate the working substance (water) from the fuel (coal).
2. CO2 cannot burn at all.

Answer: (a) primary fuel

Explanation:
1. A primary fuel is found in nature in the same form.
2. Wood is used as it is, so it is a primary fuel, option (A).

Teacher's Note:
1. Processed or secondary fuels (coke, coal gas) are made from primary fuels.
2. Wood is solid, not liquid.

Answer: (c) Natural gas

Explanation:
1. Fossil fuels are coal, petroleum and natural gas, formed from buried remains.
2. Coal gas, coke and producer gas are made from coal by processing, so they are secondary fuels.
3. So the answer is (C).

Teacher's Note:
1. Coal gas, coke and producer gas are made from coal.
2. Natural gas is a true fossil fuel.

Answer: (d) Secondary fuel

Explanation:
1. Gobar gas (biogas) is a gas made from dung by fermentation.
2. It is prepared from another material, so it is a secondary fuel, option (D).

Teacher's Note:
1. Primary fuels are used as found.
2. Gobar gas is obtained after processing dung.

Answer: (c) Calorific value

Explanation:
1. Methane (CH₄) has the largest share of hydrogen, and hydrogen gives the most heat per gram.
2. So methane has the highest calorific value (55 kJ/g) among hydrocarbons.
3. Its boiling point is the lowest and its carbon to hydrogen ratio the smallest, so (A), (B), (D) are wrong.
4. The answer is (C).

Teacher's Note:
1. Link high hydrogen content with high calorific value.
2. Compare hydrocarbons per gram of fuel.

Answer: (c) Nuclear reactor

Explanation:
1. A nuclear reactor allows a controlled chain reaction.
2. A thermopile measures heat radiation, a thermostat controls temperature, a cloud chamber shows particle tracks.
3. So the answer is (C).

Teacher's Note:
1. Control rods keep the fission rate steady.
2. Learn what each device does.

Answer: (c) Chadwick

Explanation:
1. James Chadwick discovered the neutron in 1932.
2. Rutherford found the nucleus and Millikan measured the electron charge.
3. So the answer is (C).

Teacher's Note:
1. Match each discovery with a name.
2. Chadwick means neutron.

Answer: (a) slowing neutrons

Explanation:
1. Slow neutrons are best at causing fission of uranium-235.
2. A moderator such as heavy water or graphite slows the fast neutrons.
3. So the answer is (A).

Teacher's Note:
1. Moderator slows; control rods absorb.
2. Do not say it stops neutrons.

Answer: (c) extremely high temperature

Explanation:
1. Nuclei must overcome their electrostatic repulsion.
2. This needs very large thermal energy, i.e. millions of kelvin.
3. So the answer is (C).

Teacher's Note:
1. This is why fusion is called a thermonuclear reaction.
2. Temperature is the key condition.

Answer: (c) A – Z

Explanation:
1. Mass number A = protons + neutrons.
2. Protons = Z, so neutrons = A – Z.
3. The answer is (C).

Teacher's Note:
1. Mass number counts nucleons.
2. Subtract protons to get neutrons.

Answer: (d) All of these

Explanation:
1. Total energy (including mass-energy), total charge and total momentum are all conserved in nuclear reactions.
2. So the answer is (D).

Teacher's Note:
1. Conservation laws hold in every nuclear reaction.
2. Mass-energy, not mass alone, is conserved.

Answer: (a) Alpha particles

Explanation:
1. Alpha particles are heavy and strongly ionising, so a sheet of paper stops them.
2. Beta particles go further and gamma rays go the furthest.
3. So the answer is (A).

Teacher's Note:
1. Order of penetration: alpha < beta < gamma.
2. More ionising means less penetrating.

Answer: (b) Neutron

Explanation:
1. Mass number: 235 + 1 = 236, and 141 + 92 = 233, so 3X has mass number 3.
2. Atomic number: 92 + 0 = 92 = 56 + 36, so X has charge 0.
3. Each X has mass number 1 and charge 0, so X is a neutron, option (B).

Teacher's Note:
1. Balance mass numbers and atomic numbers separately.
2. Fission of uranium releases 2 or 3 neutrons.

Answer: (b) 0.1%

Explanation:
1. Mass defect = 0.2134 u out of an initial mass of 236.0526 u.
2. Percentage = 0.2134 ÷ 236.0526 × 100 = 0.09%, about 0.1%.
3. So the answer is (B).

Teacher's Note:
1. The worked example on fission energy gives the same 0.09%.
2. Fission converts only a tiny part of the mass.

Answer: (c) Both renewable & non-renewable

Explanation:
1. Fusion fuel (hydrogen) is plentiful, so it is renewable.
2. Fission fuel (uranium) is limited, so it is non-renewable.
3. So nuclear energy is both, option (C).

Teacher's Note:
1. Split the answer between fission and fusion.
2. The chapter states it is partly renewable.

Answer: (b) n_e = n_p

Explanation:
1. A neutral atom has no net charge.
2. So the number of electrons equals the number of protons.
3. The answer is (B).

Teacher's Note:
1. Ions are the ones with unequal numbers.
2. Equal and opposite charges cancel.

Answer: (c) 15

Explanation:
1. A = Z + neutrons, so Z = 31 – 16 = 15.
2. The answer is (C), which is phosphorus.

Teacher's Note:
1. Use A = Z + N.
2. Check: 15 + 16 = 31.

Answer: (a) Mass number

Explanation:
1. Nucleons are protons plus neutrons.
2. Their total number is the mass number.
3. The answer is (A).

Teacher's Note:
1. Atomic number counts only protons.
2. Mass number counts all nucleons.

Answer: (d) Nucleus

Explanation:
1. The dense positively charged centre of an atom is the nucleus.
2. The answer is (D).

Teacher's Note:
1. Electrons move around it in orbits.
2. An ion is a charged atom.

Answer: (c) Heat and light both

Explanation:
1. Sunlight warms the earth (heat, from infrared) and lights it (visible light).
2. So the answer is (C).

Teacher's Note:
1. Remember the three parts of sunlight.
2. Both heat and light reach us.

Answer: (b) electrical energy.

Explanation:
1. In a thermal plant fuel burns to make steam.
2. The steam turns a turbine, which turns a generator.
3. So heat finally becomes electrical energy, option (B).

Teacher's Note:
1. Follow the chain: heat, mechanical, electrical.
2. The purpose of a power plant is electricity.

Answer: (b) 15 kmph.

Explanation:
1. A windmill needs a minimum average wind speed of about 15 km/h.
2. So the answer is (B).

Teacher's Note:
1. This is a fact to remember.
2. Slower winds cannot turn the blades usefully.

Answer: (a) Changing potential energy to kinetic energy of flowing (falling) water and then converting it to eletrical energy.

Explanation:
1. Water stored high has potential energy.
2. As it falls, this becomes kinetic energy, which turns the turbine and generator.
3. So the answer is (A).

Teacher's Note:
1. The chain is potential, kinetic, electrical.
2. Gravitational potential energy is the same as potential energy, so (C) is meaningless.

Answer: (a) They are acidic oxides and can cause acid rains.

Explanation:
1. Oxides of nitrogen and sulphur, and carbon dioxide, dissolve in water to form acids.
2. This gives acid rain and harms health and buildings.
3. The answer is (A).

Teacher's Note:
1. These gases do not cause noise.
2. Acid rain damages crops, water and monuments.

Answer: (b) nuclear energy

Explanation:
1. Bagasse, gobar gas and wood come from plants or animals.
2. Nuclear energy comes from nuclei, not from living matter.
3. The answer is (B).

Teacher's Note:
1. Biomass means living or recently living matter.
2. Bagasse is the fibre left from sugar cane.

Answer: (b) solar cells.

Explanation:
1. Solar cells are made from doped semiconductors such as silicon.
2. Furnaces, cookers and heaters work by reflecting and absorbing heat.
3. The answer is (B).

Teacher's Note:
1. Semiconductors turn light into electricity.
2. Cookers and heaters need mirrors and black surfaces.

Answer: (a) Wind Mills

Explanation:
1. Moving air turns the blades of a windmill.
2. The windmill then does work or drives a generator.
3. So the answer is (A).

Teacher's Note:
1. Generators and motors only convert; they do not catch the wind.
2. Windmills catch wind energy.

Answer: (a) ultra-violet

Explanation:
1. The ozone layer protects us from the Sun's harmful ultraviolet rays.
2. The answer is (A).

Teacher's Note:
1. Ozone absorbs UV, while carbon dioxide absorbs infrared.
2. That is why ozone depletion is dangerous.

Answer: (d) oxygen.

Explanation:
1. Biogas forms by anaerobic degradation.
2. Anaerobic means without oxygen, so the sealed digester has no oxygen.
3. The answer is (D).

Teacher's Note:
1. Anaerobic bacteria work without air.
2. Dung contains carbon, nitrogen and hydrogen.

Answer: (c) thermonuclear fusion reaction.

Explanation:
1. The hydrogen bomb releases energy by fusion of hydrogen isotopes.
2. Fusion needs very high temperature, so it is a thermonuclear fusion reaction.
3. The answer is (C).

Teacher's Note:
1. A fission bomb is the trigger only.
2. Fusion is not a chain reaction.