Physics Syllabus (JEE Main)
Q. What is the primary product of a nuclear fusion reaction in stars?
A.
Helium
B.
Hydrogen
C.
Carbon
D.
Uranium
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Solution
The primary product of nuclear fusion reactions in stars is helium, formed from the fusion of hydrogen nuclei.
Correct Answer: A — Helium
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Q. What is the primary product of nuclear fusion in stars like the Sun?
A.
Helium
B.
Hydrogen
C.
Carbon
D.
Oxygen
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Solution
The primary product of nuclear fusion in stars like the Sun is helium, formed from the fusion of hydrogen nuclei.
Correct Answer: A — Helium
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Q. What is the primary purpose of a demodulator in a communication system?
A.
To amplify the signal
B.
To convert the signal back to its original form
C.
To filter the noise
D.
To encode the signal
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Solution
A demodulator converts the modulated signal back to its original form.
Correct Answer: B — To convert the signal back to its original form
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Q. What is the primary purpose of a modulator in a communication system?
A.
To amplify the signal
B.
To convert digital signals to analog
C.
To filter noise
D.
To encode information
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Solution
A modulator converts digital signals to analog for transmission.
Correct Answer: B — To convert digital signals to analog
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Q. What is the primary purpose of modulation in communication systems?
A.
To increase the bandwidth of the signal
B.
To reduce noise in the signal
C.
To allow the transmission of signals over long distances
D.
To convert digital signals to analog signals
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Solution
Modulation allows signals to be transmitted over long distances by shifting the frequency of the signal to a higher range, making it suitable for transmission through various media.
Correct Answer: C — To allow the transmission of signals over long distances
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Q. What is the primary reason for the formation of droplets of water on a leaf?
A.
Cohesion
B.
Adhesion
C.
Surface tension
D.
Gravity
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Solution
The formation of droplets is primarily due to surface tension, which minimizes the surface area of the liquid.
Correct Answer: C — Surface tension
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Q. What is the primary reason for the increase in viscosity of a liquid with molecular weight?
A.
Increased intermolecular forces
B.
Decreased temperature
C.
Increased pressure
D.
Decreased density
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Solution
Higher molecular weight leads to increased intermolecular forces, resulting in higher viscosity.
Correct Answer: A — Increased intermolecular forces
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Q. What is the primary reason for the occurrence of diffraction in waves?
A.
Wave interference
B.
Wave reflection
C.
Wave refraction
D.
Wave nature of light
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Solution
Diffraction occurs due to the wave nature of light, allowing it to bend around obstacles and spread out.
Correct Answer: D — Wave nature of light
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Q. What is the primary reason for the occurrence of diffraction?
A.
The wave nature of light
B.
The particle nature of light
C.
The speed of light
D.
The frequency of light
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Solution
Diffraction occurs due to the wave nature of light, allowing it to bend around obstacles.
Correct Answer: A — The wave nature of light
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Q. What is the primary reason for the operation of an electric motor?
A.
Electromagnetic induction
B.
Lorentz force
C.
Coulomb's law
D.
Ohm's law
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Solution
Electric motors operate based on the Lorentz force, which acts on current-carrying conductors in a magnetic field, causing rotation.
Correct Answer: B — Lorentz force
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Q. What is the primary reason for the phenomenon of capillarity?
A.
Surface tension
B.
Viscosity
C.
Density
D.
Pressure
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Solution
Capillarity is primarily caused by surface tension, which allows liquids to rise or fall in narrow spaces against gravity.
Correct Answer: A — Surface tension
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Q. What is the primary reason for using insulation in buildings?
A.
To prevent conduction
B.
To enhance convection
C.
To increase radiation
D.
To allow heat flow
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Solution
Insulation is used primarily to prevent conduction of heat, thereby maintaining the desired temperature inside buildings.
Correct Answer: A — To prevent conduction
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Q. What is the primary type of decay for an unstable nucleus with too many protons?
A.
Alpha decay
B.
Beta decay
C.
Gamma decay
D.
Positron emission
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Solution
An unstable nucleus with too many protons typically undergoes alpha decay, where it emits an alpha particle (2 protons and 2 neutrons) to become more stable.
Correct Answer: A — Alpha decay
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Q. What is the primary type of radiation emitted by uranium-238?
A.
Alpha radiation
B.
Beta radiation
C.
Gamma radiation
D.
X-rays
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Solution
Uranium-238 primarily emits alpha radiation during its decay process.
Correct Answer: A — Alpha radiation
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Q. What is the primary type of radiation emitted during alpha decay?
A.
Helium nucleus
B.
Electron
C.
Photon
D.
Neutrino
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Solution
During alpha decay, an alpha particle, which is a helium nucleus (2 protons and 2 neutrons), is emitted.
Correct Answer: A — Helium nucleus
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Q. What is the primary use of a Wheatstone bridge in practical applications?
A.
To measure voltage
B.
To measure current
C.
To measure resistance
D.
To measure power
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Solution
The primary use of a Wheatstone bridge is to measure unknown resistances by balancing it against known resistances.
Correct Answer: C — To measure resistance
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Q. What is the primary use of nuclear fission in power plants?
A.
To produce nuclear weapons
B.
To generate heat for electricity
C.
To create isotopes for medical use
D.
To study nuclear reactions
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Solution
Nuclear fission is primarily used in power plants to generate heat, which is then converted into electricity.
Correct Answer: B — To generate heat for electricity
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Q. What is the primary use of nuclear fission?
A.
Medical imaging
B.
Nuclear power generation
C.
Smoke detectors
D.
Radiocarbon dating
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Solution
Nuclear fission is primarily used for nuclear power generation.
Correct Answer: B — Nuclear power generation
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Q. What is the primary use of nuclear reactors?
A.
To produce nuclear weapons
B.
To generate electricity
C.
To create isotopes for medical use
D.
To study nuclear physics
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Solution
The primary use of nuclear reactors is to generate electricity through controlled nuclear fission.
Correct Answer: B — To generate electricity
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Q. What is the primary use of polarizers in photography?
A.
To increase brightness
B.
To reduce glare
C.
To enhance colors
D.
To focus light
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Solution
Polarizers are primarily used in photography to reduce glare from reflective surfaces.
Correct Answer: B — To reduce glare
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Q. What is the primary use of radioactive isotopes in medicine?
A.
Energy production
B.
Diagnostic imaging
C.
Food preservation
D.
Industrial applications
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Solution
Radioactive isotopes are primarily used in medicine for diagnostic imaging and treatment.
Correct Answer: B — Diagnostic imaging
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Q. What is the principal quantum number for an electron in the 4th shell?
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Solution
The principal quantum number (n) corresponds to the shell number. For the 4th shell, n=4.
Correct Answer: D — 4
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Q. What is the principal quantum number of an electron in the 3p orbital?
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Solution
The principal quantum number (n) indicates the energy level of an electron. For a 3p orbital, n = 3.
Correct Answer: C — 3
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Q. What is the principal quantum number of an electron in the 4s orbital?
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Solution
The principal quantum number (n) indicates the energy level of an electron. For the 4s orbital, n = 4.
Correct Answer: C — 4
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Q. What is the principle behind a lever?
A.
Conservation of momentum
B.
Mechanical advantage
C.
Conservation of energy
D.
Centripetal force
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Solution
The principle behind a lever is mechanical advantage, which allows a smaller force to lift a larger load.
Correct Answer: B — Mechanical advantage
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Q. What is the principle behind a potentiometer?
A.
It measures current in a circuit
B.
It measures voltage by balancing it against a known voltage
C.
It measures resistance directly
D.
It measures power in a circuit
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Solution
A potentiometer measures voltage by balancing it against a known voltage, allowing for accurate voltage measurements without drawing current from the circuit.
Correct Answer: B — It measures voltage by balancing it against a known voltage
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Q. What is the principle behind a thermometer?
A.
Expansion of liquid with temperature
B.
Contraction of gas with temperature
C.
Change in color with temperature
D.
Change in pressure with temperature
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Solution
Thermometers work on the principle of expansion of liquid (like mercury) with temperature.
Correct Answer: A — Expansion of liquid with temperature
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Q. What is the principle behind Archimedes' principle?
A.
Buoyant force
B.
Pressure difference
C.
Surface tension
D.
Viscosity
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Solution
Archimedes' principle states that a body submerged in a fluid experiences a buoyant force equal to the weight of the fluid displaced.
Correct Answer: A — Buoyant force
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Q. What is the principle behind electromagnetic induction?
A.
Magnetic fields can create electric fields
B.
Electric fields can create magnetic fields
C.
Both A and B
D.
None of the above
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Solution
Electromagnetic induction is based on the principle that a changing magnetic field can induce an electric field and vice versa.
Correct Answer: C — Both A and B
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Q. What is the principle behind nuclear fission?
A.
Splitting of heavy nuclei
B.
Combining of light nuclei
C.
Emission of photons
D.
Absorption of neutrons
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Solution
Nuclear fission is the process where a heavy nucleus splits into two or more lighter nuclei, releasing energy.
Correct Answer: A — Splitting of heavy nuclei
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