Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
1. When a tubelight breaks, a cracking sound is produced because ____?
[A] Pressure inside the lamp is less than atmospheric pressure
[B] Pressure inside the lamp is more than atmospheric pressure
[C] The lamp is filled with reactive gases
[D] The lamp is filled with mercury vapour
Show Answer
Correct Answer: A [Pressure inside the lamp is less than atmospheric pressure ]
Notes:
A fluorescent lamp tube is filled with a gas containing low pressure mercury vapor and argon, xenon, neon, or krypton. The pressure inside the lamp is around 0.3% of atmospheric pressure.
2. Ohm is a unit of measuring _________?
[A] Resistance
[B] Voltage
[C] Current
[D] None of the above
Show Answer
Correct Answer: A [Resistance]
Notes:
The ohm is the SI unit of electrical resistance. Electrical resistance of an object is the measure of its obstruction to the flow of electric current. It mainly depends on the material it is made of, cross sectional area of a conductor, length and temperature. The resistance of a conductor of unit cross-sectional area and unit length is known as Resistivity. The unit of resistivity is ohm-metre.
3. The speed of Sound is maximum in which of the following ?
[A] Air at zero degree C
[B] Air at 100 degree C
[C] Water
[D] Same in all
Show Answer
Correct Answer: C [Water]
Notes:The speed of sound in a medium is determined by the properties of that medium, primarily its density and elasticity. The speed of sound is fastest in solids, followed by liquids, and then gases. Let’s analyze the given options:
[A] Air at zero degrees Celsius: The speed of sound in air increases with temperature. At lower temperatures, the molecules in the air have less kinetic energy, which results in a slower speed of sound. So, the speed of sound in air at 0°C is slower compared to higher temperatures.
[B] Air at 100 degrees Celsius: As mentioned earlier, the speed of sound in air increases with temperature. So, the speed of sound in air at 100°C would be faster than at 0°C but still slower than in a solid or liquid.
[C] Water: The speed of sound in water is significantly faster than in air. Water is denser and more elastic than air, which allows sound waves to travel through it more quickly.
[D] same in all: This statement is not correct. The speed of sound varies depending on the medium. It is not constant and is definitely not maximum everywhere.
So, among the given options, the maximum speed of sound would be in “Water” (Option C).
4. What is the normal temperature of human being on Kelvin scale?
[A] 290
[B] 300
[C] 310
[D] 320
Show Answer
Correct Answer: C [310]
Notes:
The normal temperature for a human body is 310 kelvins is 36.85 degrees Celsius. The average normal body temperature is generally accepted as 98.6°F.
5. Which among the following is the most acceptable range of LEO (Low Earth orbit)?
[A] 350 – 2,600 kms
[B] 200-2000 kms
[C] 160 – 2,000 kms
[D] 160-1600 kms
Show Answer
Correct Answer: C [160 – 2,000 kms]
Notes:
This range is commonly used and accepted in the context of satellite orbits within the Earth’s atmosphere. It extends from approximately 160 kilometers (the Kármán line, which is often used as the boundary of space) to around 2,000 kilometers above the Earth’s surface.
6. Which among the following strictly works on the principle of dipole movement of the water molecules?
[A] Refrigerator
[B] Microwave Oven
[C] Air Conditioner
[D] Electric Geyser
Show Answer
Correct Answer: B [Microwave Oven]
Notes:
Microwave Oven strictly works on the principle of dipole movement of water molecule. A microwave oven is an electric oven that heats and cooks food by exposing it to electromagnetic radiation in the microwave frequency range.
7. Which among the following waves are used in the gemstone industry to change white topaz into blue topaz?
[A] X-Rays
[B] Gamma Rays
[C] Alpha Radiation
[D] Beta Radiation
Show Answer
Correct Answer: B [Gamma Rays]
Notes:
Gamma rays is commonly used in gemstone industry to change white topaz into blue topaz. Because white topaz is heat-treated to turn into blue topaz, the value of blue topaz is often decreased.
8. “Fermi” is a unit of which among the following?
[A] Mass
[B] Length
[C] Velocity
[D] Frequency
Show Answer
Correct Answer: B [Length]
Notes:
“Fermi” is the unit of length. The femtometre is an SI unit of length equal to 10⁻¹⁵ metres, which means a quadrillionth of one.
9. If the distance between the earth and the sun becomes one-fourth of what it is now, the gravitational force exerted on the earth by the sun would be:
[A] One-fourth of what it is now
[B] One-sixteenth of what it is now
[C] Sixteen times of what it is now
[D] Four times of what it is now
Show Answer
Correct Answer: C [ Sixteen times of what it is now]
Notes:
Gravitational force is inversely proportional to the square of the distance between the bodies.
10. The recoiling of gun is an example of which of the following?
[A] Law of Conservation of Angular Momentum
[B] Law of Conservation of Linear Momentum
[C] Conversion of Kinetic Energy to Potential Energy
[D] Law of Conservation of Energy
Show Answer
Correct Answer: B [Law of Conservation of Linear Momentum]
Notes:
The recoiling of gun is an example of Law of Conservation of Linear Momentum. When gun fires a bullet, it experiences a force in forward direction (action) , as a result the gun exerts a backward force (reaction) on the shoulder. Thus, it is in accordance with Law of Conservation of Linear Momentum which is also the Newton’s 3rd law of motion.
