Physics – GK Questions

Ans: C

Explanation:Copper is an excellent conductor of electricity and is corrosion-resistant, making it ideal for use in lightning conductors. While aluminium and zinc can also conduct electricity, they are not as effective as copper. Iron is also a conductor, but it is prone to rusting, which can compromise its effectiveness.
Correct_Option:C

Ans: B

Explanation:The density of water is maximum at 4°C. While it’s often approximated as 1 g/cc at room temperature, the precise value of 1 g/cc is specifically valid at 4°C due to the anomalous expansion of water.
Correct_Option:B

Ans: A

Explanation:Black surfaces are good absorbers and emitters of radiation. Rough surfaces are generally better absorbers and emitters than smooth surfaces because they have a larger effective surface area for interaction with radiation. Therefore, a black and rough body will absorb heat most effectively.
Correct_Option:A

Ans: C

Explanation:An anemometer is a device used for measuring wind speed, which is the velocity of air in motion.
Correct_Option:C

Ans: B

Explanation:The formula relating Fahrenheit (F) and Celsius (C) is F = (9/5)C + 32. To find the temperature where both scales read the same, we set F = C. This gives us C = (9/5)C + 32. Subtracting C from both sides: 0 = (4/5)C + 32. Subtracting 32: -32 = (4/5)C. Multiplying by 5/4: C = -32 * (5/4) = -40. Therefore, -40° is the temperature where both scales are the same.
Correct_Option:B

Ans: C

Explanation:A mirage is an optical phenomenon that occurs due to the bending of light rays as they pass through layers of air with different temperatures and therefore different densities. This bending of light is called refraction. In certain conditions, particularly in hot environments, the air near the ground is significantly hotter and less dense than the air above it. Light traveling from a distant object (like the sky) towards the observer passes through these layers. As the light enters warmer, less dense air, it bends upwards away from the normal. When the angle of incidence becomes sufficiently large, the light can undergo total internal reflection, causing an image of the sky (which appears as a pool of water) to be seen by the observer. Therefore, both refraction and total internal reflection are essential for the formation of a mirage.
Correct_Option:C

Ans: A

Explanation:The kinetic energy (KE) of an object is given by the formula KE = 0.5 * m * v^2, where m is the mass of the object and v is its velocity. In this case, m = 10 kg and v = 2 m/s. Therefore, KE = 0.5 * 10 kg * (2 m/s)^2 = 0.5 * 10 * 4 J = 20 J.
Correct_Option:A

Ans: B

Explanation:Surface tension is the tendency of liquid surfaces to shrink into the minimum surface area possible. Oil spreads on water because water has a significantly higher surface tension than oil. This means water molecules are more strongly attracted to each other than oil molecules are to water molecules, causing the oil to spread out to reduce its contact with the water.
Correct_Option:B

Ans: B

Explanation:Microwaves are electromagnetic waves. The frequency of 3 cm microwaves is approximately 10 GHz (10^10 Hz). The period of oscillation (T) is the reciprocal of the frequency (f), so T = 1/f. Therefore, T = 1 / (10 x 10^9 Hz) = 1 x 10^-10 seconds.
Correct_Option:B

Ans: B

Explanation:Siemens (symbol S) is the SI derived unit of electrical conductance. Conductance is the reciprocal of resistance. Electric potential is measured in volts, magnetic flux in webers, and refractive index is a dimensionless quantity.
Correct_Option:B

Ans: A

Explanation:A quartz crystal exhibits the piezoelectric effect, meaning it generates an electric charge when subjected to mechanical stress and, conversely, deforms mechanically when an electric field is applied. In a quartz watch, an electric current causes the crystal to vibrate at a very precise frequency, which is then used to keep time. The Edison effect relates to thermionic emission, the photoelectric effect involves the emission of electrons when light strikes a material, and the Johnson effect is related to thermal noise in conductors.
Correct_Option:A

Ans: A

Explanation:Heavy water (deuterium oxide, $D_2O$) is used as a neutron moderator in nuclear reactors. Its primary role is to slow down fast neutrons, making them thermal neutrons, which are more likely to cause fission in uranium-235. This process is crucial for sustaining a nuclear chain reaction. It is not used to absorb neutrons or to directly increase temperature, nor does it increase the speed of neutrons; rather, it decreases their kinetic energy.
Correct_Option:A

Ans: D

Explanation:Polarisation is the phenomenon that demonstrates the transverse nature of light. In transverse waves, the oscillations are perpendicular to the direction of wave propagation. Polarisation selectively filters these oscillations, allowing only those in a specific direction to pass through. This selective filtering is only possible if the light waves are oscillating perpendicular to their direction of travel, which is the defining characteristic of transverse waves. Reflection, interference, and diffraction can occur for both transverse and longitudinal waves, and do not specifically prove the transverse nature of light on their own.
Correct_Option:D

Ans: D

Explanation:Good conductors of electricity allow electric current to flow through them easily. Dry air, paper, and kerosene are all electrical insulators, meaning they resist the flow of electricity. Graphite, a form of carbon, has free electrons that can move and carry an electric charge, making it a good conductor.
Correct_Option:D

Ans: C

Explanation: Tsunamis are typically caused by large underwater earthquakes that displace the seabed. This displacement pushes a massive amount of water upwards, creating waves that travel across the ocean. Options A and B are incorrect because they describe forces or weather patterns not directly related to tsunami generation. Option D is incorrect as monsoon winds can cause large waves but not the devastating scale of a tsunami.
Correct_Option:C

Ans: D

Explanation:A black body is an idealized object that absorbs all incident electromagnetic radiation, regardless of frequency or wavelength.
Correct_Option:D

Ans: B

Explanation:A fountain pen works by the principle of capillary action. The ink in the reservoir flows down into the nib due to gravity, but the fine channels in the nib and feed are designed to draw the ink up and out of the reservoir towards the writing surface. This upward movement against gravity, and the even flow of ink, is facilitated by capillary action, which is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity.
Correct_Option:B

Ans: B

Explanation:A gas thermometer is more sensitive than a liquid thermometer because gases expand much more significantly than liquids for a given change in temperature. This larger expansion makes the change in volume (and therefore pressure, in a constant volume gas thermometer) more noticeable and easier to measure, leading to higher sensitivity.
Correct_Option:B

Ans: C

Explanation:A mirage is an optical phenomenon that occurs when light rays are bent due to variations in air density caused by temperature differences. These temperature differences arise from the unequal heating of the Earth’s surface and the atmosphere. Hot surfaces heat the air above them more than cooler surfaces, creating layers of air with different densities and refractive indices. Light bends as it passes through these layers, creating the illusion of water or inverted images.
Correct_Option:C

Ans: D

Explanation:Kinetic energy is the energy an object possesses due to its motion. The formula for kinetic energy is KE = 1/2 * mv^2, where ‘m’ represents the mass of the object and ‘v’ represents its velocity (or speed). Therefore, kinetic energy depends on both the mass and the velocity of the moving body.
Correct_Option:D