GK - Physics
6.
Lightning is caused due to
Answer
Lightning is a discharge of electrical energy that builds up within a storm. The charges develop because a storm causes air to move around which rubs against itself to generate electrical charges. Eventually the charge increases to a point where the electricity can flow through the air. Once an electric discharge starts it provides a better path for more electrical flow than normal air due to ionization which results in a sudden, large and fast discharge.
Answer :
Option BExplanation :
Lightning is a discharge of electrical energy that builds up within a storm. The charges develop because a storm causes air to move around which rubs against itself to generate electrical charges. Eventually the charge increases to a point where the electricity can flow through the air. Once an electric discharge starts it provides a better path for more electrical flow than normal air due to ionization which results in a sudden, large and fast discharge.
7.
The working of a rocket is based on the principle of:
Answer
The operation of a rocket illustrates the conservation of momentum. Just before launching, the momentum of the rocket is zero. When the rocket is fired, it forces a jet of hot gases with a high velocity through the nozzle. The jet of gases acquires a momentum downwards. Hence, the rocket acquires a momentum of equal magnitude in opposite direction. Thus the rocket moves upwards.
Answer :
Option AExplanation :
The operation of a rocket illustrates the conservation of momentum. Just before launching, the momentum of the rocket is zero. When the rocket is fired, it forces a jet of hot gases with a high velocity through the nozzle. The jet of gases acquires a momentum downwards. Hence, the rocket acquires a momentum of equal magnitude in opposite direction. Thus the rocket moves upwards.
8.
Light travels at the fastest speed in
Answer
Because vacuum's refractive index is least.
Answer :
Option DExplanation :
Because vacuum's refractive index is least.
9.
On a cold day when a room temperature is 5°C, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 5°C, because
Answer
On a chilly day, the room temperature is lower than our body temperature. Since metals have a higher coefficient of thermal conductivity than plastic, they are better conductor of heat than plastic. So, when we touch the metal cap and the plastic body of a pen, heat from our fingers will flow to the metal cap much more quickly than to the plastic body.
Answer :
Option CExplanation :
On a chilly day, the room temperature is lower than our body temperature. Since metals have a higher coefficient of thermal conductivity than plastic, they are better conductor of heat than plastic. So, when we touch the metal cap and the plastic body of a pen, heat from our fingers will flow to the metal cap much more quickly than to the plastic body.
10.
A pond of water appears less deep due to
Answer
The apparent depth will look less that its real depth due to the refraction of light. Light rays from bottom of pool are bent away from the normal as they pass from water into the air. This makes the pool appear shallower than it really is.
Answer :
Option CExplanation :
The apparent depth will look less that its real depth due to the refraction of light. Light rays from bottom of pool are bent away from the normal as they pass from water into the air. This makes the pool appear shallower than it really is.
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