91. The group of solar cells joined together in a definite pattern is called a-
1. Battery
2. Solar Heater
3. Solar cooker
4. Solar cell panel
Option “4” is correct. Solar panels are those devices which are used to absorb the sun’s rays and convert them into electricity or heat. A solar panel is actually a collection of solar (or photovoltaic) cells.
92. The study of origin and evolution of universe is known as ________.
Option “1” is correct. Cosmology is the study of the origin, evolution of the universe.
93. If a ball is thrown up, which of the following does not change?
1. Acceleration due to gravity
2. Speed
3. Potential energy
4. Distance
Option “1” is correct. When a ball is thrown upwards the acceleration due to gravity remains constant throughout. It comes to rest for a moment at the highest point of motion just before returning back to earth.
94. The SI unit of intensity of sound is ______.
1. Watt per square meter
2. Joule per square meter
3. Newton per square meter
4. Tesla per square meter
Option “1” is correct. The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m2).
95. To keep drinks at the same temperature for quite sometime, the walls of thermos bottle are coated with:
Option “3” is correct. The glass or steel which is used in thermos bottle is coated with a silver layer to keep drinks at the same temperature for some time.
96. The atmosphere exerts enormous pressure on us. But, we do not feel it because-
1. Our blood exerts a pressure slightly more than that of the atmosphere
2. We are used to it
3. Our bones are very strong and can withstand the pressure
4. The surface are of our head is very small
Option “1” is correct. The atmosphere exerts enormous pressure on us but we do not feel it, because our blood exerts pressure slightly more than that of the atmosphere. We feel this pressure in water because the pressure underwater is greater than our normal blood pressure.
97. The sensation of weightlessness in a spacecraft in an orbit is due to the –
1. Absence of gravity outside
2. Acceleration in the orbit which is equal to the acceleration due to gravity outside
3. Presence of gravity outside but not inside the spacecraft
4. Fact that spacecraft in the orbit has no energy
Option “2” is correct. The sensation of weightlessness in a spacecraft in an orbit is due to the acceleration in the orbit which is equal to the acceleration due to gravity outside.
98. It is easier to carry two buckets of water in one hand each, than to carry only one in one hand because –
1. weight of buckets are balanced
2. centre of gravity falls within the body
3. centre of gravity and centre of equilibrium fall within the feet
4. resultant weight of buckets is zero
Option “3” is correct. It is easier to carry two buckets of water in one hand each, than to carry only one in one hand because centre of gravity and centre of equilibrium fall within the feet.
99. In a nuclear reactor, one of the following is used as a fuel?
1. Coal
2. Uranium
3. Radium
4. Diesel
Option “2” is correct. Uranium is used as fuel in nuclear reactors.
100. Tungsten is used for the manufacture of the filament of an electric bulb, because –
1. it is a good conductor
2. it is economical
3. it is malleable
4. it has a very high melting point
Option “4” is correct. Tungsten is used for the manufacture of the filament of an electric bulb due to its high melting point of 3422 °C.
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