Physics MCQs

Notes:
Pitch is a perceptual property that allows the ordering of sounds on a frequency-related scale. Pitch may be quantified as a frequency, but pitch is not a purely objective physical property; it is a subjective psycho-acoustical attribute of sound. When the frequency is high, the wavelength of the sound is shorter.

Notes:
The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius. The specific heat of water is 1 calorie/gram°C = 4.186 joule/gram°C which is higher than any other common substance. As a result, water plays a very important role in temperature regulation to be used in hot water bags.

Notes:
Hydroelectric power is a source of renewable energy. The kinetic energy of water falling from dam is used for rotating the turbines to rotate the armateur in generator producing electricity.

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Sunlight is converted into electricity using photovoltaic cell (PV). A photovoltaic system employs solar panels composed of a number of solar cells to supply usable solar power. Each solar cell consists of water of semiconductors like silicon or germanium.

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Wavelength is defined as distance between two consecutive crest or troughs. Between two crests, there is a trough exactly in the middle of the two crests. Distance between crest and adjacent trough will be half of the distance between two crests or simply, half of the wavelength.

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The phenomenon of raising outer edge of the curved road above the inner edge is to provide necessary centripetal force to the vehiclesto take a safer turn and the curved road is called Banking of Roads. If a car is on a level (unbanked) surface, the forces acting on the car are its weight, mg, pulling the car downward, and the normal force, N, due to the road, which pushes the car upward. Both of these forces act in the vertical direction and have no horizontal component. If there is no friction, there is no force that can supply the centripetal force required to make the car move in a circular path – there is no way that the car can turn.

Notes:
The sky appears blue because the molecules in the air scatter light in the higher wavelengths (that is, the blue light), while lower wavelength light (that is, the light on the red end of the spectrum) goes through to the ground. So the light that get finally reflected down from the scattering is blue, therefore a blue sky. This is called Rayleigh scattering. Rayleigh scattering, is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light.

Notes:
In photography, shutter speed or exposure time is the effective length of time a camera’s shutter is open to let light enter into camera . The total exposure is proportional to this exposure time, or duration of light reaching the film or image sensor. The correct exposure for a particular object depends on the brightness of the object to be photographed.

Notes:
Graphite is a good conductor of electricity because its electrons are delocalized or free to move around. Each carbon atom in graphite is directly linked to only three carbon atoms through covalent bonds. Therefore, out of the four valence electrons in a carbon atom, only three are used for bonding and the fourth is relatively free. It can move easily from one carbon atom to the other.

Notes:
This coil of wire in an electric room heater or electric cooking heater is called an element. When these appliances are switched on after connecting to the electric supply, their elements become red hot and give out heat. The amount of heat produced in a wire depends on its material, length and thickness.