Physics MCQs

Notes:
The layer of the atmosphere that reflects radio waves is the ionosphere. That is because there are gas particles in the ionosphere that are ionized.

Notes:
The electrostatic potential at any point in an electric field is defined as the work done in bringing a unit positive charge from infinity to that point against the electric force of the field. It is given by, V = W/q, where V is the potential, W is work done, and q the charge. Because work and charge both are scalar quantity, electrostatic potential is also a scalar quantity.

Notes:
Electric current is not a vector quantity. The other options – acceleration, force, and velocity – are all vector quantities that have both magnitude and direction. In contrast, electric current is a scalar quantity that has magnitude but no specific direction associated with it. Therefore, out of the choices provided, electric current is the one that is not a vector quantity.

Notes:
The number of waves or vibrations passing through a point in one second is called Frequency. The SI (System International) Unit of Frequency is Hertz(Hz). It is named for Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves.

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The rate of change of displacement of an object (displacement over elapsed time) is velocity. Velocity is a vector since it has both magnitude (called speed) and direction.

Notes:
Ice cover in lakes is seasonal and occurs where average daily temperature is below the freezing point. Once formed the lake ice thickens over the course of the winter as the temperature gets colder. The lakes thermal structure prepares for ice with 0°C water at the surface and denser 4°C at the bottom. Once meteorological conditions provide colder air, relative to warmer water, the water does not get colder – instead freezes into ice.

Notes:
The outside surface of a utensil used for heating is coated black so that it may absorb more heat and make heating quicker. This is because black surface is both a good absorber and emitter of heat.

Notes:
Telescope and Microscope are two scientific instruments that serve their purposes differently. One of the main differences between a telescope and a microscope is that a telescope is used to view things that are far whereas a microscope is used to view things that are very near. The other differences between telescope and microscope include : (i) The aperture (lens diameter) is larger in case of telescope than in microscope. (ii) Focal point in case of telescope is far off but in case of microscope, it is just a fraction of an inch. (iii) In telescope, focal length of objective lens is large and that of eye piece is small but in microscope, the objective less has small length and eyepiece has longer focal length.

Notes:
The tesla (symbol T) is the SI derived unit used to measure magnetic fields. Tesla can be measured in different ways; for example, one tesla is equal to one Weber per square metre. The tesla was first defined in 1960 by the General Conference on Weights and Measures (CGPM). It was named in honour of the physicist, electrical engineer, and inventor, Nikola Tesla.

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.