General Science GK Questions with Answers – Page 5

Friction is a non-conservative force because the work it does depends on the path taken and the energy it removes is lost as heat.

A microphone is a transducer that changes the pressure variations of sound into a matching electrical signal. In a common dynamic microphone, sound waves make a thin diaphragm vibrate.

Light slows down when it enters water from air, so a ray that strikes the surface at an angle bends towards the normal.

A light year is the distance that light travels in empty space in one year, so despite the word "year" it measures length, not time.

A desiccant is a substance that absorbs moisture from its surroundings and keeps things dry, and silica gel is the most widely used one.

A plane mirror always forms an upright image of the same size as the object, and the image cannot be caught on a screen.

By the conservation of momentum, the pistol moves back with 3 m s⁻¹, and the minus sign shows it moves opposite to the bullet.

Silver is less dense, so a silver piece takes up more volume, loses more weight to buoyancy in water, and must therefore be heavier in air to show the same weight under water.

Silver reacts with traces of hydrogen sulphide in the air and forms a black coating of silver sulphide. This slow attack on a metal by its surroundings is called corrosion, and on silver it is usually called tarnishing.

In uniform circular motion the acceleration points towards the centre of the circle, at right angles to the velocity. In uniform circular motion the speed stays the same, but the direction of motion changes at every point, so the velocity keeps changing and the body is accelerating.

Villi are tiny finger-like folds of the inner lining of the small intestine that greatly increase its surface for absorbing digested food.

Zinc oxide is amphoteric: it reacts with acids as a base and with strong alkalis as an acid, giving a salt and water in both cases.

Slaked lime on the wall slowly absorbs carbon dioxide from the air and turns into a thin, shiny layer of calcium carbonate.

The ABO system sorts blood by the antigens present on the surface of red blood cells, and it has exactly these four groups.

Seen from the east end, the current flows away from the observer, and by the right-hand thumb rule the field lines around it are clockwise circles in a plane perpendicular to the wire.

When an object is weighed under water, the water pushes up on it with a buoyant force, so it seems lighter than in air; this reduced reading is its apparent weight.

Bleaching powder is calcium oxychloride, CaOCl₂, and DDT is dichlorodiphenyltrichloroethane; chlorine is the one element common to both. Bleaching powder is made by passing chlorine gas over dry slaked lime.

The more a colour is slowed by glass, the higher the refractive index for it and the more it bends.

The filament of an incandescent bulb must glow white-hot without melting, and tungsten has the highest melting point of all metals, about 3,400 °C. An incandescent bulb works by the heating effect of electric current: the thin coiled filament gets so hot, around 2,500 °C or more, that it gives…

In a given medium under the same conditions, sounds of all frequencies travel at the same speed; the speed depends on the medium, not on the pitch.