Olympiad Test Level 1: Science and Technology - 2 - Class 4 MCQ

Optical scanner allows computer to use light as a source of input, hence it is an input device. Mouse is an input device as it sends information to the computer as per the User's requirements. Light pen is used as an input device which is used to draw or to point to any text.

Wilhelm Roentgen Invented X-Rays. He was trying to pass cathode rays through a glass, when he accidently invented X-rays.

Thomas Alva Edison invented the incandescent light bulb in 1879. It worked by passing electricity through a thin platinum filament in a glass vacuum bulb.

Bifocals were invented by Benjamin Franklin. These eyeglasses contain two optical powers to help see the objects at all distances. It is used by people who are both nearsighted and farsighted.

As seen here in the figure, the particles of solids are tightly packed in a regular pattern. Particles of liquid are less tightly packed as compared to solids and in gases, the particles are loosely packed with no regular pattern.

Matter is made up of tiny particles called atoms. Molecule is made up of two or more atoms. Elements are substance which cannot be broken down.

The state of matter with a fixed volume that can be compressed slightly is a liquid.  

Explanation: While solids have a fixed volume and cannot be easily compressed, liquids maintain a fixed volume but can be compressed slightly due to the closer spacing of their molecules compared to gases, which are highly compressible

Book is a solid as it has definite shape and volume. That means, it cannot flow, cannot be compressed.

Emile Berliner invented Gramophone. Gramophone is a record player. It used discs with grooves that were amplified by a needle.

When salt is added while boiling water, its boiling point increases; as it makes harder for the water molecules to escape from the utensil in which is boiled to enter into gas phase.

Tea leaves, Sugar, Cup are solids as they have fixed shape and volume. However, Tea and milk are liquid because they take up the space of the container in which they are kept.

Central Processing Unit(CPU) is called as the Brain of the computer, as all the programs are processed here and data is stored and output is send to the output devices.

Metals are called Lustrous, as they have shiny surfaces and they can be polished. For example: Gold, Silver, etc.

Monitor is an output device as it displays(output) the results of the user’s input on the screen.

Particles of solid are tightly packed. Particles of liquid are loosely packed as compared to solids and particles of gases are very loosely packed as compared to solids and liquids, therefore they are easily compressible.