Class 10 : Practice Questions and Answers

A plane mirror forms a virtual, upright image of the same size as the object. The image appears behind the mirror at the same distance as the object is in front.

A convex lens is used in magnifying glasses because it converges light and creates an enlarged image of the object being viewed.

The greenhouse effect is caused by increased carbon dioxide and other gases in the atmosphere, which trap heat from the Earth's surface.

In a parallel circuit, current divides among different branches, whereas in a series circuit, the same current flows throughout.

Light waves, being electromagnetic waves, can travel through a vacuum, unlike sound waves which require a medium to propagate.

The unit of electric charge is the Coulomb (C). One Coulomb is the amount of charge transferred by a current of one ampere in one second.

Ohm's law states that the voltage (V) across a conductor is directly proportional to the current (I) flowing through it, with resistance (R) as the constant. The formula is $V = IR$.

Electric power is calculated using Power = Voltage × Current. This shows how much energy is consumed or generated per unit of time in an electrical circuit.

Velocity is a vector quantity because it has both magnitude (speed) and direction. Speed has only magnitude and is a scalar quantity.

Refraction occurs when light passes from one medium to another, causing a change in speed, which results in the bending of light. It is most noticeable when light moves from air into water or glass.

The law of reflection states that the angle at which light strikes a surface (angle of incidence) equals the angle at which it reflects (angle of reflection). This principle explains how mirrors work.

Speed is the distance travelled per unit of time. The formula is Speed = Distance / Time.

The speed of sound in air at room temperature (about 20°C) is approximately 340 metres per second. This speed varies with temperature and the medium through which sound travels.

A decomposition reaction occurs when a compound breaks down into two or more simpler substances, represented as $AB \rightarrow A + B$.

Ethene is an unsaturated hydrocarbon because it contains a double bond between two carbon atoms, giving it fewer hydrogen atoms than saturated hydrocarbons.

Mercury is the only metal that remains liquid at room temperature. This unique property makes it useful in thermometers and other instruments.

Acetic acid is the main acid found in vinegar. It gives vinegar its characteristic sour taste and is widely used in cooking and as a preservative.

Ethanol is a versatile compound used as a fuel, a solvent in cleaning products, and as a food preservative.

Carbon dioxide is essential for photosynthesis. Plants use it along with water and sunlight to produce glucose and oxygen.

When zinc reacts with hydrochloric acid, hydrogen gas is released along with zinc chloride. This is a typical reaction of metals with acids.