Science Test - Class 10 - Class 10 MCQ

The magnification of plane mirror is 1 since the size of the image is the same as the size of the object. The distance of the image from the mirror is the same as the distance of the object from the mirror. 

The experiment may be performed on the same wall as the window to obtain a sharp image since a concave mirror mostly forms images on the same side as that of the object. The object and the image are on the same side of the concave mirror, except when the object is placed between the pole and the focus.

Metals are electropositive in nature and are therefore, good conductors of electricity. Quartz is a chemical compound consisting of one part silicon and two parts oxygen (SiO₂). It is the most abundant mineral found in Earth's surface. Its unique properties make it one of the most useful natural substances. It has electrical properties and heat resistance that make it valuable in electronic products. Mica has superior electrical properties as an insulator. Rubber is also an insulator.

Manganin is an alloy of copper, manganese and nickel. It typically contains 86% copper, 12% manganese, and 2% nickel. It was first developed by Edward Weston in 1892 improving upon his Constantan. Manganin wire is used in the manufacture of resistors.

The far point  is  infinity  for  normal  eye.  It  is  the farthest  point  upto which  the  eye  can see object clearly.

Scleroid: It is the outermost part of the eye. It protects the inner delicate parts of the eye.

Cornea:  It  is  a  thin membrane  through which  light  enters.  It  forms  the transparent bulge on the front of eyeball.

Iris:  It  is a dark muscular diaphragm  that controls  the size of pupil.  It  is behind  the cornea and gives colour to the eye.

Crystalline eye  lens: It is composed of a fibrous, jelly like material. This is double convex  lens  that converges  light at  retina

When ray of light enters from a rarer medium (air) into a denser medium (water), it bends towards normal at the point of incidence.

 Momentum is a vector quantity. A vector quantity possesses both a magnitude and direction. Since mass is a scalar quantity and velocity is a vector quantity, we can derive that momentum must therefore be a vector quantity as the product of a vector with a scalar is a vector. 

1- A because dynamo works on the principle of electromagnetism.
2-C, because the area around which a magnet's magnetism is experienced is called magnetic field or magnetism.
3-B, the device which converts mechanical energy into electrical energy is electric generator.
4-D Andre Marie ampere discovered current and after her name i.e ampere is given.

The human body is an electromagnetic organism. In human body, small electric currents travels along the nerve cells due to ions, same way as electricity flows through an electric wire. This current produces a very weak magnetic field in the human body. Heart and brain are the two main organs in the human body where this magnetic field is quite significant. 

To match the given options with the correct response, we need to understand the concepts mentioned in each option.
1. Appliances with exposed metal parts always need:
- This refers to the safety feature of electrical appliances that have exposed metal parts.
- Exposed metal parts of appliances need to be grounded for safety purposes.
- The correct response for this option is B - Three pin plug, as a three-pin plug provides grounding.
2. The unidirectional current flow in the circuit:
- Unidirectional current flow refers to the flow of current in a single direction without changing its direction.
- This type of current is known as Direct Current (D.C.).
- The correct response for this option is A - D.C.
3. The current which changes its direction at regular intervals:
- Current that changes its direction at regular intervals is known as Alternating Current (A.C.).
- Most household electrical appliances use A.C. as it is more suitable for transmission and distribution.
- The correct response for this option is C - A.C.
4. Device that makes use of the fact that magnetism in presence of electricity produces motion:
- This device utilizes the interaction between electricity and magnetism to produce motion.
- It is known as an electric motor, which converts electrical energy into mechanical energy.
- The correct response for this option is B - Electric Motor.
Based on the explanations above, the correct match between the options and their responses is:
Option B:
- 1-D, 2-A, 3-C, 4-B
Therefore, option B is the correct answer.

Statement: 'An electric current always produces a magnetic field'
Explanation:
To determine the correctness of the statement, we need to understand the relationship between electric current and magnetic fields.
1. Relationship between Electric Current and Magnetic Fields:
- When an electric current flows through a wire, it generates a magnetic field around it.
- The strength of the magnetic field depends on the magnitude of the current. Higher the current, stronger the magnetic field.
- The magnetic field is created in concentric circles around the wire, with the wire being the axis of symmetry.
- The direction of the magnetic field can be determined using the right-hand rule, where the thumb points in the direction of the current flow and the curled fingers represent the magnetic field lines.
2. Exceptions to the Statement:
While the statement is generally true, there are some exceptions where an electric current does not produce a magnetic field. These exceptions include:
- When the electric current is static or at rest, there is no magnetic field produced.
- In certain conductors, such as superconductors, the electric current can flow without any resistance and therefore does not produce a magnetic field.
Conclusion:
Considering the relationship between electric current and magnetic fields, we can conclude that the statement 'An electric current always produces a magnetic field' is partially true. While it is generally true, there are exceptions where an electric current does not produce a magnetic field.

All given options are non conventional source of energy.

Suffocation and headache can be caused by carbon monoxide, Green house effect is due to Carbon dioxide, Acid rains are due to sulphur dioxide and smog is as a result of Nitrogen dioxide.

A uranium-235 atom absorbs a neutron and fissions into two new atoms (fission fragments), releasing three new neutrons and some binding energy. 

(1) The group of solar cells joined together in definite pattern is solar panel---Solar panels are those devices which are used to absorb the sun's rays and convert them into electricity or heat. Description: A solar panel is actually a collection of solar (or photovoltaic) cells, which can be used to generate electricity through photovoltaic effect
(2) The device used for obtaining energy for flowing water is water wheel----A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill
(3) A barrier constructed on the river to store the flowing water is dam---A dam is usually constructed across a river to create a reservoir in the valley behind by storing the water that flows into it naturally. ... Small rivers and streams are usually diverted through a tunnel, or a channel that is constructed around the side of the dam
(4) A domestic fuel which contains butane is LPG---Liquefied petroleum gas or liquid petroleum gas (LPG or LP gas), also referred to as simply propane or butane, are flammable mixtures of hydrocarbon gases

Solar heater works with the help of sunlight but on a Cloudy day there is no sunlight on earth as result of which solar heater will not work .

Ozone layer is important because it prevents too many harmful ultra violet rays from reaching earth. Ultra violet rays have the capability to destroy plants and animals and can cause skin cancer, cataracts to human beings. Existence of life on earth is possible only because of the presence of ozone layer around the earth

A khadin, also called a dhora, is an ingenious construction designed to harvest surface runoff water for agriculture. Its main feature is a very long (100-300 m) earthen embankment built across the lower hill slopes lying below gravelly uplands. Sluices and spillways allow excess water to drain off. The khadin system is based on the principle of harvesting rainwater on farmland and subsequent use of this water-saturated land for crop production.
First designed by the Paliwal Brahmins of Jaisalmer, western Rajasthan in the 15th century, this system has great similarity with the irrigation methods of the people of Ur (present Iraq) around 4500 BC and later of the Nabateans in the Middle East. A similar system is also reported to have been practised 4,000 years ago in the Negev desert, and in southwestern Colorado 500 years ago.

The burning of fossils fuels produces lots of CO₂ that is one of the major green house gas. This has resulted in the increase in temperature on the earth called Global warming.

Hydrogen molecules violently react with oxygen when the existing molecular bonds break and new bonds are formed between oxygen and hydrogen atoms. As the products of the reaction are at a lower energy level than the reactants, the result is an explosive release of energy and the production of water

oxidation is loss of electron and reduction is gain of electrons 

Reducing agent is itself oxidized and oxidizing agent is itself reduced so  reducing agent electron losing species and oxidizing one is electron gaining species

Mg gets oxidised by reacting with O₂ to form MgO

Opposite to combination reaction means then the reaction should be decomposition reaction
Decomposition reaction: A reaction in which a single large compound splits into small compounds
AB--->A+B

Here decomposition reaction is taking place in i and ii options

Incandescent light bulbs consist of an air-tight glass enclosure (the envelope, or bulb) with a filament of tungsten wire inside the bulb, through which an electric current is passed.

Pyrolusite is a mineral consisting essentially of manganese dioxide (MnO₂). It is an important ore of manganese. It is a black, amorphous mineral, often with a granular, fibrous or columnar structure.

Highly reactive metals like Potassium, Sodium (Na), Calcium (Ca), Aluminium and Magnesium are obtained by electrolysis of their chlorides in molten state. They cannot be extracted by reducing their oxides with carbon. Iron (Fe) can be obtained from its oxide ore by reduction with coke or aluminium powder. Copper (Cu) can be obtained by heating its sulphide ore in air.

Platinum (Pt), Gold (Au) and Silver (Ag) occur in their free or native state.

The halogens are located on the left of the noble gases on the periodic table. These five toxic, non-metallic elements make up Group 17 of the periodic table and consist of: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Although astatine is radioactive and only has short-lived isotopes, it behaves similar to iodine and is often included in the halogen group. Because the halogen elements have seven valence electrons, they only require one additional electron to form a full octet. This characteristic makes them more reactive than other non-metal groups.

Brass gets discolored in air because of the presence of Hydrogen sulphide

It is because the presence of mixture of hydrogen and sulphide and brass is a type of thing which has a color very light and mixture is non temperature (hot and cold type of temperature) so it gets discolored.