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ChemistryClass 10CBSE

What is a neutralisation reaction? Give an example.

A neutralisation reaction occurs when an acid and a base react to produce a salt and water.General Formula: Acid + Base → Salt + WaterAlways exothermic heat is released.Example: HCl + NaOH → NaCl + H₂OApplications: Antacids treat heartburn; lime treats acidic soil; baking soda treats insect stings.A neutralisation reaction between an acid

ChemistryClass 10CBSE

What is a chemical change? Give examples.

A chemical change produces new substances with properties entirely different from the originals, and is generally irreversible.Indicators:Change in colour, evolution of gas, formation of precipitate, temperature change, change in smell.Examples:Burning of wood → ash and smoke (irreversible)<li data-list-i

ChemistryClass 10CBSE

What is molecular mass, and how is it calculated?

Molecular mass is the sum of the atomic masses of all atoms in one molecule of a substance, expressed in atomic mass units (u) or g/mol.Example: Water (H₂O):ElementNo. of AtomsAtomic MassTotalH212O11616Molecular Mass18 u&nb

ChemistryClass 10CBSE

What is atomic number?

The atomic number is the number of protons present in the nucleus of an atom.Symbol: ZUniquely identifies every element no two elements share the same atomic number.In a neutral atom, atomic number also equals the number of electrons.<li data-list-item-id="e6eb3735eea38d447f36b6730dba

ChemistryClass 10CBSE

What is the charge on a sulphide ion, S²⁻?

The charge on a sulphide ion is 2− (negative two).Sulphur (S) is in Group 16 and has 6 valence electrons.To achieve a stable octet, it gains 2 electrons, adding 2− charge: S²⁻.Examples:FeS: Fe²⁺ + S²⁻ → FeS<li data-list-item-id="e9d75261e2ac3fe13d

ChemistryClass 10CBSE

What is the valency of fluorine in calcium fluoride, CaF₂?

The valency of fluorine in CaF₂ is 1.Fluorine (F) belongs to Group 17 (halogens) and has 7 valence electrons.Needs 1 electron to complete its octet — forms one bond → valency of 1.In CaF₂: Calcium has valency 2, so bonds with two fluorine atoms (each valency 1).

ChemistryClass 10CBSE

Why does pure water always contain hydrogen and oxygen in a fixed ratio, regardless of its source?

Pure water always contains hydrogen and oxygen in the fixed ratio of 1:8 by mass (or 2:1 by number of atoms) because water is a compound, not a mixture.Elements in a compound are chemically bonded in a definite and fixed proportion this is the Law of Definite Proportions (Law of Constant Composition), stated by Joseph Proust.Every molecule o

ChemistryClass 10CBSE

What is the composition of misch metal?

Misch metal is an alloy of rare earth elements (lanthanides), primarily used in lighter flints and the steel industry.Composition:ComponentPercentageCerium (Ce)~50%Lanthanum (La)~25%Neodymium (Nd)~15%Other lanthanides + Iron~10%<li data-list-item-id="eff

ChemistryClass 10CBSE

What is an alloy? Give examples.

An alloy is a homogeneous mixture of two or more metals (or a metal and a non-metal) prepared to enhance desirable properties like strength, hardness, or corrosion resistance.Alloys are mixtures, not compounds their composition can vary.Made by melting metals together and cooling.Common Examples:<th

ChemistryClass 10CBSE

What is the mass of 10 moles of sodium sulphite, and how is it calculated?

The mass of 10 moles of sodium sulphite (Na₂SO₃) is 1260 g.Given:Formula: Na₂SO₃Number of moles = 10Molar Mass Calculation:ElementAtomsAtomic MassTotalNa22346S</

ChemistryClass 10CBSE

What is meant by a substance in chemistry?

A pure substance has a definite and uniform chemical composition and cannot be separated into simpler components by physical methods.Two types:Elements one kind of atom (e.g., gold, oxygen)Compounds two or more elements in fixed ratio (e.g., water, salt)Pure SubstanceMix

PhysicsClass 10CBSE

What is Zener voltage?

Zener voltage (V_Z) is the specific reverse voltage at which a Zener diode begins conducting in the reverse direction while maintaining a nearly constant voltage.Below V_Z: diode blocks current.At/above V_Z: current flows freely in reverse, voltage stays constant at V_Z.This voltage-clamping behaviour = ideal voltage regulators.Common val

PhysicsClass 10CBSE

What is magnetic induction?

Magnetic induction (B) measures the strength of a magnetic field specifically, the force per unit current per unit length on a conductor in the field.Symbol: B | Unit: Tesla (T)Vector quantity.Formula: B = F / (IL)Earth's

PhysicsClass 10CBSE

What is electromagnetic induction?

Electromagnetic induction is the generation of EMF in a conductor when the magnetic flux through it changes. Discovered by Michael Faraday in 1831.Faraday's Law: EMF = −dΦ/dt (negative sign = Lenz's Law — induced current opposes change)Applications: Electric generators, transformers, electric motors, induction cooktops, microphones.Electromagnetic induction is the generation of EMF/current by a changing magnetic field the foundational pri

PhysicsClass 10CBSE

What are eddy currents? Write two applications.

Eddy currents are loops of electrical current induced within a conductor by a changing magnetic field (Faraday's Law), flowing in closed circular paths.Oppose the change causing them (Lenz's Law).Generate heat (core losses in transformers — minimised by laminating cores).Two Major Applications:<li data-list-item-id="e989e415d772

PhysicsClass 10CBSE

How do you calculate current through a 6-ohm resistor using Ohm's law?

Ohm's Law: I = V / RExample (V = 12 V, R = 6 Ω): I = 12 / 6 = 2 AIf V = 6 V: I = 6 / 6 = 1 AMemory aid (Ohm's Law triangle): [ V ] ------- I | R Cover the unknown to find the formula.Current through any resistor is found using I = V/R; for a 6-ohm resistor at 12 V, the current is 2 amperes.

PhysicsClass 10CBSE

What is an electric field?

An electric field is the region around a charged object where another charged object experiences a force.Formula: E = F/q (in N/C or V/m)Vector quantity — direction from + to − charges.Field lines drawn from + to −, never cross, perpendicular to conductor surface.For a point charge: E = kQ/r² (k = 9 × 10⁹ N m²/C²

PhysicsClass 10CBSE

What is an electric fuse and how does it work?

An electric fuse is a short piece of thin wire with a low melting point, connected in series to protect circuits from overcurrent.How it works:Normal conditions → current flows without significant heating.Excess current (short circuit/overload) → fuse wire heats rapidly.Wire

PhysicsClass 10CBSE

What is electromotive force?

EMF (ε) is the total energy supplied by a source per unit charge as it drives charge around a complete circuit.Unit: Volt (V) not a force, it is energy per charge.EMF = maximum terminal voltage when no current flows (open circuit).EMF vs. Terminal Voltage: Terminal Voltage = EMF − I × r (internal resistance)</

PhysicsClass 10CBSE

What is electric potential difference?

Electric potential difference (voltage) between two points is the work done per unit positive charge in moving it from one point to another.Formula: V = W/q or V_AB = V_A − V_BDrives current through a circuit.Measured by a voltmeter connected in parallel.1 Volt = 1

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