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PhysicsClass 12CBSE
How a Camera Flash Stores Energy for an Instant Burst of Light
See why the field inside a conductor is zero and where its charge sits, understand dielectrics and polarisation, derive the capacitance of a parallel plate capacitor with and without a dielectric, and combine capacitors in series and parallel and find the energy stored.
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Why Birds Can Sit Safely on a High-Voltage Wire
Define electric potential and potential difference and find the potential of a point charge, add potentials for a dipole and a system of charges, relate equipotential surfaces to the field, and calculate the potential energy of charges and of a dipole in a field.
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Why the Field Inside a Charged Metal Shell Is Exactly Zero
Calculate the electric flux of a uniform field through a surface, find the field of an electric dipole on its axial and equatorial lines, derive the torque on a dipole in a uniform field, and use Gauss's law for a line charge, a plane sheet and a spherical shell.
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Why Your Hair Stands Up After You Rub a Balloon on It
Learn the basic properties of charge — quantisation, conservation and additivity — and how conductors differ from insulators, apply Coulomb's law in vector form, add forces by superposition, and calculate electric fields and read field line patterns.
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How a Positive Medical Test Can Still Mean You Are Probably Healthy
Identify a partition of the sample space and state the theorem of total probability, use it across mutually exclusive and exhaustive causes, apply Bayes' theorem to update prior probabilities, and interpret posterior probabilities in real-life problems.
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How New Information Changes the Probability of an Event
Compute the conditional probability P(E|F) from a sample space and use its properties, apply the multiplication theorem to two or more events, and test events for independence while keeping independence separate from mutual exclusiveness.
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How a Carpenter Decides How Many Chairs and Tables to Build
Learn the language of linear programming — constraints, objective function and feasible solutions — turn real problems into linear programming problems, sketch and classify feasible regions, and find optimal solutions at corner points, including when an unbounded region has none.
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Why a Flyover and the Road Beneath It Never Meet
Find the angle between two lines in vector or Cartesian form and the conditions for perpendicular and parallel lines, recognise skew lines, compute the shortest distance between skew lines, and find the distance between parallel lines.
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How to Describe the Path of a Drone Flying in a Straight Line
Define direction cosines and direction ratios and prove l^2 + m^2 + n^2 = 1, find them for the line through two points, and write vector and Cartesian equations of a line through a point parallel to a vector or through two points.
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How Two Kinds of Vector Multiplication Measure Angles and Areas
Compute the dot product and read its geometry, use it for angles, perpendicularity and projections, compute the cross product and see why it is not commutative, and apply it to areas of triangles and parallelograms and to test parallel vectors.
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Why a Cricket Throw Needs Both a Speed and a Direction
Tell scalars from vectors and find magnitude, direction cosines and direction ratios, recognise equal, unit, zero, collinear and negative vectors and write position vectors, add vectors by the triangle and parallelogram laws, and apply the section formula.
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How an Integrating Factor Turns a Hard Equation Into an Easy One
Recognise homogeneous first order equations and solve them with y = vx, solve linear equations dy/dx + Py = Q using an integrating factor, handle the dx/dy + P1x = Q1 form, and find particular solutions from given conditions.
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How a Cooling Cup of Chai Obeys a Differential Equation
Find the order and degree of a differential equation and see when the degree is not defined, tell general solutions from particular ones and verify solutions, and solve first order equations by separating the variables and using initial conditions.
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How Calculus Finds the Area of an Ellipse-Shaped Garden
Set up definite integrals for the area between a curve and an axis, find areas enclosed by lines, circles, parabolas and ellipses in standard form, and handle regions that dip below the axis or must be split into parts.
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How Adding Up Tiny Strips Gives an Exact Area
Define the definite integral with its limits and state the Fundamental Theorem of Calculus, evaluate definite integrals with antiderivatives, change limits correctly when substituting, and use additive, reversal, even-odd and complementary-limit properties to simplify.
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Why Some Integrals Must Be Broken Into Pieces First
Use the special integrals of forms like 1/(x^2 + a^2) and their square-root versions, split rational functions into partial fractions, apply integration by parts including the e^x[f(x) + f'(x)] pattern, and integrate square roots of quadratic expressions.
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How Integration Runs Differentiation Backwards
See integration as the reverse of differentiation and why every indefinite integral carries a constant, apply standard formulae and properties, evaluate integrals by substitution, and simplify trigonometric integrands with identities before integrating.
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How to Fold a Square Sheet Into the Biggest Possible Open Box
Tell local maxima and minima from absolute extreme values and find critical points, classify them with the first and second derivative tests, and solve optimisation problems, including absolute extrema on a closed interval.
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How Fast Does a Ripple Spread When a Stone Hits a Pond?
Read a derivative as a rate of change and solve related rates problems, use the sign of the first derivative to find where a function strictly increases or decreases, and apply that behaviour to changing areas, volumes and costs.
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How to Differentiate x to the Power x Without Getting Stuck
Understand exponential and logarithmic functions and differentiate e^x and log x, use logarithmic differentiation for powers like x^x and long products, find dy/dx for curves in parametric form, and compute second order derivatives to verify relations.
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Why Some Graphs Can Be Drawn Without Lifting Your Pencil
Test continuity at a point using left-hand and right-hand limits and locate discontinuities, apply the algebra of continuous functions, use the chain rule and see why differentiability implies continuity, and differentiate inverse trigonometric and implicit functions.
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How a Matrix Inverse Solves a Whole System of Equations at Once
Build the adjoint of a square matrix and verify A(adj A) = |A|I, tell singular from non-singular matrices and compute inverses, decide whether a linear system is consistent, and solve systems with a unique solution by the matrix method.
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How One Determinant Tells You Whether Three Points Lie on a Line
Evaluate 2 by 2 and 3 by 3 determinants by expanding along any row or column, find minors and cofactors and use them to expand, and apply determinants to the area of a triangle and to test whether three points are collinear.
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Why A Times B Is Not Always B Times A for Matrices
Multiply conformable matrices and use their associative and distributive laws, see why AB and BA differ and how two non-zero matrices can multiply to zero, apply transpose rules, and split any square matrix into symmetric and skew symmetric parts.
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