Short interactive lessons that ask a question before they explain. One session takes about ten minutes and ends with questions to check what you have understood.
Like charges repel and unlike charges attract. Charge is additive, conserved and quantised.
Class 12 · Physics Charge and the Field Around It FreeThe force between two point charges is proportional to their product and to 1/r².
Class 12 · Physics Charge and the Field Around It FreeThe total force on a charge is the vector sum of the forces each other charge exerts alone.
Class 12 · Physics Charge and the Field Around It FreeThe field is the force per unit charge at each point. A charge q in a field E feels F = qE.
Class 12 · Physics Charge and the Field Around It FreeField lines show the field’s direction and strength; flux Φ = EA cos θ measures the field through a surface.
Class 12 · Physics Charge and the Field Around It FreeEqual and opposite charges a small distance apart. In a uniform field: no net force, but a torque pE sin θ.
Class 12 · Physics Charge and the Field Around It FreeThe flux out of any closed surface equals the enclosed charge divided by ε₀.
Class 12 · Chemistry Solutions FreeMass percentage, mole fraction, molarity and molality. Only the volume-based measures change with temperature.
Class 12 · Chemistry Solutions FreeSolubility of solids depends mainly on temperature. For gases, solubility is proportional to pressure.
Class 12 · Chemistry Solutions FreeEach component’s partial vapour pressure is its pure vapour pressure times its mole fraction.
Class 12 · Chemistry Solutions FreeWeaker or stronger attraction between unlike molecules raises or lowers the vapour pressure. Azeotropes.
Class 12 · Chemistry Solutions FreeFour properties that depend only on the number of solute particles, each usable to find a molar mass.
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