Physics Section 3

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• Work done on the body equals the change in both its K.E and P.E.
• Tides raise the water level in the sea twice a day.
• The highest escape velocity in the solar system is on Jupiter.
• Gravitational P.E of a body doesn’t have a general formula.
• Doubling the speed of a moving body doubles its momentum.
• One megawatt-hour is equal to 36 x 10^8 joules.
• Work has the same dimension as torque.
• The relation between escape velocity and orbital speed is Vesc = -2Vo.
• When two protons are brought together, the potential energy between them increases.
• A child does more work than a man in lifting a weight vertically.
• The area under a force-displacement graph represents work done.
• Propulsion force of a rocket is a non-conservative force.
• Geothermal energy is a renewable source of energy.
• Photovoltaic cells convert solar energy into electrical energy.
• Biomass can be converted into fuels through direct combustion and fermentation.
• Steel possesses the highest elasticity among the given substances.
• The dimensions of stress are ML^-1T^-2.
• Strain doesn’t have the dimensions of force per unit area.
• The energy stored in a wire stretched by a force F is (FE).
• The energy stored per unit volume of a wire stretched by a force in the direction of a magnetic field is Y∝^2.
• A wire stretched by a 20N weight gains 0.01J of energy.
• The energy gained per unit volume of material when a certain stress is applied is Stress/strain.
• Stress is directly proportional to extension in the material.
• The energy stored in a wire is proportional to the square of its extension.
• Formation of large molecules from small ones is polymerization.
• The energy band occupied by valence electrons is the valence band.
• A ferromagnet fully magnetizes at its peak value of alternating current.
• Materials with tightly bound valence electrons at low temperatures are insulators.
• The angular position of crystals remains the same, called external symmetry of form.
• Homogeneity in a crystal means density of atoms remains the same along any direction.
• The band theory of solids explains the nature of all electrical conductors and insulators.
• A completely filled band is a core band.
• Nonmetals have the greatest energy gap.
• The electrical conductivity of intrinsic semiconductors increases with temperature.
• Semiconductors have a completely filled valence band, a partially filled conduction band, and a narrow forbidden band.
• Very weak magnetic fields are detected by SQUIDs.
• The energy needed to magnetize and demagnetize is represented by hysteresis loop area.
• The SI unit of modulus of elasticity is Nm^-2.
• A wire’s energy stored is 0.75J after stretching 1mm with a force of 10N.
• The energy stored in a wire stretched by a force of 10N is 0.75J.
• Ductile materials undergo plastic deformation before breaking.
• Energy stored in a wire is proportional to force and extension.
• Alteration in shape, length, or volume due to external force is deformation.
• The Curie temperature is when a ferromagnet becomes paramagnetic.
• Coercive force opposes demagnetization.
• Bulk properties relate to the microstructure of materials.
• Cleavage is the breaking of crystals along definite directions.
• In a simple cube, one atom or molecule lies at each of its eight corners.
• A vacant or partially filled band is the conduction band.
• Electrons in the conduction band are free to transport charge.
• Many semiconductors are crystals of the face-centered cubic type.
• Holes can exist in semiconductors.
• In semiconductors, charge carriers are electrons and holes.
• The net charge on n-type material is neutral.
• Magnetic force acting on a unit positive charge moving perpendicular to the magnetic field is magnetic induction.
• The current in a wire producing a force of 5N in a uniform magnetic field of 0.5 Wb/m^2 is 100A.
• Two parallel wires carrying currents in opposite directions repel each other.
• A magnetic field exerts force on a charged particle when it’s moving perpendicular to the field lines.
• Soft iron is the most suitable material for making the core of an electromagnet.
• The relationship between Tesla and Gauss is 1T = 10^4 G.
• The SI unit of flux density is NA^-1m^-1.
• The standard vector symbol for flux density is B.
• The path of an electron entering a uniform magnetic field perpendicular to it is a helix.
• The magnetic field inside a long solenoid is uniform.
• An ampere is the current that produces a force of 2 x 10^-7 N between two parallel conductors.
• The force between two parallel conductors carrying current in the same direction is attractive.
• Magnetic field lines around a conductor carrying current are concentric circles.
• The direction of the magnetic field around a straight current-carrying wire is given by the right-hand grip rule.
• The force on a conductor carrying a current in a magnetic field is perpendicular to both the current direction and the field.
• The emf induced in a conductor moving in a magnetic field is proportional to its length.
• The direction of the induced current in a loop rotating in a magnetic field reverses every half rotation.
• An increase in the number of turns in a coil increases the induced emf.
• Lenz’s law states that the direction of an induced current opposes the change causing it.
• The frequency of an AC generator is determined by the speed of rotation.
• A transformer changes high voltage and low current to low voltage and high current.
• The primary coil in a transformer is connected to the input circuit.
• A step-up transformer increases voltage and decreases current.
• The secondary coil in a transformer is connected to the output circuit.
• An inductor stores energy in its magnetic field.
• Transformers only work with AC because of changing magnetic fields.
• A step-down transformer decreases voltage and increases current.
• The primary and secondary coils of a transformer are linked by mutual induction.
• The wattage of a lamp is a measure of its power consumption.
• Electric power is the rate of energy consumption or production.
• The resistance of an ideal ammeter is zero.
• A galvanometer can be converted into an ammeter by connecting a low resistance in parallel.
• Electromotive force (emf) is measured in volts.
• An ideal voltmeter has infinite resistance.
• Ohm’s Law states that current is directly proportional to voltage and inversely proportional to resistance.
• The unit of electric energy is the kilowatt-hour (kWh).
• The direction of conventional current flow is from positive to negative.
• Electric field lines exit a positive charge and enter a negative charge.
• Electric field lines are always directed away from positive charges.
• The unit of electric flux is Nm²/C.
• Gauss’s law is based on the principle of conservation of electric charge.
• Electric field lines are closer together where the field is stronger.
• The electric field inside a conductor is zero in electrostatic equilibrium.
• The SI unit of electric potential is the volt.
• The work done to move a charge between two points is given by the product of the charge and the potential difference.
• Electric potential is a scalar quantity.