## Physics Section 3

- 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.