Physics important points,tricks and hints from pmc, Etea/mdcat and pmdc past papers



*Electron Volt  is unite of electric energy.

*783Kev is the minimum electron energy in neutron beta decay.

*Proton and neutron are composed smaller particle called quark.

*Co_herent source of light means single wave length.

*Woolen cloths keep body warm bcz of bad conductivity.

*The open circuit test in a transformer is used to measure core loss.

*When bulb is turned on ohm's law is not applicable.

*If centripetal force is zero then centrifugal also zero.

*Negative of potential gradient is equal to electric intensity.

*if mass number increase density does not change.

*Acceleration in Simple pendulum is always negative to displacement.

*The Angular momentum of photon is zero.

*X_Rays used in crystallography to perform diffraction.

*Bone image is shown on X-rays photography bcz X-rays can be absorbed by bones.

*Mutual induction has a practical role in performance of transformer.

*When force is parallel to the direction of motion of the body,the work done is minimum.

*1st law of thermodynamics is special case of conservation of energy.

*In stationary wave the distance b/w adjacent node is equal to λ/2.

*An angular velocity of 60rpm is same as 2Ï€ rad/s.

*A star moving away from earth shows red shift.

*F=e(V×B)is valid for proton.

*photon cell is similar to photo electric effect.

*Alternating current generator use slip rings.

*The speed of sound in a metal is approximately 5000m/s.

*Platinum wire becomes yellow at 130 temperature.

*Plank's constant is analogous to angular momentum.

*A nucleus emits an alpha particle,followed by two beta particle the final nucleus will be an isotope of the original one.

*One redian means arc length of unit radius is unity.

*Red light photon has least momentum.

*For step down transformer Ns greater than Np.

*Basically potentiometer is a device for comparing two voltages.

*The existence of positron was discovered in cosmic radiation.

*Vs/A is unit of mutual inductance.

*B.dI=uI is expression of Ampere's law.

*IR radiation are used in green house effect.

*The role of Inductance is equal to inertia.

*volts/ampere =Ohm.

*For ideal step up transformer Ps=Pp.

*Fission and fusion both are example of renewable sources of energy.

*Perfect black body shows continuous spectrum.

*Half wave rectifier posses upper half cycle.

*the sum of absorption and transmission of light in a medium is equal to Incident light.

*Polarization explains that light is electric as well as magnetic in nature.

*Coulmb/volts=Farrad.

*The coupling co-efficient of perfectly coupled coil is one(1).

*Magnetic field density out side the solenoid is negligible.

*when object moving in a circle,the angle b/w linear velocity and position vector is 90°C.

*During Self Inductance number of turns varies as N^2.

*Energy of photon is directly proportional to frequency.

*Work done in a Isobaric process is given by Pdv.

*Angular velocity can not be infinite.

*Constant potential difference is required for establishing steady current.

*An arc of length equal to circumference of a circle subtends an angle of 2Ï€ radian.

*The angular displacement of an object after one complete revolution is "2Ï€" redian.

*Radiations are classified by its ionizing and non-ionizing nature.

*In full wave rectifier ripple factor is less.

*electric field lines due to a positive charge are radially away from the charge.

*Alpha rays used in smoke detectors.

*Wave nature of light is provided by polarization.

*Displacement of sun with respect to earth is "r".

*Instantaneous velocity is positive and negative.

*Work done by transition force in Simple pendulum is zero.

*Heavy metal used to detect radioactivity.

*Minimum energy required for pair production is 1.02Mev.

*Beats can be used to find frequency.

*The interference of green photon to red photon will cause no effect.

*Maximum power delivered by battery is Pmax=E^2/4r.

*Centrifuge is used to purify uranium.

*Momentum of photon is hf/c.

*Non-inverting amplifier circuits have very high input independence.

*Mass and energy are related to each other by Einstein law.

*The nuclear force is considered as strong force.

*Stationary Charge is not affected by magnetic field.

*Emf is equal to terminal potential difference when circuit is open.

*If we are standing in bus and driver applies a break then pseudo force pushes forward.

*According to Einstein mass energy are directly proportional.

*X-Rays is reverse process of photo electric effect.

*Momentum principle used in solar cells.

*Michelson measured the length of standard meter in terms of wave length of red candium light.

*Diode is non-ohmic resistor.

*Ripple factor of half wave rectifier is 1.21.

*Steady current does not change with time.

*Galvano meter is electro mechanical device.

*The principle behind the working of cathod rays osicilloscop is half wave rectifier.

*The value of angular momentum is maximum when angle is 90°.

*If pipe is closed at one end and open at other the closed end known as node.

*Work done on a ceiling fan by gravity is zero.

*The penetration power of x-rays depend upon frequency.

*The concept of work function was given by Einstein.

*Michelson determined velocity of light by using an octagonal rotating mirror.

*Centre tape rectifier circuit consist of 200%diode.

*Varticle velocity vs time graph for a projectile motion varies linearly.

*one of the major reasons for heat loss in transformer is Eddy current loss.

*Pseudo current may be defined as accelerating frame of reference.

*The Speed of photon in vacuum is smaller then in liquid water.

*The root mean square value of alternating current is equal to(1 under root 4)times of the peak value.

*Gamma rays can not be produce by electronic transition.

*Beta particle is actually  a fast moving electron.

*if Alpha,Beta and Gamma rays carry same momentum all have same wave length.

*Wave transport energy without transporting mattet.

*The angle b/w radius vector and centripetal acceleration is "Ï€".

*There are zero quark in electron.

*if we make the magnetic field stronger the value of induce current is increase.

*Nuclear force is spin dependent but charge independent.

*The number of diode in bridge rectifier is four(4).

*For coil self_inductance is L and current is I then flux passing through it is LI.

*Charge and momentum both are conserved in pair production.

*Ripple factor is defined as Irms/Idc.

*power transformers have maximum efficiency  at full load.

*Photon when scattered  from mirror its momentum becomes double.

*R is the thermodynamic coordinate.

*Gamma rays shows comparable penetrating power to X-rays.

*Work done by friction can be positive or negative.

*Radiation exchange occurs in vacuum.

*An ideal reversible heat engine has highest efficiency.

*The voltage turns ratio in step_down transformer is 2:1.

*The insulation b/w sheets of transformer core is to get small Eddy current.

*Acceleration of earth around sun in its orbit is always tangential.

*Emf produced in generator is NwABcos(wt).

*If direction of field and area vector is opposite then field is negative.

*The value of Rydberg constant varies with atomic number as Z^2.

*Compton confirm existence of photon.

*Acceleration can be seen in rotating frame of reference.

*In Ultra violet region photon has highest energy.

*The resistance of super conductor is zero.

*Half-life is measured by Geiger Muller counter.

*Co_Herent sources are monochromatic sources which produce waves of constant phase difference.

*The fission reaction is slow reaction when neutrons slow down.

*According to wien's law temperature and wave length are inversely related.

*Value of current in short circuit is infinite.

*Spectral lines is like a finger print of absorbed or emission energy in a spectrum.

*In half wave rectification the diode conducts during positive half.

*The reverse process of pair production is known as annihilation of energy.

*Heavy water used to reduce the speed of fast moving neutron.

*The net force in an inertial frame is zero.

*The speed of sound in water is approximately 1500m/s.

*The resistance of human body is about 120k-ohm.

*Quarks are half spin particle.

*whene sound reflects back its known as echo sound.

*wave nature and particle nature of photon related to its momentum.

*In SONAR we use sound waves.

*Power remain unchanged in transformer.

*Projectile motion does not depend upon mass.

*The Alternating current can be converted into direct current by Rectification.

*Phosphorus-32 and strontium-90 used for skin cancer.

*Copper has low electrical resistivity.

*S.I unit of radioactivity  is Becqueral.

*The speed of waves depend upon tension and mass per unit length of string.

*Very hot star emit blue colour.

*Projectile motion of object on earth always parabolic.

*Life time of an excited state is 10^-8s.

*1Rutherford is equal to 10^6becqueral.

*Atmosphere around the earth help by gravity.

*Momentum of white light is less than X-rays.

*Acceleration always positive for free falling body.

*H-atom can not produce Alpha rays.

*The black body which is close to perfect body is cavity radiator.

*S.I unit of Inductance is Henry.

*In stationary wave strain is maximum at node.

*Photocopier and ink-jet printer are applications of electrostatics.

*Temperature is defined by zeroth law of thermodynamics.

*The speed of sound in air is approximately 332m/s.

*Microscope uses shorter wavelength to reduce diffraction.

*The core of earth is hot due to frictional force.

*Centre tap rectifier circuit consist of 200%diode.

*Newtons 1st law falsified Aristotle theory.

*Angular frequency directly related to linear frequency.

*Breather is provided to transformer to absorb moisture of air during breathing.

*if number of loops increase than according to Faraday's law magnetic field,electric field and voltage also increase.

*The greek word"xeros and graphos means dry writing.

*Laser light is uni-directional.

*X-Rays were discovered in scattering experiment.

*Lenz law is in accordance with conservation of energy.

*Resistance of conductor depends upon length.

*A cycle tyres burst suddenly is an example of Adiabatic process.

*Molar mass of water is 0.108kg/mol.

*In A.C generator increase in number of turns in the coil increase emf.

*The electric potential at infinite distance  zero.

*In fusion reaction of sun H isotopes are used.

*Alpha rays has highest charge.

*Young's double slit experiment support Huygen's wave theory.

*In Lorentz force magnetic force is deflecting force.

*The effect of nuclear bomb radiation lasts for more than 90years.

*In Compton scattering process wave length of scattered X-rays Increase.

*In stationary wave the distance between two consecutive crests is 1/2wavelength.

*In full wave rectifier with input frequency of 50Hz the ripple in output is mainly of the frequency of 100Hz.

*Pair production is possible in gamma rays photon.

*Electric field generate due to induction is conservative.

*S.I unit of equivalent dose is Sievert.

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