Definitions Flashcards
Speed
Distance travelled per unit time
Velocity
Rate of change of displacement
Acceleration
Rate of change of velocity
Mass
Mass is the amount of matter in a body
Weight
Amount of gravitational force acting on a body
Gravitational Field
A region in which a mass experiences a force due to gravitational attraction
Gravitational Field Strength
gravitational force acting per unit mass placed at that point.
Inertia
Reluctance of a body to change its state of rest or motion due to its mass
Moment
product of the force and the perpendicular distance from pivot to force
Principle of Moments
For a body in an equilibrium (balanced), the total sum of clockwise moments about any point is equal to the total sum of anti-clockwise moments about the same point.
Center of Gravity
a point where all the weight of the object appears to act on, regardless of its orientation.
Pressure
force acting per unit area.
Pascal’s Principle
A pressure applied to an enclosed liquid will betransmitted equallyto all parts of the liquid.
Energy
the capacity to do work
Principle of conservation of energy
Energy cannot be created or destroyed. Energy can be transferred from one store to another. The total energy of an isolated* system is constant
Kinetic Energy
energy possessed by an object due to its motion
Gravitational Potential Energy
Energy possessed by an object due its mass and position in a gravitational field
Work
product of the force and the distance moved by the object in the direction of the force.
Power
Power is defined as rate of energy transfer
Efficiency
Efficiency is the ratio of useful energy output to the total energy input as a percentage
Conduction
transfer of thermal energy due to collisions/vibrations of particles
Convection
Transfer of thermal energy by means of convection currents of a fluid, due to a difference in density
Radiation
Transfer of thermal energy by infrared radiation without the need for a medium
Specific Heat Capacity
amount of thermal energy required to raise the temperature of a unit mass (e.g. 1 kg) of a substance by 1 K (or 1°C).
Specific Latent Heat of Fusion
Amount of thermal energy required to change a unit mass (e.g. 1 kg) of the substance from a solid state to a liquid state (or vice versa), without a change in temperature
Temperature
average kinetic energyof all the particles in the body.
Internal Energy
totalkinetic energyassociated with the motion of the particles and the totalpotential energybetweenintermolecular forces
Waves
transfer of energy through a medium with no net movement of medium
Frequency
number of complete waves produced per second
Wavelength
Shortest Distance between two consecutive throughs or crests or any two points in phase
Period
Time taken for one complete wave to be produced
Amplitude
Maximum displacement of wave from rest or equillibrium position
In phase
Any two points on a wave that have the same displacement from rest position and moving in the same direction
Wavefront
An imaginary line on the wave that connects all adjacent points that are in phase.
Transverse Wave
Wave which travel in a direction perpendicular to the vibration of particles
Longitudinal Waves
Waves which travel in a direction parallel to the vibration of particles
Ultrasound
Sound with frequencies above the upper limit of human range of audibility
Refraction
bending of light due to a change in speed of light as light rays travel from one optical medium to another medium.
Total internal reflection
Complete reflection of a light ray in an optically denser medium at the boundary with an optically less dense medium
Critical angle
Angle of incidence in the optically denser medium where the an angle of refraction in the optically less dense medium is 90°.
Focal Point
Point where a parallel beam of light will converge at after passing through the lens.
Focal Length
Distance between the centre of the lens and the focal point.
Law of electrostatics
Unlike charges attract and like charges repel
Electric field
An electric field is region in which an electric charge experiences a force.
Current
rate of flow of electric charge.
Potential Difference
thework doneto driveunit chargethrough thecomponent.
e.m.f
work doneby the source in drivingunit chargearound a complete circuit.
resistance
ratio of the potential difference across it to the current flowing through it.
Transducers
transduceris an electrical device that converts energy from one form to another
Ohms Law
Current through a metallic conductor is directly proportional to the potential difference across it, provided that physical conditions (such as temperature) remain constant
Semiconductor diode
Device that allows current to flow in one direction only
Magnetic Field
Magnetic field is a region in which the force of magnetism acts.
North Pole of a Magnet
End of the magnet that points to the Earth’s Geographical North Pole
Split-ring commutator
reverse the direction of the current in the coil every half a revolution so that the coil continues to turn in the same direction.
Faradays Law
Magnitude of the induced electromotive force in any closed circuit is directly proportional to the rate of change of the magnetic flux through the circuit.
Lenz Law
Direction of the induced e.m.f. (and hence the direction of the induced current) in a closed circuit is such that its magnetic effect always opposes the change causing it
a.c current
electric current that changes its direction of flow with time
Alternating Voltage
Positive and negative terminals of electrical source switches at regular intervals
Slip rings
provide an electrical contact between carbon brushes and the coil
Proton number
number of protons of an element
Nucleon number
Total number of neutrons and protons in the nucleus of an atom
Isotopes
Atoms of the same element that have the same number of protons but different number of neutrons
Radioactive decay
Random and spontaneous process by which an unstable atomic nucleus loses its energy by emission of electromagnetic radiation or particle(s).
Half-life
time taken for half the remaining unstable nuclei in a radioactive sample to decay.
Nuclear fission
Process in which the nucleus of an atom splits and releases a huge amount of energy.
Nuclear fusion
process in which 2 light atomic nuclei combine to form one heavier atomic nucleus and releases a huge amount of energy.
