Definitions-SOME MISSING Flashcards
DEFINE : Potential difference
between two points
The work done per unit charge in moving a charge between two points
Current
The rate of flow of charge
EMF
The energy supplied per unit charge by a cell to charge passing through it. It
is equal to the terminal p.d. when no current flows
Or
the energy provided by a cell or battery per coulomb of charge passing through it, it is measured in volts (V)
Resistance
The ratio of the potential difference across a component to the current
through it. (Not the gradient of a V-I plot)
Resisitivity
The product of a material’s resistance and cross-sectional area per unit
length. (Numerically equal to the resistance between opposite faces of a 1m3
piece of the material).
Density
The mass per unit volume of a material
Hooke’s Law
For a material that obeys Hooke’s law the extension of the material will be in
direct proportion to the load applied up to the limit of proportionality.
Young’s modulus
The ratio of tensile stress to tensile strain for a material in the linear region
of its stress/strain graph.
Refractive index
The ratio of the speed of light in a vacuum to the speed of light in the material
(always > 1)
Newton’s 1st law
A body will continue at constant velocity unless acted on by a resultant force.
Newton’s 2nd law
Resultant force equals rate of change of momentum and acts in the same
direction as the momentum change.
(Special case when mass is constant: Force equals mass x acceleration).
Newton’s 3rd law
In any interaction the two bodies exert equal and opposite forces on each
other.
Conditions for
equilibrium
The resultant force in any direction on a body is zero, and the resultant
moment about any point is zero.
Mechanical work
The product of the force and the direction moved in the direction of the
force. (Force and displacement)
Power
The rate of doing work
Moment or torque of a force
The force multiplied by the perpendicular distance between the pivot and
the line of action of the force.
Velocity
Rate of change of displacement
Acceleration
Rate of change of velocity
Momentum
The product of a body’s mass and velocity. It is a vector that acts in the
same direction as the velocity.
Motion in a circular
path at constant speed
Implies there is an acceleration and requires a centripetal force.
Condition for SHM
The acceleration is proportional to the displacement and in the opposite
direction.
Damping
Reduces the amplitude at resonance (resonance curve becomes less sharp)
and the resonant frequency decreases slightly as damping is increased.
Newton’s Universal
Law of Gravitation
The force between two masses is proportional to the product of the masses
and inversely proportional to the square of the distance between their
centres.
Gravitational field
strength
The force per unit mass on a small test mass at that point.
Gravitational potential
The work done per unit mass in moving a small test mass from infinity to
that point. The value of gravitational potential at infinity is zero.
Coulomb’s Law
The force between two charged objects is proportional to the product of their
charges and inversely proportional to the square of the distance between
their centres.
Electric field strength
The force per unit charge on a small positive test charge at that point.
Electric potential
The work done per unit charge in moving a small positive test charge from
infinity to that point. The value of electrical potential at infinity is zero.
Time constant
The time it takes for the charge/voltage/current in an RC circuit to fall to 1/e of its starting value.
Faraday’s law
The induced emf is equal to the rate of change of flux linkage.
Lenz’s law
The direction of the induced emf is such that it will oppose the change of flux
causing it.
Internal energy
Is the sum of the randomly distributed kinetic energies and potential energies
of the particles in a body. For an ideal gas internal energy is the kinetic
energy of the atoms.
Specific latent heat of
fusion
The energy required per unit mass to turn a material from the solid state to
the liquid state without change of temperature.
Specific latent heat of
vaporisation
The energy required per unit mass to turn a material from the liquid state to
a gas without change of temperature.
Specific heat capacity
The energy required per unit mass to raise the temperature of a material by
1K.
