Definitions-SOME MISSING

Question 1

DEFINE : Potential difference

between two points

Answer 1

The work done per unit charge in moving a charge between two points

Question 2

Current

Answer 2

The rate of flow of charge

Question 3

EMF

Answer 3

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)

Question 4

Resistance

Answer 4

The ratio of the potential difference across a component to the current
through it. (Not the gradient of a V-I plot)

Question 5

Resisitivity

Answer 5

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).

Question 6

Density

Answer 6

The mass per unit volume of a material

Question 7

Hooke’s Law

Answer 7

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.

Question 8

Young’s modulus

Answer 8

The ratio of tensile stress to tensile strain for a material in the linear region
of its stress/strain graph.

Question 9

Refractive index

Answer 9

The ratio of the speed of light in a vacuum to the speed of light in the material
(always > 1)

Question 10

Newton’s 1st law

Answer 10

A body will continue at constant velocity unless acted on by a resultant force.

Question 11

Newton’s 2nd law

Answer 11

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).

Question 12

Newton’s 3rd law

Answer 12

In any interaction the two bodies exert equal and opposite forces on each
other.

Question 13

Conditions for

equilibrium

Answer 13

The resultant force in any direction on a body is zero, and the resultant
moment about any point is zero.

Question 14

Mechanical work

Answer 14

The product of the force and the direction moved in the direction of the
force. (Force and displacement)

Question 15

Power

Answer 15

The rate of doing work

Question 16

Moment or torque of a force

Answer 16

The force multiplied by the perpendicular distance between the pivot and
the line of action of the force.

Question 17

Velocity

Answer 17

Rate of change of displacement

Question 18

Acceleration

Answer 18

Rate of change of velocity

Question 19

Momentum

Answer 19

The product of a body’s mass and velocity. It is a vector that acts in the
same direction as the velocity.

Question 20

Motion in a circular

path at constant speed

Answer 20

Implies there is an acceleration and requires a centripetal force.

Question 21

Condition for SHM

Answer 21

The acceleration is proportional to the displacement and in the opposite
direction.

Question 22

Damping

Answer 22

Reduces the amplitude at resonance (resonance curve becomes less sharp)
and the resonant frequency decreases slightly as damping is increased.

Question 23

Newton’s Universal

Law of Gravitation

Answer 23

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.

Question 24

Gravitational field

strength

Answer 24

The force per unit mass on a small test mass at that point.

Question 25

Gravitational potential

Answer 25

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.

Question 26

Coulomb’s Law

Answer 26

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.

Question 27

Electric field strength

Answer 27

The force per unit charge on a small positive test charge at that point.

Question 28

Electric potential

Answer 28

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.

Question 29

Time constant

Answer 29

The time it takes for the charge/voltage/current in an RC circuit to fall to 1/e of its starting value.

Question 30

Faraday’s law

Answer 30

The induced emf is equal to the rate of change of flux linkage.

Question 31

Lenz’s law

Answer 31

The direction of the induced emf is such that it will oppose the change of flux
causing it.

Question 32

Internal energy

Answer 32

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.

Question 33

Specific latent heat of

fusion

Answer 33

The energy required per unit mass to turn a material from the solid state to
the liquid state without change of temperature.

Question 34

Specific latent heat of

vaporisation

Answer 34

The energy required per unit mass to turn a material from the liquid state to
a gas without change of temperature.

Question 35

Specific heat capacity

Answer 35

The energy required per unit mass to raise the temperature of a material by
1K.