definitions 3

Question 1

Einstein’s first postulate?

Answer 1

Physical behaviour cannot depend on any “absolute velocity”. Physical laws must take the same form for all observers, no matter what their state of uniform motion in a straight line.

Question 2

Einstein’s second postulate?

Answer 2

The speed of light, c, is a universal constant. It has the same value, regardless of the motion of the platform from which it is observed. The translation between distance and time units is the same for everybody.

Question 3

Elastic deformation?

Answer 3

When a material regains its original shape after deformation.

Question 4

Elastic limit?

Answer 4

The maximum stress at which an object returns to its original shape after the deforming stress is removed.

Question 5

Electric field?

Answer 5

The region surrounding an electrical charge in which another electrical charge would experience a force.

Question 6

Electric field strength?

Answer 6

The magnitude and direction of the force on a charge of 1 coulomb at a given point in an electric field. Symbol, E. Units N/C or V/M

Question 7

Electric force constant, k?

Answer 7

The constant of proportionality, k, in coulombs law.

Question 8

Electric potential?

Answer 8

The electrical energy per coulomb of a charge at a specific point, being the work done to move 1C from infinity to the place in question. Measured in V or J/C

Question 9

Electrical conductivity, σ?

Answer 9

A constant for electrical conductors given by the equation:
G =σA/L

Question 10

Electrical permittivity of free space?

Answer 10

A fundamental property of free space, ε0, related to the electric force constant, k, given by:
k=1/(4πε)

Question 11

Electrical resistivity, ρ ?

Answer 11

E constant for electrical conductors given by the equation:

R= (ρL)/A

Question 12

Electron?

Answer 12

A fundamental particle, a lepton of -1.6*10^-19 C

Question 13

Electronvolt(eV)?

Answer 13

A practical measure of energy used in atomic and nuclear physics, given by the energy gained by an electron falling through a p.d. of 1V, where one eV is 1.6*10^-19 J.

Question 14

Energy?

Answer 14

A measure of the capacity of a body or system for doing work.

Question 15

Energy level?

Answer 15

Confined quantum objects, such as electrons in an atom, exist in discrete quantum states each with a definite energy. This term refers to the energy of one or more such quantum states. (Different states can have the same energy)

Question 16

Energy transferred thermally?

Answer 16

Energy transfer associated with temperature change. E.g. frictional work can raise the temp of a moving object.

Question 17

Equilibrium position?

Answer 17

The position of an oscillator in which no net force is acting.

Question 18

Equipotential surface?

Answer 18

A continual surface joining points of the same potential in a 3D field. E.g grav or electric

Question 19

Exponential?

Answer 19

A process in which the rate of change of a quantity is proportional to the value of the quantity.

Question 20

Faraday’s law of electromagnetic induction?

Answer 20

The induced emf,ε , is proportional to negative rate of change of flux.
ε= -d(NΦ)/dt

Question 21

First law of thermodynamics?

Answer 21

The change in internal energy, delta U is equal to the sum of the work done on a system and the energy transferred thermally into it.
ΔU = W + Q

Question 22

Flux linkage?

Answer 22

Number of coils * Flux through one coil. Measured in Weber (Wb).

Question 23

Focal length?

Answer 23

The distance from the centre of a thin lense to the focal point.

Question 24

Focal point (focus)?

Answer 24

The point where light from a very long distance along the axis of a converging lens is brought to a focus by the lens. This point is also called the focus.

Question 25

Force constant?

Answer 25

The ratio of force/extension for an elastic specimen.

Question 26

Forced oscillation?

Answer 26

An oscillation driven by the action of a periodic driving force.

Question 27

Fracture?

Answer 27

When an object breaks into two or more pieces when placed under pressure.

Question 28

Fracture stress?

Answer 28

The stress at which fracture occurs. Fracture stress of a material under tension is often called it’s tensile strength.

Question 29

Free oscillator?

Answer 29

An oscillation due to a restoring force, without any damping or driving forces.

Question 30

Frequency?

Answer 30

For simple harmonic oscillators, the number of complete oscillations in unit time.