Definitions 2

Question 1

Brittle materials

Answer 1

Materials which do not undergo plastic deformation. Force is proportional to extension until it breaks

Question 2

Ductile materials

Answer 2

Materials which undergo plastic deformation after a considerable elastic deformation. Initially force is proportional to extension then a large extension for a small change in force

Question 3

Elastic deformation

Answer 3

Object returns to its original length (zero extension) when load is removed

Question 4

Force-extension graph

Answer 4

The area under such a graph is the work done in stretching the material; for the straight-line portion of the graph, it is a measure of the elastic potential energy stored by the material

Question 5

Hooke’s law

Answer 5

Force/load is proportional to extension/compression if proportionality limit is not exceeded

Question 6

Plastic deformation

Answer 6

Body does not return to its original shape/length when load is removed

Question 7

Strain

Answer 7

Extension over original length (ratio); stress is the cause and strain is the effect

Question 8

Stress

Answer 8

It is the force per uint cross-sectional area required to stretch a material

Question 9

Ultimate tensile strength

Answer 9

The maximum value of stress that an object can sustain before it breaks

Question 10

Ultimate tensile stress

Answer 10

The maximum value of stress that an object can sustain before it breaks

Question 11

Young’s modulus

Answer 11

Ratio of stress to strain

Question 12

Electric current

Answer 12

It is the amount of charge flowing pass a point per unit time or rate of flow of charged particles

Question 13

Ohm’s law

Answer 13

The current through a metallic conductor is proportional to the P.D across it provided that its temperature remains constant

Question 14

Potential difference

Answer 14

The energy converted from electrical to other forms of energy per unit charge that passes through it

Question 15

Quantised

Answer 15

Charge only exists in discrete amounts of 1.6x10-19 C; charge on carriers is quantised

Question 16

Resistance

Answer 16

The ratio of P.D over the current for an electrical component

Question 17

Resistivity

Answer 17

The resistivity of a wire of a particular material is its resistance for unit length

Question 18

Thermistor

Answer 18

A specific type of resistor, in which, as temperature increases, the magnitude of its resistance decreases and vice versa

Question 19

E.M.F

Answer 19

The amount of energy converted into electrical energy per unit charge supplied

Question 20

P.D

Answer 20

The amount of electrical energy converted into other forms of energy per unit charge supplied

Question 21

Internal resistance

Answer 21

The resistance inherent in a source/cell itself causing some energy to be transferred into other forms to reduce the available voltage for the rest of the circuit

Question 22

Kirchhoff’s 1st law

Answer 22

The sum of currents into a junction = sum of currents out of junction; from the conservation of charge

Question 23

Kirchhoff’s 2nd law

Answer 23

The sum of EMFs = sum of IDs around a closed loop/circuit; from the law of conservation of energy

Question 24

Potentiometer

Answer 24

A variable resistor connected as a potential divider to give a continuously variable output voltage

Question 25

Potential divider

Answer 25

Series circuits which produce an output voltage as a fraction of its input voltage; the ratio of the output voltage to the input voltage = the ratio of the output resistance over the total resistance

Question 26

Galvanometer

Answer 26

A component used to detect small changes in electric current; it is a sensitive ammeter; when the needle is not deflected, the current equals zero and the EMFs of the two sources is equal