Chapter 8 - Charge And Current

Question 1

Electric current

Answer 1

The rate of flow of charge, symbol I, measures in amperes A: a normal flow of electrons or flow of ions in electrolytes

Question 2

Electric charge

Answer 2

A physical property, symbol q or Q, either positive or negative, measured in coulombs C or as a relative charge

Question 3

Positive charge

Answer 3

A type of electric charge - positively charged objects attract negatively charged ones and repeal other positive charges

Question 4

Negative charge

Answer 4

A type of electric charge, negatively charged objects attract positively charged ones and repel other negative ones

Question 5

Coulombs

Answer 5

The derived SI unit of electrical charge, symbol C - 1 coulomb of electric charge passes a point in one second when there is an electric current of one ampere 1C=1A

Question 6

Ions

Answer 6

An atom that has either lost or gained electrons and so has a net charge

Question 7

Relative charge

Answer 7

A simplified measurement of the electric charge of a particle or object, measured as multiples of elementary charge

Question 8

Elementary charge

Answer 8

The electric charge equivalent to the charge on a proton, 1.60x10^-19C symbol e

Question 9

Quantisation

Answer 9

The availability of some quantities, such as energy or charge, only in certain discrete values

Question 10

free electrons/delocalised electron

Answer 10

An electron in a metal that is not bound to an atom and is free to move

Question 11

Conventional current

Answer 11

A model used to describe electric current in a circuit - conventional current travels from positive to negative - the direction in which positive charges would travel

Question 12

Electrolytes

Answer 12

A liquid containing ions that are free to move and so to conduct electricity

Question 13

Ionic solution

Answer 13

An ionic compound dissolved in a liquid to form an electrolyte

Question 14

Cation

Answer 14

A positively charged ion, which is attracted to a cathode

Question 15

Anion

Answer 15

A negatively charged ion, which is attracted to an anode

Question 16

Anode

Answer 16

A positively charged electrode

Question 17

Cathode

Answer 17

A negatively charged electrode

Question 18

Ammeter

Answer 18

A device used to measure electric current-it must be placed in series and ideally have zero resistance

Question 19

Resistance

Answer 19

A property of a component calculated by dividing the potential difference across it by the current in it, symbol R, unit ohm (horse shoe shape)

Question 20

Conservation of charge

Answer 20

A conservation law which states that electric charge can neither be created nor destroyed - the total charge in any interaction must be the same before and after the interaction

Question 21

Kirchoff’s first law

Answer 21

At any point in an electrical circuit, the sum of the e.m.fs is equal to the sum of the p.d’s. Current in=current out EI in = EI out

Question 22

Number density

Answer 22

The number of free electrons per cubic meter of material, symbol n, unit m^-3

Question 23

Semiconductor

Answer 23

A material with a lower number density than a typical conductor, e.g. Silicon

Question 24

Mean drift velocity

Answer 24

The average velocity of electrons as they move through a wire, symbol v unit ms^-1