Electricity (C8, C9, C10)

Question 1

What is charge?

Answer 1

A quantity of particles that make up matter

Question 2

What is current?

Answer 2

the rate of flow of charge

Question 3

What is a potential difference

Answer 3

the work done per unit of charge

Question 4

Why can charge be described as quantised?

Answer 4

As it takes discrete values due to the number of electrons it has or has lost (always multiples of e)

Question 5

Which end of the cell is the negative end?

Answer 5

the small fat end

Question 6

How to charges move around a circuit?

Answer 6

They are repelled from the negative end and attracted to the positive end

Question 7

What does the current depend on

Answer 7

ions in the metal (resistivity) - how easy it is fro them to move
number of electrons
size and shape of wire

Question 8

Which way does conventional current flow?

Answer 8

positive to negative

Question 9

What is an electrolyte

Answer 9

substance that carries ions (so they can act as cahrge carriers)

Question 10

Series I and V

Answer 10

Same current

share p.d.

Question 11

Parallel i and V

Answer 11

Share current

same P.d

Question 12

What is Kirchoff’s first law?

Answer 12

sum of I in = sum of I out

The algebraic sum of the curretns at a junction is zero

Question 13

Electric charge cannot be…

Answer 13

created or destroyed

Question 14

What is the number density of a material?

Answer 14

number of electrons (free) per cubic metre of a materal

Question 15

What is the mean drift velocity

Answer 15

average speed of charge carries moving in a current

Question 16

What is a I-V characterisitic?

Answer 16

Plot of current against voltage for a materia;

Question 17

What is special about a straight line IV characteristic?

Answer 17

Ohmic conductor constant resistance

- most things heat up and curve as a result

Question 18

What is special about a thermistor?

Answer 18

Most objects Temp is proportional to resitance but for a thermisytor it is inversely proportional

Question 19

Why dodes temp increase resistance in normal things?

Answer 19

ions in conductor shake nore and cause more collisions

Question 20

Why does resistance decrease when a thermistor is heated?

Answer 20

More elctrons are freed up

Question 21

Why are most things not ohmic conductors?

Answer 21

As they heat up , which gives them variable resitance

Question 22

What is resisitivity?

Answer 22

a material propety defined by its equation

Question 23

What is resisitivity measured in?

Answer 23

ohm metres

Question 24

Difference between EMF and PD

Answer 24

emf uses chemical energy to do work on electrons, pd does work on compents by turning electrical energy into other forms

Question 25

What is internal resistance

Answer 25

the resistance that is the result of having an EMF

Question 26

Difference in resistance between voltmeter and ammeter?

Answer 26

Voltmeter has very high resistance (so the current does go that way and an ammeter has a very low resitacne so not to interfere