Electricity and electrostatics

Question 1

what do conductors do

Answer 1

they allow charged particles to move through it. The delocalised sea of electrons in a metal wire are free to move

Question 2

what do cells/batteries do

Answer 2

more electrons will move towards the positive terminal. there is a net flow of current through the wire

Question 3

which way do electrons flow

Answer 3

they flow from positive to negative terminal(syllabus of iGCSE) but actually they flow from the negative terminal to the positive terminal because electrons are negatively charged

Question 4

definition of charge

Answer 4

Charge is a property of a body which experiences a force in an electric field

Question 5

definition of current

Answer 5

rate of flow of charge

Question 6

what is the equation linking charge, current and time

Answer 6

Q = I x T (charge (coulombs[c]) = current(amperes[A]) x time(seconds[s]))

Question 7

what does a cell do

Answer 7

gives energy to the elctrons

Question 8

what does a wire do

Answer 8

carries current

Question 9

what do bulbs do

Answer 9

converts electrical energy to light

Question 10

what do ammeters do

Answer 10

measures the current

Question 11

what do resistors do

Answer 11

opposes flow of electrons

Question 12

how does current work in series

Answer 12

current stays the same everywhere in series

Question 13

how does the current in parallel circuits work

Answer 13

the current will go into paths proportional to the resistance following the rule V = IR

Question 14

what is voltage

Answer 14

energy/charge

Question 15

how does voltage work in series circuit

Answer 15

the total voltage will be split proportionally to the resistance of the components following the rule V = IR (if the resistance increases, the voltage will also increase

Question 16

how does voltage work in parallel

Answer 16

the voltage will be the same everywhere, unless there are multiple components in a single path

Question 17

how many joules of energy is given to each coulomb of charge that passes through the cell if the cell is 1.5V?

Answer 17

1.5J of energy

Question 18

formula linking voltage, energy and charge

Answer 18

V = E(J)/Q(C)

Question 19

how can you measure voltage

Answer 19

measure voltage using a voltmeter which is connected in parallel with the component we are interested in

Question 20

rules for resistance in series

Answer 20

R1 + R2 = RT(total)

Question 21

rules for resistance in parallel

Answer 21

1/R1 + 1R2 = 1/RT

Question 22

why does resistant increase in an filament Light bulb

Answer 22

-The current increases, which leads to the the electrons transferring more KE to the metal ions
-The ions vibrate more, increasing the chance of electrons scattering, so the resistance increases

Question 23

what name is given to a light bulb that doesnt increase resistance as the current increases

Answer 23

ohmic

Question 24

what is a diode

Answer 24

a semi-conductcor device that only allow current to flow one way

Question 25

what is a thermistor

Answer 25

The resistance of a thermistor depends on its temperature. At low temperatures, the thermistor has a high resistance. As the temperature increases, the resistance decreases.

Question 26

uses of a thermistor

Answer 26

A thermistor can be used in thermostats or heat activated fire alarms.

Question 27

what is an LDR

Answer 27

The resistance of a LDR depends on light intensity. At low light levels, the LDR has a high resistance. As the light intensity increases, the resistance decreases.

Question 28

uses of an LDR

Answer 28

A LDR can be used as a sensor in cameras or automatic lights that come on when it gets dark.

Question 29

what are diodes used for

Answer 29

converting alternating current into direct current

Question 30

why does the resistance increase of a filament lamp as the voltage increases?

Answer 30

-lamp heats up due to higher voltage
-ions vibrate more
-greater chance of electron collisions
-resistance increases

Question 31

memorise symbols

Answer 31

-google it

Question 32

why should domestic lighting be in a parallel circuit

Answer 32

-allows lights to work independently
-they all get the same mains voltage (230V)
-so different areas can get different light intensities

Question 33

electrical conductors

Answer 33

conducts charge easily

Question 34

electrical insulators

Answer 34

do not conduct charge very well so current cannot flow

Question 35

what is a static charge

Answer 35

charge which builds up in one space and is not free to move

Question 36

what causes sparks

Answer 36

-when an electrical charge builds up on an isolated object, the voltage between the object and the earth increases
-if the voltage gets large enough, electrons can jump across the gap between the charged object and earth/earthed object, causing a spark

Question 37

how is static electricity helpful in an inkjet printer

Answer 37

-droplets of ink are forced out of a fine nozzle, and are then given an electrical charge
-droplets are deflected as they pass between two metal plates. A voltage is given to the plates, one is -ve, one is +ve
-droplets are attracted to the plate of the opposite charge and are repelled from the plate with the same charge
-size and direction of the voltage across each plate changes so each droplet is deflected to hit a different place on the paper

Question 38

how is static electricity helpful for photocopiers

Answer 38

-image plate is +vely charged. An image of what you are copying is projected onto it.
-whiter bits of what you are copying make light fall on the plate and the charge leaks away there
-charged bits attract negatively charged black powder, which is then transferred onto positively charged paper
-paper is heated so the powder sticks