Electricity 2

Question 1

what makes metals such good conductors

Answer 1

they have lots of free electrons that can flow easily

Question 2

why do insulators not carry electricity

Answer 2

they dont have any free electrons

Question 3

define ressistance

Answer 3

how hard it is for the electrons to move through a component

Question 4

what is resistance measured in

Answer 4

ohms

Question 5

why do high resistance wires get hot

Answer 5

because the electrons are hitting the atoms, transferring energy to them as heat

Question 6

why does heat a component increase resistance in it

Answer 6

as atoms are vibrating faster, electrons bump into more of them, so its more difficult to get through

Question 7

power is

Answer 7

the rate energy is transferred by an appliance

Question 8

power is measure in

Answer 8

watts (W)

Question 9

power equation

Answer 9

P = E/t (power (W) = energy (J) / time (s))

Question 10

potential difference =

Answer 10

current X resistance

Question 11

AC is

Answer 11

alternating current - comes from a generator - potential difference goes above and below 0

Question 12

DC is

Answer 12

Direct current - comes from batteries and solar panels - potential difference always positive

Question 13

mains electricity

Answer 13

at 230v and 50Hz

Question 14

energy transferred =

Answer 14

power (watts) / time (secs)

Question 15

What is static electricity

Answer 15

when insulators are rubbed against each other (!) electrons rub off one onto the other - creating charge

Question 16

in static charge

Answer 16

gain of electrons create negative charge

Question 17

charge is

Answer 17

number of electrons in coulombs - 1 coulomb = 100000000000000000000 electrons!!!!

Question 18

electrons move very easily through

Answer 18

metals

Question 19

electric current =

Answer 19

charge (C) / time (s)

Question 20

current potential difference graphs show

Answer 20

a straight line for constant resistance - gradient = resistance

Question 21

voltage =

Answer 21

current X resistance

Question 22

resistors in series circuits

Answer 22

add resistance together

Question 23

current in series

Answer 23

same through whole circuit

Question 24

voltage in series

Answer 24

shared between components

Question 25

current in parallel

Answer 25

all braches add up to current in main branch

Question 26

voltage in parallel

Answer 26

voltage in each branch same as every other branch

Question 27

resistance in bulb

Answer 27

goes up as it gets hotter

Question 28

diode

Answer 28

only lets current through in one direction - if potential difference is negative no current flows

Question 29

light emitting diode (LED)

Answer 29

gives light if current flows in one direction

becoming commen for of light as give out no heat, so very efficient (cheap!!)

Question 30

light dependent resistors

Answer 30

as light increases resistance decreases

used in light sensors.

Question 31

thermistors

Answer 31

as heat increases resistance increases

used in thermostats

Question 32

variable resistors

Answer 32

dial on them changes resistance

used in dimmer switches

Question 33

fuses work because

Answer 33

when too high a current goes through they over heat and melt - breaks the current

Question 34

circuit breakers work because

Answer 34

when too high a current goes through they flick a switch, turning off current - can be turned back on

Question 35

residual current circuit breakers (RCCBs) work because

Answer 35

they sense difference between live and neutral cable - if too great they switch off - much faster than fuses or circuit breakers

Question 36

Willbling man games subscribe

Answer 36

Hi