Electricity

Question 1

what is a cell / battery?

Answer 1

a source of electrical energy and voltage

Question 2

what does a switch do?

Answer 2

complete or break a circuit

Question 3

what does a bulb do?

Answer 3

produce light when a current is supplied

Question 4

how does a bulb produce light?

Answer 4

heating a filament wire

Question 5

what does a resistor do?

Answer 5

reduce current flow and provides resistance

Question 6

what is a variable resistor?

Answer 6

a resistor we can vary the resistance of

Question 7

what does a voltmeter measure?

Answer 7

the voltage / potential difference across a circuit or component

Question 8

what does an ammeter measure?

Answer 8

the current at a point in a circuit

Question 9

what is a fuse designed to do?

Answer 9

break / melt under high currents

Question 10

what does a diode act as?

Answer 10

a one-way switch for a current

Question 11

what do LEDs do?

Answer 11

convert electrical energy directly into light

Question 12

what is a LDR?

Answer 12

a resistor whose value depends on light intensity

Question 13

what is a thermistor?

Answer 13

a resistor that varies with temperature

Question 14

what is the definition of electric current?

Answer 14

the rat of flow of charge

Question 15

what is the electric current measured in?

Answer 15

Amperes (A)

Question 16

what is the electric current equation?

Answer 16

Q=Ixt

Question 17

what is the definition of voltage?

Answer 17

energy transferred per unit charge

Question 18

what is voltage measured in?

Answer 18

volts (V)

Question 19

what is the voltage equation?

Answer 19

V=E/Q

Question 20

what is the definition of resistance?

Answer 20

the opposition to the flow of current

Question 21

what is resistance measured in?

Answer 21

ohms

Question 22

what is resistance affected by?

Answer 22

temperature, cross sectional are, length and material

Question 23

how does temperature effect resistance?

Answer 23

as temp increases, resistance increases

Question 24

how does the cross sectional area effect resistance?

Answer 24

as the cross sectional area increases, resistance decreases

Question 25

how does length affect resistance?

Answer 25

as length increases, resistance increases

Question 26

what is the ohm's law equation?

Answer 26

V = I x R

Question 27

what is ohm's law?

Answer 27

for a component of fixed resistance, current is directly proportional to the voltage

Question 28

what are 3 advantages of series circuits?

Answer 28

easier to set up / wire, lower voltage bulbs are required and the battery lasts longer

Question 29

what are 3 disadvantages of series circuits?

Answer 29

if one component breaks, the whole circuit breaks; each bulb receives less voltage; hard to diagnose individually broken components

Question 30

what are 3 advantages of parallel circuits?

Answer 30

each bulb receives a greater voltage, circuit won't break when one component breaks, easy to diagnose broken components

Question 31

what are 2 disadvantages of parallel circuits?

Answer 31

more complicated to set up, battery doesn't last as long

Question 32

what is the definition of power?

Answer 32

the rate of work done / the rate at which energy is transferred

Question 33

what is the power, work done equation?

Answer 33

power = work done / time

Question 34

what is the power, energy equation?

Answer 34

power = current x voltage

Question 35

what is power measured in?

Answer 35

watts

Question 36

how does the current flow as a direct current?

Answer 36

always the same way

Question 37

how does the current flow as alternating current?

Answer 37

it constantly changes direction

Question 38

does convectional current flow positive to negative?

Answer 38

yes

Question 39

do electrons flow from positive to negative?

Answer 39

no, electrons flow form negative to positive (opposite to current)

Question 40

what is the frequency of mains electricity and what type of current is it?

Answer 40

50Hz as alternating current

Question 41

what is the DC equivalent voltage for the mains electricity?

Answer 41

230V

Question 42

what colour is the live wire and what type of current runs through it?

Answer 42

brown with alternating current

Question 43

what colour is the neutral wire and what is it set at and why?

Answer 43

blue, it is set at 0V to complete the circuit

Question 44

what colours is the earth wire and what is it?

Answer 44

green + yellow - a safety feature if the is a fault

Question 45

what are the 2 main hazards of mains electricity?

Answer 45

electrocution + fires

Question 46

how does electrocution occur and what is used to prevent this?

Answer 46

happens when contact is made with the live wire - the earth wire and a fuse / circuit breaker can help to prevent this

Question 47

how do electrical fires occur and what is used to prevent this?

Answer 47

happens when a current that is too high flows through appliances or cables - a fuse or circuit breaker can be used to limit the current to safe levels

Question 48

true or false? the thinner the fuse wire, the more current is required to cause it to melt?

Answer 48

false, the thicker the fuse wire, the more current is required to cause it to melt

Question 49

what happens if the casing of a wire / plug becomes live?

Answer 49

the earth wire provides a low resistance path to earth

Question 50

what is double insulation and what does it do?

Answer 50

it has an outer casing that is made out of plastic - a good insulator - so current cannot flow

Question 51

what is a circuit breaker?

Answer 51

an electromagnetic device that breaks when the current exceeds a certain value

Question 52

how does a circuit breaker work?

Answer 52

the electromagnet is always turned on so if there is a current (power) surge, then the electromagnet becomes stronger. the magnetic field produced is strong enough to attract the iron armature so the contacts are pulled apart which breaks the circuit

Question 53

can circuit breakers be reset?

Answer 53

yes by pressing a button

Question 54

what is an electrical conductor?

Answer 54

a material that allows electrons to flow through it

Question 55

what is an electrical insulator?

Answer 55

a material that does not allow electrons to flow through it

Question 56

what is static charge and where is it most commonly found?

Answer 56

a charge that builds up in one place and is not free to move - most common in insulators

Question 57

how can static charge be built up?

Answer 57

by friction as it strips electrons off one material and places them on the other meaning one material is positively charged and the other negatively charged