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Electricity Flashcards

1
Q

electric current definition

A

the rate of flow charge

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2
Q

direction of current flows from..

A

the positive terminal to the negative terminal

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3
Q

link the equation involving, charge, current and time

A

Charge (C)= Current (A) x Time (s)

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4
Q

how do you meassure current

A

ammeter

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5
Q

how to connect ammeter

A

in series so all the charge flows through it

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6
Q

potential difference definition

A

the amount of energy transferred per unit of charge passing through the terminals

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7
Q

1 volt is equal to __

A

one joule

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8
Q

potential difference equation

A

V = energy transferred/ charge moved

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9
Q

how is potential difference measured

A

voltmeter

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10
Q

how are voltmeters connected

A

in parallel

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11
Q

why do voltmeters have to be connected in 2 points of circuit

A

as it needs to calculate the difference

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12
Q

resistance

A

opposition to current

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13
Q

the higher the resistance =?

A

the lower the current

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14
Q

do good conductors have low or high resistance

A

low

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15
Q

symbol for resistance

A

R

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16
Q

how is resistance measured

A

ohms (one volt per ampere)

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17
Q

equation linking voltage, current and resistance

A

potential difference= current x resistance

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18
Q

how is current in a series circuit

A

the same value at any point

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19
Q

what does the amount of curent flowing in a series circuit depend on

A
  • voltage
  • number of components in circuit
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20
Q

increasing voltage=

A

increase in current

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21
Q

what happens in a juction where 2 or more wires meet

A

the current is always split at a circuit junction

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22
Q

is current and charge conserved

A

yes

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23
Q

voltage in a series circuit

A

shared between the components
- the voltage across components is the same

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24
Q

advantages of series circuit

A
  • all components are controlled by a single switch
  • fewer wires are required
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25
disadvantages of series circuit
- components cannot be controlled separately - if one component breaks they all stop working
26
what does a parallel circuit consist of
2 or more components attached across different branches of the circuit,
27
advantages of parallel circuis
- invidually controlled - even if one breaks, others function
28
disadvantages of parallel circuits
- more wires involved - all components have the same v supply, so harder to control.
29
resistors in series
the total resistance is equal to the sum of their individual resistance
30
potential difference and current are ------------
porportional
31
current through a fixed resistor
increases as the potential difference increases
32
filament lamp, current and voltage relationship
not directly proportional
33
why is the relationship in a filament lamp,current and voltage not directly proportional
resistance of a filament lamp increases as the temperature of the filament increases
34
diodes- foward bias
allow current to flow in one direciton only
35
diode - reverse bias
the diode has high resistance so no current flows
36
2 types of resistors
- fixed resistor - variable resistor
37
fixed resistors
resistance that remains constant
38
variable resistors
can change the resistance by changing the length of the wire that makes up the circuit .
39
thermistors
temperature-dependent resistor - higher temp= resistance decreases
40
LDRs
more light intensity= resistance of LDR decreases
41
lamps
illuminate when a current flows in a circuit
42
LEDs
types od diodes, only lights up if the current passes in that direction
43
power
the rate of energy transfer per second
44
power equation
power (W) = current x voltage
45
fuse
cuts off the flow of electricity to an appliance if the current becomes too large
46
what happens to a fuse if the current is too large
wife heats up and melts, causes wire to break and stop the circuit
47
work
when charge flows through a circuit
48
work done
equal to energy transferred
49
what does the amount of energy transferred by electrical work in a component depend on
- current - voltage - amount of time
50
energy transferred equation
E= P (w) x t
51
common hazards in electricity
- damaged insulation - overheating of cables - damp conditions
52
safety features which are built into domestic appliances
- double insulation - earthing - fuses - circuit breakers
53
double insultation
- insulation around the wires themselves - a non metallic case that acts as a second layer of insulation
54
earthing
- provides a low resistance path to the ground - no resistance a large current can flow
55
what occurs if there is a malfunction in current
- earth wire provides a low resistance path to the groudn - it casegrounds a surge of current in the earth wire and live wire - high current through the fuse causes it to melt and break - cuts off the supply of electricity.
56
what do fuses consist of
glass cylinder containing a thin metal wire
57
circuit breaker
automatic electromagnet switch that breaks circuit if the current exceeds a certain value
58
advantage of circuit breaker
- doesn't melt so it can be reset and used again - works much faster
59
what happens when electricity passes through a component
some of the energy is transferred to heat, increasing the temp
60
why is energy transferred
as a result of collisions between - electrons flowing in a conductor - lattice of atoms within the conductor
61
direct current
- current that is steady, and constantly flowing in same direction in a circuit from + to -
62
what produces a direct current
electrical cells or batteries
63
alternating current
- current that continuously changes its direction going back and forth aroud a circuit
64
frequency of an alternating current
number of times the current changes direction in a second
65
conductor
material that allows charge to flow through it easily
66
conductor examples
steel, copper, aluminum, silver
67
what are conductors made up of on the atomic scale
positively charged metal ions with their outermost electrons delocalized.
68
insulator
material that has no free charges so it does not allow the flow of charge through them very easily
69
insulator examples
rubber, plastic, glass
70
what type of electricity do insulators conduct
static electricity.
71
charging by friction
when insulating materials are rubbed against one another, they become electrically charged
72
rubbing a polythene rod and cloth together
- electrons transfer from the cloth to the rod, so the rod gains electrons, - the cloth is then positively charged
73
attraction of atoms
positive and negative
74
repulsion of atoms
negative and negative positive and positive
75
uses of static electricity
photocopiers insecticise sprays
76
what is the danger of static electricity
sparking, risk of electrocution.
77
how do you prevent the risk of sparking
earthing

Physics (6 decks)

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