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electricity Flashcards

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1
Q

potential difference

A

force driving the flow of electrons measured in volts

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2
Q

current

A

a measure of tmr flow of electrons around a circuit measured in amps

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3
Q

resistance

A

everything that resists or opposes the flow of electrons measured in ohms

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4
Q

what direction does the current flow (conventional current)

A

from the positive side to the negative side

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5
Q

what is the proportion between V and I

A

it is directly proportional

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6
Q

what happens to the resistance if the temp increases

A

the resistance increases

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7
Q

what happens to a filament lamp when it turns on.

A

to turn on, the wire gets so hot to the point where it emits light, this then increases temp, this increases resistance, that then makes the current decrease. this can be seen on a graph

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8
Q

diodes

A

allow current to flow only in one direction

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9
Q

what does a diode have

A

a very high resistance in tmr reverse direction, that’s why it only allows a current to flow in one direction

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10
Q

what’s the difference between an led and a diode

A

an led emits light when current flows whereas a diode doesn’t

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11
Q

charge

A

a measure of the total current that flowed within a certain period of time

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12
Q

what is the potential difference pattern in a series circuit

A

the pd is shared across all the components
V = V1 + V2 + V3

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13
Q

what is the pattern with current in a series ciruict

A

it remains the same everywhere

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14
Q

what is ohms law

A

V = I * R

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15
Q

what is the comparison between resistance and voltage in series

A

the greater the resistance, the higher the voltage share

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16
Q

How does the potential difference divide in a parallel circuit

A

It doesn’t divide, for each loop, there’s the same as the cell

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17
Q

How is the current shared

A

It is divided between the loops, from the main cell

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18
Q

What is the link between resistance and the number of components

A

The more the components, the lower the total resistance

19
Q

What do the loops that have a greater resistance take

A

A larger share of current

20
Q

How is an ammeter connected

A

In series

21
Q

How is a voltmeter connected

A

In parallel

22
Q

What happens to resistance in the dark of an led

A

It’s higher in the dark, hardly any current can flow

23
Q

Where can light dependent resistors be used

A

Automatic night lights
Burglar alarms

24
Q

Where are thermistors used

A

Car engines
Electronic thermostats

25
Q

What happens to a thermistor when temp increases

A

Resistance falls current increases

26
Q

What happens to a light dependent resistor when light intensity increases

A

Resistance falls, more current can flow

27
Q

Equation of power

A

P = V * I
power = voltage * current

28
Q

What does a step up transformer do

A

Increases the voltage from the power station

29
Q

Why can’t we use high current to transport energy from the national grid

A

As that would take up lots of heat due to the resistance and it would cause a lot of energy to be lost to surrounding.

30
Q

What do they increase instead of current to transmit electricity

A

High voltage

31
Q

What does a step down transformer do

A

Reduces the voltage back down

32
Q

Why is a step down transformer needed

A

To make sure that the voltage won’t blow household appliances and doesn’t cause danger

33
Q

What happens in an AC current

A

Direction of current swapping

34
Q

When do we get this AC

A

When we use an alternating potential difference

35
Q

What is static electricity

A

Build up of charge on insulated materials

36
Q

Why does static electricity not happen in conductive materials

A

As the electrons just swap and flow straight back again so no charge ever builds up

37
Q

Why do insulated materials gain static charge

A

As electrons can’t flow back

38
Q

What happens between a polythene rod and cloth

A

The electrons are transferred from cloth to rod, leaving rod gaining negative charge

39
Q

What happens between acetate rod and cloth

A

Electrons are transferred from rod to cloth, leaving the rod positively charged due to loss of electrons

40
Q

Why does a spark happen

A

More electrons are transferred between charged material and size of charge increases, potential difference is developed, if the pd between charged object and earth object is large enough, electrons can jump across the gap and this causes a spark

41
Q

Rules in series

A
  • I is same everywhere
  • total V is shared
42
Q

Rules for parallel

A
  • V is same everywhere
  • current is divided between loops
43
Q

Resistance total in Series vs parallel

A

Series:
R1+R2

Parallel:
1/R1 + 1/R2

physics continue (6 decks)

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