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a level physics > Electricity > Flashcards

Electricity Flashcards

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1
Q

what is current

A

the rate of flow of charge

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2
Q

what is potential difference

A

the work done per unit charge between 2 points

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3
Q

what is 1 coulomb

A

the amount of charge that passes in 1 second when the current is 1

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4
Q

what type of circuit must the ammeter be attached to get a current reading

A

An ammeter must always be attached in series

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5
Q

what type of circuit must a voltmeter be attached to get a voltage reading

A

It must be attached in parallel

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6
Q

what is potential difference between 2 points

A

The amount of work done moving charge between those points

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7
Q

what is resistance

A

How difficult it is for current to pass through

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8
Q

What is ohms law

A

current is directly proportional to the voltage across it

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9
Q

what are ohmic conductors

A

conductors that follow ohms law

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10
Q

When does Ohms law become true for components

A

When constant physical factors such as temperature and light remain constant

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11
Q

what does an I-V graph of an ohmic conductor look like

A

straight line graph going through the origin

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12
Q

what does a lower gradient of a I-V graph mean

A

there is a greater resitscance

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13
Q

what is a rheostat

A

a variable resistor used to control current

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14
Q

what is the resistance of a voltmeter

A

infinite resistance

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15
Q

what is the resistance of an ammeter

A

0/no resistance

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16
Q

how does heat effect resistance

A

the particles vibrate more at higher temperatures which makes it harder for electrons to move through the wire

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17
Q

What are diodes

A

Semi-conductors that only let current flow in one direction

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18
Q

What is forward

A

The direction in which current is allowed to flow

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19
Q

What is the threshold voltage i

A

The voltage required for diodes to allow current to flow. (It is normally 0.6V)

20
Q

Is a filament lamp an ohmic conductor

A

No it isnt

21
Q

How can you tell what is or is not an ohmic conductor

A

The I-V graph needs to be a straight line. If the graph is not a straight line then it is not an ohmic conductor

22
Q

what is resistivity

A

It is a measure how much a particular material resists current flow

23
Q

what is the difference between resistance and resistivity

A

Resistivity is how much a MATERIAL resists current flow whilst
Resistance is how much an OBJECT resists current.

resistivity is a property of a material while resistance is the property of an object.

24
Q

What is a semi-conductor

A

It is a material that doesnt conduct electricity as good as metals because they have fewer electrons

25
Q

what are 3 common semi-conductor

A

-thermistor
-diode
-LDR`

26
Q

what is a thermistor

A

It is a component where is the temperature is higher the resistance is lower. This is because higher temperature means more electrons escape from their atoms so there will be more charge carriers

27
Q

what is a LDR

A

It is a light dependent resistor which means the more light the lower the resistance.

28
Q

What is a superconductor

A

A conductor which has 0 resistance

29
Q

How can you make a super conductor

A
  • By reducing the temperature you can lower the resistance till eventually you get 0 resistance
30
Q

what is traditional temperature

A

It is the critical temperature that needs to make a superconductor.

31
Q

What are 2 uses of a superconductor

A
  • power cables
  • creating a strong magnet for medicinal uses
32
Q

what is power

A

The rate of energy transfer

33
Q

What is the equation for energy transfer without using power

A

E = IVt

energy transfer = current x voltage x time

34
Q

What is internal resistance

A

The resistance inside of a battery

35
Q

What is e.m.f

A

It it the energy transferred to each electron. e.m.f is measured in volts

36
Q

What is load resistance

A

The total external resistance in a circuit (this does not include internal resistance)

37
Q

What is terminal p.d

A

The energy transferred when one coulomb of charge flows through the load resistance

38
Q

what is lost volts

A

The energy lost in overcoming the internal resistance

39
Q

what is the equation for e.m.f with lost volts

A

e.m.f = lost volts+ terminal p.d

40
Q

what is kirchoffs first law

A

current entering a junction is equal to current leaving a circuit

41
Q

what is kirchoffs second law

A

the total e.m.f is equal to all the p.d of all the components

42
Q

how do you calculate the total e.m.f of cells in series

A

You add the e.m.f of all the cells together

43
Q

how do you calculate the total e.m.f of all cells in parallel

A

The total e.m.f is the same as the e.m.f of one cell

44
Q

what are potential divider circuits

A

circuits which produce an output voltage as a fraction of their input coltage

45
Q

what are the 3 main reasons for using a potential divider

A
  • to produce a varying potential difference
  • to be able to choose a specific potential difference
  • to split the potential difference between two components
46
Q

what is the equation for a potential divider

A

Vout = (R2/(R1+R2))Vin

47
Q

what happens when you switch a fixed resistor with a variable resistor like a thermistor

A

the output voltage will vary

a level physics (4 decks)

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