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Physics > 3. Electricity > Flashcards

3. Electricity Flashcards

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1
Q

Protons and neutrons are examples of what

A

Nucleons

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2
Q

Absolute charge of electron in coulombs is

A

-1.6x10^-19C

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3
Q

How many electrons are in 1C

A

6.25x10^18 electrons

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4
Q

Relative mass of electrons

A

1/2000

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5
Q

If you have a 9v battery every coulomb of charge gets how much energy

A

9 joules

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6
Q

Potential difference is what

A

Energy that has been transferred by each coulomb of charge

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7
Q

Potential difference formula

A

V=E/Q. E is energy and q is charge

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8
Q

PD of 1v means each coulomb transfers how much

A

1J

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9
Q

Resistor networks

A

Groups of resistors to make an equivalent resistance

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10
Q

Resistance total formula in parallel

A

R total=R1+R2+R3
E.g. 1/R1+1/R2+1/R3
Then find reciprocal

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11
Q

Charge

A

A physical property of matter that causes it to experience a force when placed in and EM field

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12
Q

Current

A

Rate of flow of charged particles, defined by charge per unit time

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13
Q

Potential difference

A

Difference in energy stored per unit charge between two points

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14
Q

Resistance

A

An object property that opposes flow of charge

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15
Q

Work done

A

Energy transferred as matter is moved a distance against a force

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16
Q

Avagrado constant

A

6.02x10^-23

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17
Q

Emf

A

Electromotive force

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18
Q

Current equation

A

I=change in charge/change in time

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19
Q

Electromotive force

A

Supply / component which is putting electrical energy into a circuit.

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20
Q

Correct term of voltage

A

EMF

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21
Q

Voltage

A

Amount of energy a component transfers per unit

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22
Q

Voltage equation/emf/pd

A

Voltage =energy transferred / charge passing

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23
Q

Electron volt

A

Unit of energy that is generally used with sub atomic particles comes from equation V=E/Q

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24
Q

Current in series circuit

A

Same current all the way through

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25
Q

Current in parallel circuit

A

Splits across circuit

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26
Q

Voltages in series

A

Splits and adds up back to supply

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27
Q

Voltage in parallel

A

Identical voltage across branches

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28
Q

Resistance equation in series

A

Rtotal=R1+R2+R3

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29
Q

Ohmic conductor

A

Component through which the current is proportional to the voltage it is

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30
Q

Material property (resistivity,brittleness ,tensile strength and hardness)

A

Doesn’t depend on dimensions only what it’s made of

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31
Q

Object property (resistance ,breaking force )

A

Depends on the materials as well as dimensions and constructions

32
Q

Difference between resistance and resistivity

A

Resistance depends on amount of something and resistivity depends on composition

33
Q

What affects resistance in objects

A

Area-narrow means less space to flow
Length-long means will be harder to get through
Type of material (resistivity)

34
Q

Resistance equation

A

R=pL/A
Resistance =resistivity x length/area

35
Q

Resistivity

A

Materials ability to resist flow of charge. Materials of low resistivity are chosen for conducting circuits (gold etc)

36
Q

Drift velocity is always _______than electron speed

A

Slower

37
Q

Transportation equation

A

I=NAvQ
N-electron density
A-cross section area
V-drift velocity
Q-charge of electrons

38
Q

Semiconductors got what

A

Lower electron density meaning few electrons are free to drift

39
Q

Conduction bands

A

Allow charge to flow across the structure when a potential difference is applied.

40
Q

Structure of semiconductor

A

Single atoms have electrons orbiting in shells.
Adding energy will increase the level the electrons can reach then ionising the atom when the electron is free to leave.
Atoms combine to form giant lattice the energy levels act in different way
Some energy levels are still possessive to the atom.

41
Q

Ohms law

A

Current through conductor is directly proportional to PD across it( if temperature and external environment remain the same)

42
Q

Non ohmic conductor

A

Current through component affects its own temperature

43
Q

What is the tool used to measure diameter of a wire

A

Micrometer

44
Q

What is drift velocity

A

Slow overall moment of electrons

45
Q

A slight decrease in N for metals at higher temperatures is due to what

A

Thermal expansion

46
Q

Semiconductors

A

Generally solid materials that only have small numbers of delocalised electrons that are free to conduct
E.g silicon

47
Q

How are energy bands formed

A

Whether there are many atoms close together, they allowed energy levels become much wider, forming energy bands

48
Q

Valence band every level

A

Electrons of this amount of energy remain highly to atoms and do not form part of any electric. Current, those are gain energy to jump up to the conduction band they can delocalised and can move through the part of a current. 

49
Q

Number of delocalised electrons in a semiconductor is____than metals for the same applied voltage.

A

Lower

50
Q

What happens when an electron enters a conduction band and moves away

A

Leaves the atom with an effective positive charge

51
Q

An insulator has what type of bands

A

Empty, conduction band and full valance band

52
Q

A semiconductor has what type of bands

A

Almost empty, conduction bands and almost full valance band 

53
Q

A metal has what type of bands 

A

Almost full conduction band and valance band 

54
Q

The empty space electron has left is referred to as what 

A

Positive hole 

55
Q

What is known for a few charge carriers can pass at low voltages 

A

Leakage current 

56
Q

What are insulators? 

A

Materials in which the energy gap between the valance band and the conduction band is so large, there are virtually zero electrons available for conduction 

57
Q

Resistance increases with high temperatures how

A

The higher level of internal energy in the material causes more vibration of the fixed irons, and these collide more often the charge carriers to reduce their speed of movement through the material. Reduce the temperature therefore reduce resistance, allowing greater current flow. 

58
Q

Below a certain critical temperature, what happens to the resistance?

A

Resistance suddenly drops to 0, this is called superconductivity 

59
Q

What is superconductivity?

A

Resistance drops to 0, because it reaches a critical temperature 

60
Q

Difference between PD and EMF

A

PD is electrical energy transferred between two points , or the electrical energy transformed or converted to other forms
EMF is the energy supplied to a circuit

61
Q

Kirchhoff rule 1

A

Total current entering a junction is equal to total current leaving it
Current is conserved

62
Q

Kirchhoff law 2

A

In any closed loop network the total emf is equal to the sum of p.d drops

63
Q

Potential divider equations with V

A

V1/R1 =v2/R2

V1/v2=R1/R2

64
Q

Potential divider equation

A

V out=v in x R2/R1 +R2

65
Q

Potentiometer

A

Version of the potential dividing which is single resistance. Wire is used in two parts to form material resistances a sliding connection on the wire can be adjusted to alter the comparative resistances as fast out of output PD from the potential meter.

66
Q

NTC

A

Negative temperature coefficient

67
Q

Potential divider in sensor circuit

A

Lamp is in parallel with LDR, so will be powered by the same voltage as that across the LDR

68
Q

Potential divider

A

Circuit designed to provide specific voltage values by splitting an EMF across two resistors

69
Q

Internal resistance

A

Resistance of an emf source

70
Q

Internal resistance on graph

A

Negative gradient slope

71
Q

EMF on graph

A

Y intercept

72
Q

Effect of having an internal resistance

A

EMF will never be able to fully supply it’s notional maximum voltage They always be a small drop in voltage over the entire resistance, and this drop will be bigger with a higher current. 

73
Q

Power

A

Rate of transfer of energy or rate of doing work

74
Q

Expression for Current in terms of emf

A

I=emf I(R+r)

75
Q

What happens to the PD across the thermistor as temperature increases?

A

As temperature increases number of free charge characters and faster increase so resistance decreases faster resistance as a proportion of total resistance decreases PD across thermistor decreases

76
Q

Using an ammeter with non-resistance but is affected by using for me with a lower resistance. Explain why 

A

Ammeter
If family has resistance currently decreased, but doesn’t affect the determination because current through cell is measured

Or doesn’t affect whether the determination because of a measure is the terminal PD for that current?

Voltmeter
Vote me has smaller resistance. It would draw current measured current not current through cell

Physics (8 decks)

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