Section 6 - Electricity Flashcards

1
Q

Current def

A

Rate of flow of charge

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2
Q

I, Q, T formula

A

Q = It

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3
Q

Direction of current flow

A

+ to -

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4
Q

Unit of charge

A

Coulomb (C)

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5
Q

Coulomb def

A

One coulomb is the amount of Charge that passes in 1 second if the charge is 1 Amp

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6
Q

Potential Difference def

A

Work done per unit charge moved

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7
Q

Voltage f

A

v = W/Q (Word done/charge)

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8
Q

Voltage in components connected in a parallel

A

The same

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9
Q

Current in components connected in a parallel

A

Shared

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10
Q

Voltage in components conected in series

A

Shared

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11
Q

Current in components connected in seres

A

The same

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12
Q

How must a voltmeter be connected

A

in parallel with the component

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13
Q

Definition of a volt

A

1 volt is when you convert 1 joule of energy moving 1 coulomb of charge through a component

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14
Q

Resistance f

A

R = V/I

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15
Q

Resistance def

A

A measure of how difficult it is for current to flow through a component

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16
Q

Ohmic conductor def

A

A conductor for which |R is constant

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17
Q

Ohms law

A

Provided the physical conditions, such as temperature, remain constant, the current through an ohmic conductor is directly proportional to the current across it

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18
Q

Graph for an ohmic conductor

A

Straight line graph passing through (0,0)

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19
Q

Circuit to obtain an I/V graph

A

INsert pic

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20
Q

I/V graph for a filament lamp

A

INsert pic

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21
Q

I/V characteristic for a filament lamp

A

The resistance of a metal increases as the temperature increases

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22
Q

Semiconductors

A
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23
Q

Thermistor def

A

A resistor with a resistance that depends on temperature

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24
Q

NTC thermistor

A

Negative temperature coefficient
Resistance decreases as temperature goes up

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25
Q

Filament lamp symbol

A

Pic

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26
Q

Thermistor symbol

A

Pic

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27
Q

NTC thermistor I/V graph

A

Pic

28
Q

How a NTC thermistor works

A

Warming the thermistor gives more electrons enough energy to escape from their atoms, this means that there are more charge carriers available so the resistance is lower`

29
Q

Diodes def

A

Components that only allow current to flow in one direction

30
Q

Diode Symbol

A

Pic

31
Q

LED symbol

A

Pic

32
Q

Forward bias def

A

The direction in which a diode allows current to flow

33
Q

Three things that determine resistance

A
  • Length of wire (l)
  • Cross sectional area of a wire (A)
  • Resistivity ((P))
34
Q

Resistivity def

A

The resistivity of a material is defined as the resistance of a 1m length with corss sectional area 1m^2

35
Q

Resistivity units

A

Ohm-metres`

36
Q

Resistivity formula

A

RA/l

37
Q

Experiment to find the resistivity of a wire

A
38
Q

Superconductors def

A

Materials with zero resistance

39
Q

Power def

A

The rate of transfer of energy

40
Q

Unit of power + def

A

Watts: 1 joule per second

41
Q

Power formla

A

P = E/t

42
Q

3 formulae for power in a electrical circuit

A

P = VI
P = (v^2)/R
P = (I^2)R

43
Q

What causes resistance

A

Resistance comes from electrons colliding with atoms and losing energy to other forms

44
Q

Internal resistance def

A

The resistance to the flow of charge within a power source such as a battery

45
Q

Load resistance

A

The total resistance of all components in the external circuit

46
Q

EMF def

A

The amount of electrical energy the battery produces for each collumb of chargeE

47
Q

EMF full form

A

Electromotive Force

48
Q

EMF unit

A

VOlts

49
Q

EMF formula

A

EMF = E/Q

50
Q

Terminal PD def

A

The potential difference across the load resistance, the energy transferred when one coulomb f charge flows through the load resistance

51
Q

What would happen if there was no internal resistance

A

The terminal PD would be the same as the EMF

52
Q

Lost volts def

A

The energy wasted per coulomb overcoming the internal resistance

53
Q

Conservation energy

A

Energy per coulomb supplied by the source
=
Energy per coulomb transferred in load resistance
+
Energy per coulomb wasted in internal resistance

54
Q

4 formulae with EMF and internal resistance

A

Pic

55
Q

EMF of cells in series

A

Et = E1 + E2 +E3 …

56
Q

EMF of cells in parallel

A

Et = E1 = E2 = E3 …

57
Q

Investigating Internal resistance and EMF circuit

A

Pic

58
Q

Investigating internal resistance and EMF steps [3]

A
  • Vary the current in the circuit by changing the vaue of theload resistance(using the variable resistor).
  • Measure the PD for several values of current
  • Record the results and plot a graph of v against I
59
Q

Calculating internal resistance and MEF from a V-I graph

A

Pic

60
Q

Kirchhoff’s fist law

A

Conservation of charge
The total current entering a junction = the total current leaving it

61
Q

Kirchhoff’s second law

A

Conservation of energy
The total EMF around a series circuit = the sum of the PDs across each component

62
Q

Adding resistance in series

A

Rt = R1 + R2 +R3 …

63
Q

Deriving how resistance is added in series

A

Pic

64
Q

Adding resistance in Parallel

A

1/Rt = 1/R1 + 1/R2 + 1/R3 …

65
Q

Deriving how resistance is added in series

A

Pic

66
Q
A