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GCSE Physics OCR A > P3 > Flashcards

P3 Flashcards

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1
Q

How do object become charged?

A

Transferring electrons, with the force of friction

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2
Q

What are fields?

A

A region within which object experience a force

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3
Q

What is essential for the three fields?

A

Gravitational = needs mass
Magnetic = needs anything with magnetic properties
Electric = needs a charged object

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4
Q

What way do electric field lines go?
(electrostatic)

A

Leave positive and enter negative

Positive is the long wire, negative is the short

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5
Q

What do charge objects experience in an electric field?

A

Repulsion or attraction

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6
Q

What is current?

A

The rate of flow of charge, how many electrons pass a point in a second

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7
Q

What is the formula for current?

A

I = Q➗ T
I= amps
Q= coulombs
T= seconds

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8
Q

What is the symbol for a diode?

A

A circle with a triangle , line at the end pointing in the direction of current

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9
Q

What is the symbol for an LEd

A

The symbol of a diode with two arrows coming out of the circle

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10
Q

What is the symbol for a fixed resistor?

A

A solid rectangle

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11
Q

What is the symbol for a variable resistor, what does it do?

A

A solid rectangle with an arrow going diagonally though

Vary the resistance, and the current and p.d

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12
Q

What is the symbol of a fuse?

A

A rectangle with a line going through

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13
Q

What is the symbol for a heater?

A

A solid rectangle cut into boxes

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14
Q

How much charge does an electron carry?

A

1.6 ✖️10^-19 coulombs

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15
Q

What is voltage?

A

The measure of energy per charge
V= E/ Q

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16
Q

What is potential difference?

A

Difference in voltage between two points

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17
Q

What is the equation for potential difference? (Energy)

A

V = W➗Q
V= potential difference ,v
W= work done, J
Q= charge , C

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18
Q

What is resistance?

A

The opposition to the passage of charge (current)

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19
Q

How does temperature affect resistance?

A

The more kinetic energy the positive ions have the more they vibrate up and down. Stopping them flow, reducing current.
The greater the temperature, the greater resistance

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20
Q

Why does current transfer energy in a circuit?

A

Resistance, the higher the resistance, the more energy is transferred by the current

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21
Q

What is the main equation for potential difference?

A

V=I ✖️R
V= pd, volts
I= current , amps
R= resistance, ohms

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22
Q

What is charge?

A

A property of matter ,
Electrons carry charge

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23
Q

What is a series circuit?

A

The electrons must travel through every component,
Just one loop, no branches

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24
Q

How does the current differ in a series circuit?

A

It stays the same throughout
It=I1=I2

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25
Q

How does the voltage differ in a series circuit?

A

The total voltage is shared throughout the circuit
Vt=V1+V2

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26
Q

How does resistance differ in a series circuit?

A

It’s shared out throughout the circuit
Rt=R1+R2

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27
Q

What is a parallel circuit ?

A

The electrons do not travel through the same components.
The circuit has branches

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28
Q

How does current differ in a parallel circuit?

A

It distributed between each branch
It= I1+I2

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29
Q

How does potential difference differ in a parallel circuit?

A

It is the same across each branch
Vt = V1 =V2

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30
Q

How does resistance differ in a parallel circuit?

A

1/Rt= 1/R1 + 1/R2

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31
Q

What p.d is required to create 1A?

A

100 kw
Therefore it is very unlikely that you’d be injured by an electrical currents

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32
Q

What is the gradient of an I-V graph ?

A

1/R
Opposite of resistance

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33
Q

What is ohms law?

A

The current through a component is directly proportional to the potential difference, as along as the temperature is kept constant

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34
Q

What does a diagonal straight line show on an IV graph?

A

Constant resistance

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35
Q

What does a steep gradient show on an IV graph?

A

low
resistance

36
Q

What does a shallow gradient show on an IV graph?

A

high resistance

37
Q

Explain why as the p.d increases , the component gets hotter?

A

Some of energy transferred as the electrons pass through the component (voltage).
more energy transferred per coulomb of charge
Some of this energy is transferred to heat

38
Q

What pattern do fixed resistors follow on an IV graph

A

🔺Diagonal straight line (linear circuit element) - resistance is constantly
🔺Ohmic conductors (follows Ohm’s law)

39
Q

How can you note temperature in an IV graph

A

As the p.d is increasing, so is the temperature

40
Q

Describe the IV graph for a filament light bulb

A

🔺The resistance increases with p.d
🔺As the resistance increases as it is getting hotter
🔺Non - linear circuit element

41
Q

Describe the IV graph for a diode

A

Forwards resistance is low
Reverse resistance is high

42
Q

How does the net resistance change when you add more resistors in a series circuit?

A

The net resistance increases as the total current decreases

43
Q

How does the net resistance of a parallel circuit change when you add more resistors?

A

The net resistance decreases, and will always be smaller than the resistance of the smallest resistance branch
The total current increases

44
Q

What is a sensor circuit?

A

A circuit that turns a component on or off automatically in response to external stimuli

45
Q

What is a thermistor?

A

A type of resistor who’s resistance in reduced greatly by heating
Inverse temp and resistance

46
Q

Describe how a thermistor works

A

🔘in series with a fixed resistor and in parallel with a component
🔘as temperature decreases, resistance increases (more than the fixed resistor)
🔘as ratio of shared resistance increases so does the shared p.d
🔘as in parallel with the component the p.d also increases at it is the same
🔘once voltage is high enough the working potential is reached and it is switched on

47
Q

How would you calculate sensor circuits

A

Use ratios and assume the same ratio for P.d as resistance ratios

48
Q

What is electrical power?

A

The rate of electrical energy transfer
Joules per second

49
Q

What is the formula for electrical power?

A

P=I ✖️V
P=Watts
I= amps
V= volts

50
Q

What is the equation for electrical power(2) ?

A

P = I^2✖️R
P= watts
I= amphs
R=ohms

51
Q

What are watts a measures of?

A

The amount of joules transferred in a second

52
Q

What is a diode?

A

A semi- conduct that allows current to flow easily in one direction, but restricts it in the other

53
Q

What is an LDR ?

A

A light dependant resistor.
When the light intensity decreases, the resistance increases.

54
Q

Why does moisture decrease the build up of static charge?

A

Moisture can conduct charge, not allowing it to build up

55
Q

How does the amount of resistance wire affect the current?

A

The more the wire , the less the current
The less wire, the more current

56
Q

How is the relationship between temperature and p.d shown on a graph?

A

A curving gradient of resistance as p.d increases

57
Q

How is current calculated?
if given a certain amount of electrons

A

The number of electrons ✖️1.6*10^-19 coulombs

58
Q

What happens to the electrons when the current is doubled?

A

The amount of electrons present doubles

59
Q

What do the electrons look like in a wire with no current?

A

Electrons are present , but all are moving in random directions. They all chance, each other out with an overall 0 charge.

60
Q

How do thermistors decrease their resistance with increased temperature?

A

The ions vibrating faster < temperature releasing electrons from their shells- decreasing the resistance

61
Q

Why are their differences in voltage between the wires?

A

The cell/ battery creates chemical reactions which bunch up the electrons in places of the wire. So the electrons will travel from a high point to a low point , creating a p.d

62
Q

Why do the electrons travel from high voltage to low voltage?

A

Everything wants to have a lower energy state in the world.

63
Q

describe the relationship between current and resistance

A
64
Q

describe the relationship between temperature and resistance

A

Mention how it impacts current

65
Q

what are the conditions needs for charge to flow?

A
  • a source of potential difference
  • a closed circuit
66
Q

what does it mean to be neutral?

A

a zero net charge, an equal amount of positive chanrge as negative charge

67
Q

how do you produce static electricity?

A

rubbing 2 insulators together transfering electrons from onr to the other creating a positive and neative charge

68
Q

what is discharge?

A

(removing the charge)
connecting to something that allows charge to flow
like a metal

air can conduct electricity

69
Q

what are sparks?

A

a flow of charge or current through the air

70
Q

define current :

A

the rate of flow of charge (electrons)

71
Q

what are the conditions required for charge flow?

A
  • a closed circuit
  • source of potential difference
72
Q

compare series and parallel circiuts

A
  • in parallel if one branch/ component breaks don- then the rest of the circuit remains unaffected
73
Q

how do you measure current in series ?

A

place the ammeter anywhere within the circuit in series, it will have the same reading all around because current is the same in a series circuit

74
Q

how do you measure current in a parallel circuit?

A

since current is shared throughout each branch , place the ammeter in series for each branch and the total wll be the total current

75
Q

how do you measure potential difference in a series circuit ?

A

place the voltmeter in parallel (wire with both sides of the component )

76
Q

how do you connect an ammeter ?

A

Negative terminal next to negative terminal

77
Q

How do you measure the potential difference in parallel?

A

the voltmeter in parallel to the cell will be the same as the pd for each branch

78
Q

How do you get the lowest total resistance ?
(in parallel circuits)

A

The more components in parallel, the less Total resistance

79
Q

What side of the cell is negative and positive?

A
80
Q

Why would you use a resistor or a resistance wire ?

A

If you want the resistance to be constant

81
Q

What Is resistance ?

A

The collision of electrons with metal ions

82
Q

What is a linear circuit element ?

A

Resistance doesn’t change as the potential difference changes (constant resistance)

83
Q

How do thermistors decrease their resistance as temperature increases?

A

The semi conductor material allows electrons to escape from the atoms , producing current

84
Q

What happens when you add components to a series and parallel circuit?

A
85
Q

Where will there be more current (in a circuit) ?

A

Where less resistance is offered (less components)

GCSE Physics OCR A (13 decks)

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