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Physics - Paper 1 > P3.2 > Flashcards

P3.2 Flashcards

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1
Q

What is voltage

A

Voltage is a measure of the energy carried by the current (per coulomb of charge)

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2
Q

What is potential difference

A

Potential difference (P.D) is the difference in (Potential Energy) voltage between two points.

OR

Potential difference is a measure of thework done per coulomb of charge.

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3
Q

Potential difference formula

A
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4
Q

What does the potential difference across a component indicate

A

how much energy was transferred by the current as it passed through the component.

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5
Q

What component measures potential difference

A

Voltmeter

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6
Q

What is resistance

A

Resistance is the opposition to the passage of charge.

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7
Q

Where does resistance come from

A

In a wire/component, ions vibrate up and down.These vibrating ions will get in the way of the passing electrons, stopping them from flowing… reducing the current.The faster the ions vibrate (the hotter the wire) or the bigger the ions, the greater the resistance encountered, and the smaller the current flowing.

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8
Q

The higher the resistance…

A

the more energy transferred by the current as it passes through the resistance.

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9
Q

Resistance formula

A
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10
Q

What is a series circuit

A

is one in which the charge must travel through every component.

Has no branches = all one loop

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11
Q

Current in a series circuit

A

The current through every component in a series circuit is the same.

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12
Q

Resistance in a series circuit

A

The total resistance in a series circuit is the sum of all the component resistances.

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13
Q

Potential difference in a series circuit

A

The p.d. across components in a series circuit is shared out…… the greater the resistance of the component…… the greater the share of the total p.d. it has across it.

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14
Q

What is a parallel circuit

A

A parallel circuit is one in which the charge doesn’t travel through the same components.
HAS BRANCHES

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15
Q

Potential difference in a parallel circuit

A

The p.d. across components in a parallel circuit is the same.

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16
Q

Resistance in a parallel circuit

A

The total resistance in a parallel circuit isNOT THE SUM of all the component resistances.(less than smallest resistance in circuit; don’t have to know how to calculate at GCSE)

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17
Q

Current in a parallel circuit

A

The current in a parallel circuit is split between components/branches.

… the greater the resistance of the component…… the less current through it.

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18
Q

What does the gradient of an IV graph represent

A

1
—
R

The gradient of an I-V graph is 𝐈/𝐕… this is the reciprocal of 𝐕/𝐈.

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19
Q

A steep gradient on an IV graph means…

A

Small resistant

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20
Q

A shallow gradient on an IV graph means

A

Large resistance

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21
Q

What is ohms law

A

The current through a component is directly proportional to the potential difference across it, as long as the temperature is kept constant.

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22
Q

What does a variable resistor do

A

Varies CURRENT

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23
Q

As the potential difference increases across a component…

A

The component gets hotter

24
Q

Fixed resistor IV graph

A
25
Q

What are wires/fixed resistors also known as

A

Ohmic conductors

26
Q

Filament light bulb IV graph

A
27
Q

Describe + explain the IV graph for a filament light bulb

A

As P.d increases, increase the current

More current in the filament lamp heats the positive ions

Ions vibrate faster and this opposes the transfer of charge in the filament lamp

Resistance increases

28
Q

Diode IV graph

A
29
Q
A
30
Q

What are thermistors

A

Thermistors are components (resistors) whoseresistance depends upon temperature.

31
Q

Resistance in thermistors

A

Resistance decreases as the temperature increases.

OPPOSITE TO NORMAL

32
Q

Why don’t thermistors behave like regular components ie. Why is their resistance trend opposite

A

due to the fact they are made of a special type of material, semiconductors.

33
Q

How does a thermistor work

A

As you heat a thermistor/semiconductor…

Ions vibrate faster – fewer electrons move through the wire per unit time.(the only thing that happens inside regular components)

More electrons are liberated from atoms of the semiconductor – more electrons move through the wire per unit time.(this effect is more pronounced than #1, so current increases, effectively meaning resistance must have decreased).

34
Q

What is an LDR

A

LDRs (light dependent resistors) are components (resistors) whose resistance depends upon light intensity.

35
Q

Resistance in LDRs

A

Resistance decreases as the light intensity increases.

OPPOSITE TO NORMAL

36
Q

How does LDRs work

A

As you give an LDR/semiconductor morelight energy…

Ions vibrate faster – fewer electrons move through the wire per unit time.(the only thing that happens inside regular components)

More electrons are liberated from atoms of the semiconductor – more electrons move through the wire per unit time.(this effect is more pronounced than #1, so current increases, effectively meaning resistance must have decreased).

37
Q

Suggest why the graphs of resistance against temperature, and of resistance against light level, eventually level off.

A

Resistance in thermistors and LDRs is primarily determined by the number of free electrons.

Increasing temperature and levels of light increase the number of free electrons.

Eventually after a certain amount of heat/light energy, all electrons will have been liberated, and resistance will no longer change with increasing temperature/light.

38
Q

If you add more resistors to a parallel circuit, what happens to the net resistance

A

Decreases

39
Q

How do sensor circuits work

A
  1. A fixed resistor of resistance R1 is connected in series with a thermistor of resistance R2.
  2. The p.d. of the battery is shared out amongst the fixed resistor and the thermistor(most dropped across highest resistance)
  3. The thermistor is connected in parallel with a component (eg – heater), the p.d. across both is VOUT.
  4. As the temperature in house decreases,resistance of thermistor, R2 increases.
  5. The p.d. dropped across the thermistor,VOUT, increases.
  6. Once VOUT increases to a high enough level,the “working potential” of the heater is reached and it switches on.
40
Q

Power Formula

A
41
Q

What is power

A

The rate of energy transfer

42
Q

Electrical power formula

A
43
Q

Electrical power formula - if you don’t know voltage (V)

A
44
Q

What is DC

A

A current that is steady, constantly flowing in the same direction in a circuit, from positive to negative

45
Q

What is AC

A

A current that continuously changes its direction, going back and forth around a circuit

46
Q

Frequency of AC

A

number of times the current changes direction back and forth each second

47
Q

Graph of DC

A
48
Q

Graph of DC

A
49
Q

Comparing AC & DC

A
50
Q

Define electric field

A

A region where an electric charge experiences a force

51
Q

Insulators vs conductors

A

Conductors allow charge carriers to freely move. Insulators do not allow charge carriers to move.

52
Q

Good conductors

A
53
Q

Good insulators

A
54
Q

Two types of thermistors

A

NTC and PTC

55
Q

What is NTC

A

negative temperature coefficient - have a lower resistance when the temperature increases

56
Q

What is PTC

A

positive temperature coefficient - thermistors have a higher resistance when the temperature increases

Physics - Paper 1 (8 decks)

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