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Physics > P4.2 - Electrical Quantities > Flashcards

P4.2 - Electrical Quantities Flashcards

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1
Q

What’s the relationship between positive and positive charges? [1]

A

they repel

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2
Q

What’s the relationship between positive and negative charges? [1]

A

they attract

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3
Q

What’s the relationship between negative and negative charges? [1]

A

they repel

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4
Q

What happens to the force the closer the charges are? [1]

A

the greater the force between them

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5
Q

Where do charges come from? [1]

A
  • when two materials are rubbed together
  • electrons may be transferred from one to another
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6
Q

What are the charges of the materials being rubbed together? [2]

A
  • one has a net negative charge
  • one has a net positive charge
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7
Q

What are conductors? [1]

A
  • materials that let electrons pass through them
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8
Q

What are the best electrical conductors? [1]

A
  • metals
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9
Q

What makes ___ good thermal conductors and why? [2]

A
  • metals
  • because they have free electrons
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10
Q

What are insulators? [1]

A
  • materials that hardly conduct at all
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11
Q

Why don’t insulators conduct? [2]

A
  • electrons are held tightly to their atoms
  • not free to move
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12
Q

How can electrons be transferred? [1]

A

by rubbing - static charging

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13
Q

What are examples of insulators? [3]

A
  • plastics
  • glass
  • PVC
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14
Q

What are semi-conductors? [1]

A

neither an insulator or a conductor

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15
Q

What are the properties of semi-conductors? [2]

A
  • poor conductors when cold
  • better conductors when warm
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15
Q

What is charge measured in? [1]

A

Coulombs

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16
Q

What is Static Electricity? [2]

A
  • charges which are not free to move
  • charges are at rest
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17
Q

What does the charging of solids by friction involve? [1]

A

ONLY the transfer of negative charge (electrons)

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18
Q

What is an electric field? [2]

A

the region in which an electric charge experiences a force

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19
Q

How much is 1 micro coulomb in coulombs? [1]

A

10⁻⁶ C = one millionth of a coulomb

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20
Q

What are the two types of electricity? [2]

A
  • Static
  • Current
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21
Q

What is current? [2]

A
  • when charges are moving
  • when you can get the electrons to drift
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22
Q

What is an Electric Current? [1]

A

The rate of flow of charge

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23
Q

What is formula relating current and charge? [2]

A

Current = Charge / Time

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24
Q

What is the symbol formula for current? [1]

A

I = Q / T

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25
Q

What is the unit for current? [1]

A

Amperes

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26
Q

What is A.C.? [2]

A
  • when the current swings back and forth in every halfcycle
27
Q

What is D.C? [1]

A
  • current only flows in one direction
28
Q

What is electrical conduction in metals? [1]

A
  • the movement of delocalised electrons
29
Q

Where is conventional current from? [1]

A

POSITIVE TO NEGATIVE

30
Q

Where is the flow of electrons from? [1]

A

NEGATIVE TO POSITIVE

31
Q

What is the use of an ammeter? [2]

A
  • measures current
  • how much charge flows per second through the wire
32
Q

What is the use of a voltmeter? [1]

A

tool used to measure voltage

33
Q

What is Electromotive Force (E.M.F)? [3]

A

the electrical work done by a source in moving a unit charge around a complete circuit

34
Q

What is E.M.F measured in? [1]

A

Volts

35
Q

What is Potential Difference (P.D.)? [2]

A

the work done by a unit charge passing between two points in a circuit

36
Q

What is P.D. measured in? [1]

A

Volts

37
Q

What is the formula for resistance? [2]

A

Resistance = Voltage / Current

38
Q

What is the symbol formula for Resistance? [1]

A

R = V / I

39
Q

What is resistance? [2]

A

ratio of voltage to current in an appliance

40
Q

What is the unit for Resistance? [1]

A

Ohms

41
Q

Where is a Voltmeter meant to be connected? [1]

A

across the appliance

42
Q

What’s the formula for E.M.F? [2]

A

volts = joules / coulomb

43
Q

What’s the symbol formula for E.M.F? [1]

A

V = J / C

44
Q

What’s is Ohm’s Law? [1]

A

voltage / current

45
Q

What is Ohm’s Law in symbols? [1]

A

V / I

46
Q

Why is copper used for wiring? [2]

A
  • good electrical conductor
  • cheap
47
Q

What are some factors which affect resistance? [3]

A
  • length
  • cross-sectional area
  • temperature
48
Q

What is the relationship between length and resistance? [2]

A

R ∝ L

49
Q

What does the relationship between length and resistance mean? [2]

A
  • if length increases, resistance increases too
50
Q

What is the relationship between temperature and resistance? [2]

A
  • the greater the temperature, the greater the resistance
51
Q

What is the relationship between the cross-sectional area of a wire and resistance? [2]

A
  • the smaller the cross-sectional area of a wire, the greater the resistance
52
Q

What are Ohmic conductors and how do their graphs look? [2]

A
  • conductors which obey Ohm’s Law
  • their I-V graph is a straight line through the origin
53
Q

What are Non-Ohmic conductors and how do their graphs look? [2]

A
  • conductors that do not obey Ohm’s Law
  • their I-V graph is not a straight line and doesn’t go through the origin
54
Q

What is the formula for energy? [2]

A

Energy = Voltage x Current x Time

55
Q

What is the symbol formula for energy? [1]

A

E = VIT

56
Q

What is the formula for power? [2]

A

Power = Voltage x Current

57
Q

What is the symbol formula for power? [1]

A

P = VI

58
Q

How do you work out the total resistance in a series circuit? [1]

A

Rₜ = R₁ + R₂ + R₃

59
Q

How do you work out the E.M.F of the source in a series circuit? [2]

A
  • sum of PD across each
  • E.M.F. = V₁ + V₂ + V₃
60
Q

What happens to the current if there’s a bigger resistance in a parallel circuit? [1]

A
  • current decreases
61
Q

What happens to the current in a parallel circuit when it reaches a branch point? [1]

A

the current splits ups

62
Q

How do you work out the total resistance in a parallel circuit? [2]

A

1/Rₜ = 1/R₁ + 1/R₂ + …

63
Q

How much voltage does each branch get in a parallel circuit? [1]

A

same voltage as the supply

64
Q

How do I find out the total voltage in a parallel circuit? [2]

A

Vₜ = V₁ = V₂

65
Q

What is the formula for power dissipated in a resistor? [2]

A

power = current² x resistance

66
Q

What is the symbol formula for power dissipated in a resistor? [2]

A

P = I²R

Physics (15 decks)

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