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Abi Science 2017 > Electric Circuits > Flashcards

Electric Circuits Flashcards

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1
Q

What is the function of a battery?

A

To provide power to a circuit

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2
Q

What is a cell?

A

An energy source for a circuit

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3
Q

What is a battery?

A

Multiple cells

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4
Q

What is the function of a connecting wire?

A

To allow electrons to flow

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5
Q

What is the function of a switch?

A

To “pause” and “restart” the flow of charge

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6
Q

What is the function of a resistor?

A

To oppose the flow of charge

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7
Q

What is the function of a rheostat?

A

To allow the resistance to be adjusted

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8
Q

What is another name for a rheostat?

A

Potentiometer

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9
Q

What is the function of a lightbulb?

A

To show current in the form of light

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10
Q

What is the function of a LED?

A

To allow current to flow in one direction

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11
Q

What is the function of an ammeter?

A

To measure current

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12
Q

What is the function of a voltmeter?

A

To measure the potential difference in current

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13
Q

What is the difference between emf and potential difference?

A

Emf is voltage when current is not flowing

Potential difference is voltage when current if flowing

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14
Q

How are pd and emf measured?

A

In Volts

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15
Q

How should a voltmeter be connected in a circuit?

A

In parallel

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16
Q

Why does a voltmeter need to be connected in parallel?

A

It has a high resistance
If it were connected in series, it would serve as another resistor
This would affect the reading

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17
Q

What is current?

A

The number of coulombs of charge that flow past a point in the circuit every second

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18
Q

What are the two requirements for charges to be able to flow in a circuit?

A

There must be no breaks in the circuit

The charges must have energy to be able to move

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19
Q

What is the definition of current?

A

The rate of flow of charge

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20
Q

What is the symbol for current?

A

I

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21
Q

What is the measurement of current?

A

Ampere

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22
Q

What is one ampere?

A

One coulomb that flows past a certain point in one second

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23
Q

What is the equation for current?

A

Current is equal to charge over time
Q
I = —
Δt

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24
Q

What is the conventional flow of current?

A

From the positive terminal of a battery to the negative terminal of a battery

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25
Q

How is the direction of current shown?

A

Using arrowheads

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26
Q

What instrument is used to measure current?

A

An ammeter

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27
Q

How is an ammeter connected to a circuit?

A

In series

28
Q

Why can an ammeter be connected in series?

A

It has a very low resistance

It does not decrease the current in a circuit

29
Q

What is the definition of resistance?

A

The property of a material which causes it to oppose the flow of charge through it

30
Q

When can resistance be a detriment?

A

When current does not need to be opposed

31
Q

Give an example of when resistance is detrimental

A

High voltage transmission lines
If there is too much resistance, they heat up
This causes energy to be lost to the environment

32
Q

When can resistance be useful?

A

When the heat or light energy that resistors cause to be released is needed

33
Q

Give two examples of where resistance is useful

A

Heating elements

In electronics

34
Q

How can resistance be useful in electronics?

A

It restricts the flow of current to other components, thereby protecting them

35
Q

How do reinstalls cause things to heat up?

A

Electrons bump into the particles of the resistor
Kinetic energy is transferred
Raises the temperature of the resistor

36
Q

What is the formula for resistance?

A

Resistance is equal to voltage over current
V
R = —
I

37
Q

What is the relationship between resistance and voltage?

A

Directly proportional

As the one increases, so does the other

38
Q

What is the relationship between resistance and current?

A

Inversely proportional

As the one increases, the other decreases

39
Q

What is the unit of measurement for resistance?

A

The ohm

40
Q

What is the symbol for an ohm?

A

Ω

41
Q

What is an ohm?

A

One volt per ampere

42
Q

What four factors affect resistance?

A

Length
Thickness or cross-sectional area
Temperature
Type of material

43
Q

How does length affect resistance?

A

The greater the length of a resistor, the more resistance it has

44
Q

How does thickness or cross-sectional area affect resistance?

A

The greater the cross-sectional area of a resistor, the smaller its resistance

45
Q

How does temperature affect resistance?

A

The higher the temperature of a resistor, the greater its resistance

46
Q

How does the type of material affect resistance?

A

The greater the resistivity of a metal, the greater its resistance

47
Q

What does “resistors connected in series” mean?

A

There is only one path along which the current can flow

48
Q

What does mean to have “resistors connected in parallel”?

A

There is more than one path along which current can flow

49
Q

How is current affected when resistors are connected in series?

A

The more resistors there are, the slower the current flows. However, current is equal across all of the resistors

50
Q

What is the formula for finding the equivalent resistance of resistors connected in series?

A

Rtotal = r1 + r2 …

51
Q

How is voltage affected by resistors connected in series?

A

It is divided

The amount of voltage in one resistor is proportional to the a,punt of resistance it offers

52
Q

What results in a potential difference across a resistor?

A

Energy is transferred as it passes through the resistor

The decrease in potential electrical energy results in a potential difference across the resistor

53
Q

What is equivalent resistance in a parallel circuit like?

A

It is smaller than the resistance of lowest resistor in the set

54
Q

How is equivalent resistance in a parallel circuit calculated?

A

1 1 1 1
– = – + – + – …
Rp r1 r2 r3

55
Q

How is current affected when resistors are connected in parallel?

A

It is divided

The sum of the current in the branches is equal to the total current in the circuit

56
Q

How is potential difference affected by resistors in parallel?

A

It is equal to the potential resistance across the whole combination

57
Q

How do cells work?

A

They convert chemical potential energy into electrical energy

58
Q

What are the three common components in a cell?

A

Positive electrode
Electrolyte
Negative electrode

59
Q

What form is the electrolyte in a cell?

A

It can be a liquid, paste or a powder

60
Q

What is the electrolyte in an alkaline cell?

A

Potassium hydroxide

61
Q

What does the negative terminal of an alkaline cell consist of?

A

Zinc powder

62
Q

What does the positive terminal of an alkaline cell consist of?

A

Manganese dioxide

63
Q

What happens when this alkaline cell is in use?

A

The manganese dioxide is converted into manganese oxide and hydroxide ions
These ions react with the zinc metal
This forms zinc oxide, water and electrons

64
Q

What constitutes an electric current?

A

Moving charges

65
Q

When is a cell said to be flat?

A

When too few electrons are being generated

66
Q

What causes a cell to go flat?

A

The manganese oxide has been almost used up

Abi Science 2017 (18 decks)

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