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Physical Science > Electrical Cells And Circuits > Flashcards

Electrical Cells And Circuits Flashcards

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1
Q

What is a cell

A

It is a source of electrical energy and generates electricity by using chemical reactions

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2
Q

What does an electrical cell consist of

A

An electrical cell consists of two solid electrodes and electrolytes

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3
Q

What is an electrolyte

A

Solution that can conduct electricity

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4
Q

What does an electrolyte consist of

A

Thousands of positive and negative ions

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5
Q

What happens when two electrodes are connected in a circuit

A

A chemical reaction takes place in the cell which causes the flow of electrical charge (electrons) through an external circuit

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6
Q

What energy conversion takes place in a cell

A

There is chemical potential energy in the cell —> chemical energy —> electrical energy —> Kinect if energy

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7
Q

What is potential difference

A

The work done per unit positive charge

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8
Q

What is voltage measured in

A

Volts (V)

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9
Q

What type of cells are used in our toys, phones and torches etc

A

Dry cells

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10
Q

What type of battery does a car battery use

A

A wet cell

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11
Q

What is a battery

A

When two or more cells are connected in series

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12
Q

What are the two ways a cells can be connected in a battery

A

Series and in parallel

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13
Q

What happens to the voltage when cells are connected in series

A

The voltage is added and produces more energy to the charges that move through the circuit

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14
Q

What happens to the voltage when cells are connected in parallel

A

The voltage is the same as one cell

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15
Q

What are the two ways to make an electric cell yourself

A

Firstly By means of using a lemon, a coin and a nail. When you take a lemon put a coin on one side and a nail on the other. When you connect conduction wire (coin is the positive electrode and the coin is the positive electrode) and an LED light it will light up.

Secondly by means of a copper sulphate solution, copper plate and zinc sulphate solution and zinc plate. When you take a copper plate and put it into a beaker full of copper sulphate solution and take a zinc plate and put it into a beaker full of zinc sulphate solution then you use a paper towel and soak it in either solutions then put one side in one beaker and the other side in the other. When you connect conduction wire (positive terminal on copper plate, negative terminal on the zinc plate) and an LED light it will light up

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16
Q

What is the positive electrode called

A

The anode

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17
Q

What is the negative electrode

A

The cathode

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18
Q

When is a cell flat

A

When the chemical energy un the cell is depleted and all the chemicals in the cell are used up

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19
Q

What pair of metals makes a cell with the greatest voltage

A

Copper and magnesium

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20
Q

What happens if the same metal are used to create a cells electrodes

A

The voltage will result in 0

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21
Q

What is an insulator

A

Materials that do not allow electrical charges to flow through them

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22
Q

What is an electric current

A

The rate of flow of an electric charge

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23
Q

What is a conductor

A

A material which allows charges to flow through it. They are mostly metals

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24
Q

What Is electrical resistance

A

The resistance offer d by a conductor against the flow of current

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25
Q

What is a good conductor

A

A conductor with a low resistance and allows a strong current through.

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26
Q

What is a resistor

A

An electrical component that goes against the flow of current

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27
Q

What does a resistor consist of

A

Conductive material with a high resistance

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28
Q

Why do we use resistors in circuits

A

To control the current or for the provisions of useful energy transfer

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29
Q

What are ways resistance is used for electrical appliances

A

Nichrome is used for heating elements in electrical appliances because it has a very high resistance eg stoves

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30
Q

How does a lightbulb light up

A

The filament of a lightbulb is made of very thin tungsten wire which produces a bright light when the wire becomes very hot.

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31
Q

What are the factors that influence the resistance of a conductor

A

Type of material, length of the conductor, thickness of the conductor and temperature of the conductor

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32
Q

How does the type of material Influence the resistance of a conductor

A

Different conductors have different levels of resistance against electrical current. Eg copper wire conducts a greater current than an equal length of Nichrome wire with the thickness and temperature.

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33
Q

How does the length of a conductor influence the resistance of the conductor

A

The longer the wire this more resistance and the less the current, the shorter the wire the less the resistance and the more the current

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34
Q

How does the thickness of the conductor influence the resistance

A

The thinker the wire the less the resistance and the more the current. The thinner the resistance the more the resistance and the less the current

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35
Q

How does the temperature of the conductor influence the resistance of the conductor

A

Hotter conductors offer more resistance and less current than colder resistors which offer less resistance and more current

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36
Q

What does current consist of

A

Negatively charged particles that are called electrons

37
Q

What are the two types of current

A

Conventional current and electron current

38
Q

What is conventional current

A

An electrical current where the charges flow from the positive pole to the negative pile of the cell or battery

39
Q

What is an electron current

A

A current where the charges flow from negative to positive

40
Q

Which current do we use when working with electrical circuits and why

A

We use conventional current to keep with the internal decision

41
Q

How is an ammeter connected in the circuit

A

In series

42
Q

What is used to measure electrical current

A

An ammeter

43
Q

How much resistance does an ammeter have

A

An ammeter has little to no resistance therefore it measures the current accurately

44
Q

How do we connect the wires of an ammeter into the circuit

A

The black (negative contact socket) should lead to the negative pole of the battery. The red (positive contact socket) should lead to positive pole of the cell or battery.

45
Q

What May damage an ammeter

A

When it is connected the wrong way around, or connected in such a way that the needle moves to the end of the scale

46
Q

When charges lose energy in what form do they transfer the energy to the resistor

A

In the form of heat, light or sound energy

47
Q

What measures voltage

A

A voltmeter

48
Q

How is a voltmeter connected in a circuit

A

It’s connected in parallel

49
Q

How much resistance does a voltmeter offer

A

A great resistance

50
Q

How must the wires of a voltmeter be connected in a circuit

A

The same as an ammeter. The black (negative ) contact socket leads to the negative pole of the cell or battery. The red (positive) contact socket leads to the positive pole of the cell or battery

51
Q

What does resistance control

A

The current and voltage in the circuit

52
Q

What is a rheostat

A

A resistors who’s resistance is adjustable

53
Q

How does a rheostat work

A

It has an ordinary resistor with a fixed resistance. Then it has a sliding contact which changes the length of the resistance wire through which current flows and therefore also it’s resistance

54
Q

When are cells connected in series

A

One after another an positive to negative

55
Q

When are cells connected in parallel

A

Positive pole to positive pole and negative pole to negative pole

56
Q

How do we calculate the total voltage of cells in series

A

We add the voltages of the individual cells

57
Q

How do we calculate the voltage of cells connected in parallel

A

When cells are connected in parallel the voltage over them will be the same as for only one cell

58
Q

What is the difference between cells in series and cells in parallel

A

Cells in series deliver a stronger current because all the cells work at once but it doesn’t last as long as cells connected in parallel because the cells in parallel are used one at a time.

59
Q

What happens to the current in a series circuit

A

It is the same throughout the circuit

60
Q

What happens to the current in a parallel circuit

A

The current is divided and the sum of the currents going through the resistors is the same as the main current going through the battery

61
Q

What happens to the voltage in a series circuit

A

The voltage of the resistors added together should equal the total voltage over the battery or cell

62
Q

What happens to the voltage in a parallel circuit

A

The voltage is the same

63
Q

What happens to resistors connected in series

A

The resistor with the highest resistance will have the highest voltmeter reading and the resistor with the lowest resistance will have the lowest voltmeter reading. When resistors are added in series the the total current is decreases.

64
Q

What happens to resistance in parallel circuits

A

When resistors are added in parallel the total resistance decreases and the total current is increased. Parallel resistors are referred to ad current distributors

65
Q

What is the difference between a parallel and a series circuit

A
  • In a series circuit the components are connected one after another while In a parallel circuit they are connected in parallel to one another
    -if a light break breaks or fuses in a series circuit the rest of the lightbulbs won’t work whereas if a light bulb breaks or fuses in a parallel circuit the rest will still work.
    -when lightbulbs are connected in series the fainter the lightbulbs will shine when more are added, whereas when lightbulbs are added in parallel the lightbulbs will stay at the same brightness even if more lightbulbs are added.
66
Q

What is ohms law

A

The current through a conductor is directly proportional to the potential difference across the conductor at a constant temperature

67
Q

What is the relationship between current and voltage

A

Current is directly proportional to voltage

68
Q

What is the relationship between voltage and resistance

A

Voltage is directly proportional to resistance

69
Q

What is the relationship between current and resistance

A

Current is inversely proportional to resistance

69
Q

How is the lighting in our house connected

A

In parallel

70
Q

What is the electrical power supply in our houses

A

220V and 60A

71
Q

What are safety devices used in a circuit

A

Fuses, circuit breakers and earth leakage breakers

72
Q

What is a fuse

A

A safety device used to protect a circuit against the heating effect of an electric current. It consists of a very thin piece of wire with a low melting point which is connected in series in a circuit so that all the available current May flow through it.

73
Q

How does a fuse work

A

When the current gets to strong it heats up the wire and it melts. This breaks the circuit and current stops flowing

74
Q

What does an electricity distribution board look like

A

It consists of a big red main switch, a big black Earth leakage circuit breaker and a bunch of smaller circuit breaks

75
Q

What are circuit breakers

A

Electric switches (electromagnetic) that are connected to a room or appliance that automatically switches off the flow of current when an overload or short circuit occurs

76
Q

What is an earth leakage circuit breaker

A

A safety device that is able to switch off the electricity supply to all circuits when a current of 30mA or more leaks to the ground

77
Q

How does an earth leakage circuit breaker work

A

It continuously tests the flow of electrical current through a circuit. When the amount of current that is drawn through the charged wires in a circuit differs from the quantity that returns through the neutral wire the breaker cuts the power.

78
Q

How is electricity brought to the main switch

A

From the power station the electricity is brought to the meter box by means of Overhead wiring or underground cables

79
Q

Where does electricity flow to from the meter box

A

To the distribution board

80
Q

What is the main switch

A

Used to switch electricity supply to the house on and off

81
Q

Where is electricity generated

A

In a power station

82
Q

What is a power station

A

A system for the generation of electricity

83
Q

What is the genera method for the generation of electricity at a power station

A

To rotate a tubune that in turn rotates a generator

84
Q

How energy that we use in SA comes from coal

A

Approximately 3 quarters

85
Q

Where are most fo the power stations in South Africa

A

In mpumalanga because there is a rich supply of coal there

86
Q

What are the steps of how a coal driven power station generates electricity

A
  1. Coal in a furnace heats water
  2. Steam is generated from the water
  3. The steam turns a turbine
  4. Which in turn turns the generator which converts the kinetic energy to electrical energy
  5. The energy is changed to correct the voltage in a transformer
  6. The electricity is distributed by means of pylons and high tension cables into the national network to houses schools, factories etc
87
Q

What are the disadvantages of a coal power station

A

Air pollution, which In turn causes acid rain, and contributes to global warming and non renewable resources are being exhausted

Physical Science (29 decks)

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