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year 2 chap 13 Flashcards

1
Q

what are electrical systems?

A

an object made up of various electrical components that allow for transporting electrical energy

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2
Q

when people invent or construct electrical appliances, what do they use to represent their designs?

A

diagrams

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3
Q

what do the diagrams include?

A

the symbols that represent different components of an electrical system

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4
Q

what is a cell in an electrical system?

A

an energy source

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5
Q

shorter line in the circuit symbol for the cell is the ___ of the cell and the longer line is the ___ of the cell

A

negative side ; positive side

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6
Q

what type of circuit is it if the switch is open and the bulb does not light up?

A

an open circuit

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7
Q

what type of circuit is if the switch is closed the bulb lights up?

A

a closed circuit

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8
Q

current can only flow in ___ direction

A

one

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9
Q

current flows from ‘positive to negative’ or ‘negative to positive’

A

positive to negative

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10
Q

what are the main components of an electrical system?

A
  • cell
  • electric charge
  • wires
  • electrical device (e.g bulb)
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11
Q

how many paths for electrical current are there in a series circuit?

A

1

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12
Q

how many paths for electrical current are there in a parallel circuit?

A

more than 1

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13
Q

are the brightness of the bulbs in a series circuit brighter or dimmer when there is only one battery for two bulbs to share?

A

dimmer

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14
Q

are the brightness of the bulbs in a parallel circuit brighter or dimmer when there is only one battery for two bulbs to share?

A

brighter

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15
Q

is the brightness of a bulb connected in series in a parallel circuit brighter or dimmer than the other bulbs connected in parallel?

A

brighter

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16
Q

the rate at which electric charge flows is known as the __

A

electric current, I

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17
Q

what is the SI unit for electric charge?

A

ampere (A)

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18
Q

how can we measure the current flowing in an electric circuit?

A

using an ammeter

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19
Q

measurement of an electric current indicates ___

A

how much electric charge is flowing past a particular point in an electric circuit per unit time

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20
Q

in an electric circuit, why is there the flow of electric charge?

A

because of the movement of electrons in the electrical conductors

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21
Q

the greater the flow of electric charge per unit time, ‘the larger the current’ or ‘the smaller the current’

A

the larger the current

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22
Q

to measure the current flowing through a circuit, an ammeter is connected in ‘series’ or ‘parallel’ within a circuit

A

series

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23
Q

what is potential difference?

A

the amount of energy needed to move a unit charge from one point in an electric circuit to another point

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24
Q

what can the amount of energy needed to move a unit charge from one point in an electric circuit to another point also be referred to as?

A

voltage

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25
what does a voltmeter do?
it measures the potential difference between two points in an electric circuit
26
what is the SI unit of potential difference?
volt (V)
27
to measure the potential difference across an electrical component such as a bulb, a voltmeter is connected 'in series' or 'in parallel' to the electrical component?
in parallel
28
what is electrical resistance?
a measure of how much the component opposes the flow of electric current
29
conductors of electricity have __ resistance to current
low
30
insulators of electricity have __ resistance to current
high
31
what are examples of conductors of electricity?
copper and silver
32
what are examples of insulators of electricity?
plastic and glass
33
what happens when electric current flows through some conductors that have higher resistance than copper and silver?
much electrical energy is converted to other forms like heat and light energy, which can be used for different purposes
34
what are examples of conductors that have higher resistance than copper and silver?
tungsten and nichrome
35
how are these conductors that have higher resistance than copper and silver used?
tungsten is used to make lightbulbs
36
what is the SI unit of electrical resistance?
ohm (Ω)
37
what are resistors?
electrical components that reduce the flow of current in a circuit
38
what happens when a resistor is added to an electrical circuit?
it is more difficult for electric charge to flow in the circuit
39
what happens to the current and the bulb when it is more difficult for electric charge to flow in the circuit?
the current flowing through the bulb decreases and the bulb becomes less bright
40
what are the 2 types of resistors?
fixed resistor and variable resistor
41
what type of resistance does a fixed resistor have?
fixed, non-adjustable electrical resistance
42
what type of resistance does a variable resistor have?
a range of electrical resistance that can be adjusted
43
what are fixed resistors made up of?
fixed resistors are made of a combination of materials
44
conductors of electricity would have 'more resistance' or 'less resistance' to electric currents than insulators?
more resistance
45
what is the resistive element made up of?
a mixture of fine carbon particles and a non-conductive ceramic material
46
the more carbon, the ___ resistance
less
47
why are resistors used in circuits?
resistors are used to keep the current in circuits to a safe level and prevent overheating of the circuits
48
variable resistors are used in household appliances to?
control the current in a circuit
49
what is an example of variable resistors used in household appliances?
variable resistors are used in dimmers that control the brightness of light in a room
50
what type of resistor is a rheostat?
a variable resistor
51
the rheostat has a ___ that can be shifted to ___ and change the amount of current in the circuit
slider ; adjust the resistance
52
what do you call 2 cells that are placed together in an electric circuit?
a battery of two cells
53
why are two bulbs connected in parallel usually brighter than two bulbs connected in series?
because in series, the voltage is shared by two bulbs but in parallel, the voltage experienced by both bulbs is the same
54
what are the 3 useful effects of a current flowing in an electrical system?
chemical effect, heating effect and magnetic effect
55
what is the chemical effect of an electric current?
a chemical change takes place when an electric current passes through certain chemical solutions or liquids
56
how can the chemical effect of an electric current be useful?
this effect can be used for extracting metals or electroplating an object w. a thin layer of metal
57
what is the heating effect of an electric current?
when an electric current is passed through a heating element, some electrical energy may be converted to heat energy
58
what does a heating element consist of?
it consists of a wire made of a high-resistance material like nichrome
59
a high-resistance material can withstand ___
high temperatures
60
how can the heating effect of an electric current be useful?
some household appliances use a heating element to work, these include the hairdryer, rice cooker, toaster and kettle
61
what is the magnetic effect of an electric current?
an electric current has an effect on magnets
62
what happens when an electric current flows through a wire placed near a compass?
the needle in the compass is deflected
63
how are electromagnets created?
by passing an electric current through a coil of wire, to turn it into a temporary magnet
64
how are electromagnets used?
electromagnets can be found in robot systems assist surgeons as the force applied by a surgeon’s hand may be too great for the human body
65
what causes electrical fires?
when an electrical circuit is damaged/overloaded, a very large amt of current may be drawn from the power supply which can result in excessive heat & cause wires to melt can even cause a fire
66
what are the 2 harmful effects of electricity?
electrical fire and electric shock
67
what is overloading?
when multiple plugs are inserted in the same socket
68
what are wires carrying electricity to electrical appliances insulated with?
plastic/rubber
69
why are wires carrying electricity to electrical appliances insulated with plastic/rubber?
to protect the user from an electric shock
70
how do electric shocks happen?
when the insulating material is worn out, the conducting wires are exposed the user accidentally touches the exposed wires
71
what are the 2 safety devices in our household electrical systems?
fuse and circuit breaker
72
every electrical appliance has a limit to the ___ so that it can operate safely
max amount of current that flows through it
73
what is a fuse?
an electrical component used to protect the electrical appliance from excess current
74
what does the current rating of a fuse indicate?
it indicates the maximum amount of current that can flow through the fuse before the wire inside it melts
75
what causes the thin wire inside the fuse to melt?
the current flowing through the appliance is larger than the current rating of its fuse due to an electric fault
76
what happens when the thin wire inside the fuse melts?
the circuit becomes an open circuit & no current is able to flow through the appliance
77
after the fault in the appliance is fixed, ___ before the appliance can be used again
the damaged fuse needs to be replaced
78
what is the full name of the circuit breaker?
the Residual Current Circuit Breaker (RCCB)
79
the circuit breaker has ___ and the switches are connected to different parts of a household
many individual switches
80
what causes the switch linked to the appliance in the circuit breaker to trip and cut off the current?
when the current flow is too large due to a faulty electrical appliance
81
what can the tripping of the switch in the circuit breaker prevent?
it can prevent electric shocks
82
the RCCB can be reactivated ___ after the faulty appliance is repaired
manually
83
how can we reduce the consumption of electrical energy in our daily lives?
by making choices that are energy-efficient
84
what does being energy efficient mean?
it means to use less electrical energy to perform the same tasks
85
consumption of electrical energy depends on?
the rate at which electrical energy is used by an electrical appliance to serve it’s function
86
what is the amount of electrical energy used for conversion to other forms of energy per unit time referred to?
the power of an electrical appliance
87
what is the SI unit of power?
watt (W)
88
what is the monthly electrical energy consumption in our electricity bills measured in?
it is measured in kilowatt-hours (kWh)
89
1 kW = ___ W
1000 W
90
how to calculate kilowatt-hours?
electrical energy (kWh) = power (kW) x time (h)
91
how much energy is needed to keep a 1000 watt (1 kW) appliance running for one hour
1 kWh
92
1 kWh of electrical energy consumption is equal to ___ of energy
3 600 000 J
93
how to convert watts into kilowatts?
the number of watts divided by a thousand
94
how to calculate how much energy is being consumed in 1 kWh?
1 kW x 1h = 1000 W x 3600 seconds = 3 600 000 J
95
how much is 80 W in kilowatts?
0.080 kW
96
how to calculate the cost of electrical energy consumption of an electrical appliance?
we need to know the current electricity tariff in the location
97
electricity tariff is expressed in?
cents per kilowatt-hour
98
if an electric fan has a power rating of 60 W and the electricity tariff is 27 cents per kWh what is the cost of electrical energy consumption of an electric fan if it is switched on for 8 hours?
power (kW) x time (h) = (60 ÷ 1000) x 8h = 0.060 kW x 8h = 0.48 kWh 0.48 kWh x $0.27 = $0.1296
99
name a way to conserve energy in households
buy electrical appliances that have energy labels with 3 or more ticks

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