Electricity (Seneca) Flashcards
1
Q
Components are shown using …
A
symbols
2
Q
Straight lines show wires joining the …
A
components
3
Q
The wires don’t pass through the …
A
components
4
Q
An electric current is the …
A
flow (movement) of electric charges.
5
Q
Electric current is measured in …
A
amperes (A).
6
Q
The flow of charge (C) =
A
current (A) x time (s).
7
Q
The flow of charge (1.) = current (2) x time (3.).
A
- C
- A
- s
8
Q
A current has the ———— at every point in a single closed loop.
A
same value
9
Q
A current has the same value at …
A
every point in a single closed loop.
10
Q
What is needed for a current to flow?
A
- closed circuit
- source of potential difference
- electrons
11
Q
What are Amperes (A) the unit for?
A
Electrical current
12
Q
The current is equal to the …
A
charge divided by the time.
13
Q
I =
A
Q/t
14
Q
The movement of electric charges is the basis of …
A
electrical current
15
Q
An electrical conductor is a …
A
material that allows electric currents (flow of electric charges) to pass through it.
16
Q
All ——- are electrical conductors.
A
metals
17
Q
An electrical insulator is a …
A
material that doesn’t allow electric currents (flow of electric charges) to pass through it.
18
Q
—————— are electrical insulators.
A
Plastic and glass
19
Q
An electrical conductor has lots of …
A
charges that are free to move.
20
Q
In a metal, the charges that are …
A
free to move are electrons.
21
Q
The electric current through the metal is the flow of …
A
these free electrons.
22
Q
An electrical insulator has …
A
no free electrons.
23
Q
An electrical insulator has no free electrons. No charges are …
A
free to move and carry a current.
24
Q
Which charges are free to move in metals?
A
Electrons
25
Give examples of electrical insulators.
- wood
- plastic
- rubber
26
Potential difference (p.d.) is measured in ----- and is also called voltage.
volts (V)
27
Potential difference (p.d.) is measured in volts (V) and is also called ...
voltage
28
The energy is transferred to the electrical components in a circuit when ...
the charge carriers pass through them.
29
We use a ------- to measure potential difference (or voltage).
voltmeter
30
We use a voltmeter to measure ...
potential difference (or voltage).
31
Potential difference is the ...
difference in the amount of energy that charge carriers have between two points in a circuit.
32
potential difference(V) =
current (A) ×resistance (Ω)
33
A potential difference of one Volt is equal to ...
one Joule of energy being used by one Coulomb of charge when it flows between two points in a circuit.
34
voltage (V) ×charge (C) =
energy(J)
35
An ammeter measures the ...
flow of current that passes through it.
36
Ammeters have to be connected in ...
series (in the same loop of the circuit) with the electrical component whose current you are measuring.
37
Voltmeters measure the...
potential difference (voltage) between two points in a circuit.
38
Voltmeters must always be connected in ...
parallel (on a separate branch of the circuit) with the two points being measured.
39
The current is a 1. . Current is measured through 2. .
1. flow of charge
2. a component
40
Potential difference is the energy used between two points in a circuit, therefore it is measured ...
between two points either side of a component.
41
Potential difference is the energy used between two points in a circuit, therefore it is measured between two points either side of a component.
We describe this as ...
the potential difference measured across a component.
42
When charge flows in an electric circuit, the size of the current is affected by two things:
1. The resistance: If the resistance is increased, the current will decrease.
2. The potential difference: If the potential difference is increased the current will increase.
43
Resistance is measured in ...
ohms, Ω.
44
Resistance is a measure of the...
difficulty of the flow of current through a component
45
An electric current will increase when the number of ohms ...
decreases
46
An electric current will increase when potential different...
increases
47
An electric current will increase when resistance...
decreases
48
resistance (Ω) =
voltage (V) / Current (A)
49
We calculate potential difference using a voltmeter and current using an ammeter at the ...
same time
50
The longer the wire, the ------------- the resistance.
higher
51
We can plot a current-voltage graph by ...
varying the potential difference across a circuit component.
52
what is Ohm’s Law?
current = potential difference/resistance.
53
In Current-Voltage Graph for a Resistor, the slope of the graph is equal to ...
1/resistance.
54
In Current-Voltage Graph for a Resistor, the constant slope (straight line graph) tells us that the resistance is ...
constant.
55
In Current-Voltage Graph for a Resistor, what effect will increasing the current through a filament bulb have on the graph?
It will curve because the temperature and resistance is rising.
56
In Current-Voltage Graph for a Filament Lamp, The gradient (slope) ----------- at larger potential differences.
decreases
57
In Current-Voltage Graph for a Filament Lamp, when the current through a filament (thin wire) lamp increases, the temperature of the lamp ...
increases.
58
In Current-Voltage Graph for a Filament Lamp, when the current through a filament (thin wire) lamp increases, the temperature of the lamp increases.
This increases ...
the resistance of the lamp and causes the graph to curve.
59
We can plot a current-voltage graph by changing the potential difference across a circuit component and measuring the current. A constant slope tells us that the resistance is ...
constant.
60
A diode is a ...
component that only allows current to flow through it in one direction.
61
A rectifier is a ...
component that turns an alternating current (repeatedly changes direction) into a direct current (one direction)
62
Diodes act as rectifiers as they ...
block the alternating current when it changes direction.
63
A thermistor is a ...
component where resistance changes with its temperature.
64
A thermistor is a component where resistance changes with its temperature.
Usually, increasing temperature --------- the resistance.
decreases
65
We can use a thermistor to ...
turn a heater off when a house reaches certain temperatures.
66
A light dependent resistor (LDR)s resistance changes with ...
light intensity
67
A light dependent resistor (LDR)s resistance changes with light intensity.
Usually, increasing light intensity ------------ the resistance.
decreases
68
We can use LDRs to ...
switch lights on when it gets dark or to know whether or not a camera phone needs to use “flash”.
69
A diode is a component through which current can flow in only one direction. Because of this, diodes act as ...
rectifiers.
70
The diode blocks the ...
alternating current when it changes direction.
71
The flow of current transfers ...
energy from the energy source to the components.
72
The components then transfer energy to ...
their surroundings.
73
The power of a component is equal to ...
the current through the component multiplied by the potential difference across the component.
74
Power (W) =
Current (A) x Voltage (V)
75
Current (A) x Voltage (V)=
Power (W)
76
Power (W) =
Current (squared) (A) x resistance (Ω)
77
Current (squared) (A) x resistance (Ω)=
Power (W)
78
The total energy transferred to a component is equal to ...
the power multiplied by the time a current flows for.
79
Energy (j) =
Power (W) x time (s)
80
Power (W) =
voltage (V) (squared)/ resistance (Ω)
81
The power of a component is equal to ...
the current through the component multiplied by the potential difference across the component.
82
The total energy transferred to a component is equal to ...
the power multiplied by the time that the current was flowing for.
83
The current through an ohmic conductor (at a constant temperature) is ...
directly proportional to the potential difference across the resistor.
84
The current through an ohmic conductor (at a -------------------------) is directly proportional to the potential difference across the resistor.
constant temperature
85
The current through an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the resistor.
This means that the resistance ...
remains constant as the current changes.
86
What remains constant for an ohmic conductor?
resistance
87
What is the law of Ohm’s Law?
The current through an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the resistor.
88
Resistance (Ω) =
potential difference (V) /current (A)
89
An Ohmic conductor is a conductor that ...
obeys Ohm’s Law.
90
In a series circuit, the current is ----------------- in the circuit.
the same at all points
91
A battery is made by ...
joining cells together.
92
What are the key features of a series circuit?
- All components are attached in a row.
- The current is equal everywhere in the circuit.
- The voltage across each component is different.
- The sum of the voltages across each component is the total battery voltage.
93
In a parallel circuit, components are connected on separate branches of wires to the energy source. The current through the battery is ------- than the current through each of the individual branches.
larger
94
In the lighting circuit of your house, each lamp is connected to the energy supply in parallel. This arrangement has two main advantages:
- Each lamp may be switched on and off separately
- If one lamp breaks, current still flows through the others
95
The combined resistance of two resistors in parallel is ------than the resistances of either of the two resistors by themselves.
less
96
A parallel circuit has …
components connected on separate branches of wires to the energy source. The current is split between these branches.
97
A series circuit has …
all its components connected on the same line as each other. The charge flows through the circuit like water flows through pipes. The current is the same at all points of the circuit.
98
Consider a circuit with two resistors of equal value connected in series. If another resistor of the same value is connected in parallel with ONE of these resistors, what will be the effect on the total resistance of the circuit?
The resistance decreases.
99
Two ohmic conductors are connected in series, with the second conductor having a larger drop in potential difference across it. What can be determined about the values of the resistances of the conductors?
The second conductor must have a higher resistance
100
This time, the ohmic conductors are connected in parallel. Assuming they have the same value of resistance, what can be inferred about the current passing through each conductor?
The current through both conductors is the same
101
In a series circuit:
- Current is the same at all points of the circuit.
- The total potential difference of the power supply is shared between the components.
- Therefore by Ohm's law, the component with the larger share of potential difference must be the component with the larger resistance.
102
In a parallel circuit:
- The current is split between the branches.
- The potential difference across each parallel-connected component is the same.
- Therefore by Ohm's law, the current must be the same through two components of the same resistance connected in parallel.
103
What will happen to a bulb that is connected in series with a thermistor, as the temperature on the thermistor changes?
- At high temperatures, the bulb glows brighter
- At high temperatures, there is a higher potential difference across the bulb
104
The electric current of alternating current (a.c)
repeatedly …
changes direction.
105
This mains electricity supply has a frequency of ——— and is about 230 V.
50 Hz
106
This mains electricity supply has a frequency of 50 Hz and is about ——- V.
230
107
The electric current of direct current flows in …
only one direction.
108
—————- are sources of direct current.
Batteries and cells
109
Batteries and cells are sources of ...
direct current
110
In the UK, the electricity from the plug sockets (mains) is ———— current.
alternating
111
What is Direct current (d.c.)?
the electric current flows in only one direction.
112
What is Alternating current (a.c)?
the electric current repeatedly changes direction.
113
The neutral wire is ...
blue
114
The neutral wire is at or close to …
earth potential (which is 0V).
115
The ——— wire is at or close to earth potential (which is 0V).
neutral
116
The neutral wire completes …
the circuit and carries current away from the appliance.
117
The live wire is ——— and carries a 230V potential.
brown
118
The live wire is brown and carries a ——— potential.
230V
119
The live wire provides …
the alternating potential difference from the mains electricity supply.
120
The earth wire has …
green and yellow stripes.
121
The earth wire has a 1. potential and only 2.
1. 0V
2. carries a current if there is a fault.
122
The earth wire is a …
safety wire to stop the appliance becoming live.
123
Which type of wire is there for safety?
Earth
124
What are the types of wires?
-neutral
-live
-earth
125
Appliances in the EU have a label or panel that tells you ….
what the power rating of the appliance is.
126
energy transferred =
charge x potential difference.
127
Power stations create …
an electric current, which is an energy carrier.
128
Large power stations are more efficient than smaller power stations because they can burn lots of fuel at very high temperatures. This creates …
very hot steam that can turn the turbines.
129
Large power stations are more efficient than smaller power stations because …
they can burn lots of fuel at very high temperatures.
130
Power stations produce electricity at a voltage of ——— Volts.
25,000
131
Step-up transformers then increase the potential difference to ——- Volts.
400,000
132
Step-up transformers reduce the 1. and this reduces …
1. current
2. how much heat is lost when it’s being transported across the country.
133
Step-up reduces the current and this reduces how much heat is lost when it’s being transported across the country. This …
increases the efficiency of the National Grid system.
134
To get electricity to a safer voltage (230 Volts) in our homes, ——————- reduce the voltage to a lower value
step-down transformers
135
The National Grid is the …
network of cables and transformers that connect power stations with houses and shops in the United Kingdom.
136
Fuses contain a …
thin wire that melts if the current flowing through an appliance is too high.
137
Fuses contain a thin wire that melts if the current flowing through an appliance is too high.
This breaks the circuit and stops …
the flow of electric current.
138
Fuses and circuit breakers protect us from …
electrical appliances by stopping the flow of electric current flow if it gets too high.
139
Fuses and circuit breakers protect us from electrical appliances by stopping the flow of electric current flow if it gets too high. This stops the appliance …
overheating.
140
Circuit breakers are special devices that …
switch off the flow of current if the current is higher than a certain value.
141
Circuit breakers do the same job as fuses but …
can be used lots of times.
142
Give examples of appliance safety measures.
- fuse
- circuit beakers
143
Fuse ratings tell us the …
level where a fuse will begin to melt.
144
Circuit breakers also break circuits ——- than fuses. This reduces the risk of getting an electric shock even more.
faster
145
Lots of electrical appliances, such as toasters and microwave ovens, have ——- casings.
metal
146
Lots of electrical appliances, such as toasters and microwave ovens, have metal casings.
If there is a fault in the appliance, …
one of the wires may touch the metal case.
147
An earth wire is a —— resistance wire that connects the metal case to the ground.
low
148
An earth wire is a low resistance wire that connects the metal case to the ...
ground
149
An earth wire is a low resistance wire that connects the metal case to the ground.
If the casing is touched by a wire inside the appliance, …
the current will flow through the earth wire.
150
Because the resistance of the earth wire is low, a —————- will flow through it, breaking the fuse in the device. This will stop the flow of current and make the appliance safe.
very high current
151
Because the resistance of the earth wire is low, a very high current will flow through it, breaking the fuse in the device. This will …
stop the flow of current and make the appliance safe.
152
A live wire can still be dangerous when the mains switch is open (i.e. the plug socket or light switch is turned off).
This is because …
it might still hold some potential difference.
153
If you touched the live wire, your body would supply a link between the supply and the ground.
This is an …
electric shock.
154
The live wire and the earth wire can never be in contact because …
this would remove the safety feature of the earth wire.
155
The live wire carries a large amount of ————- energy so can be dangerous.
electrical
156
What kind of appliance casing requires an earth wire?
Metal
157
Objects become charged when they —————. Charge is measured in Coulombs (C).
gain or lose electrons.
158
Like charges ——- each other.
repel
159
Two positive charges will —— each other.
repel
160
Two negative charges will also ——— each other.
repel
161
When there is a difference between the positive and negative charge of two objects, there is a —————-between the two objects.
potential difference
162
When there is a difference between the positive and negative charge of two objects, there is a potential difference between the two objects. This potential difference causes …
a rapid transfer of charge.
163
When there is a difference between the positive and negative charge of two objects, there is a potential difference between the two objects. This potential difference causes a rapid transfer of charge. Energy is stored in an 1. store and a 2. is produced.
1. electrostatic
2. spark
164
Rubbing an object against another object can cause electrons to jump from one object to the other. This causes both objects to become ...
charged
165
Conductors allow charge to flow to earth, so they …
would not maintain (keep) this charge.
166
We call objects with no conducting path (link) to earth …
isolated objects.
167
A plastic rod will be charged by rubbing it with a cloth. It will then, attract or repel other charged objects depending on …
their charge.
168
Static electricity arises when …
electrons transfer from one object to another.
169
One object becomes positive, one becomes negative.
This results in …
a static electric force between the objects.
170
Charged objects create ————————, just like magnets create magnetic fields around themselves.
invisible electric fields around themselves
171
If another electrically charged object enters an electric field, the charged object will …
feel a force acting on it.
172
The direction of an electric field is the direction that …
a positively charged object would move at that point in the field.
173
The direction of an electric field is shown on a diagram by …
arrows drawn onto the electric field lines.
174
The closer an object is to the charged object, the ———- the electric field.
stronger
175
The higher the charge of the object, the ——— the electric field.
stronger
176
Charged objects create …
electric fields around them.
177
Electric field lines are drawn to display …
an electric field on a diagram.
178
Each electric field line shows the direction that a ———— charged object would move at that point.
positively
179
The electric field lines around tiny positively charged and negatively charged objects are called ‘—————'.
point charges
180
Which particle is transferred to produce static electricity?
Electrons
