Topic 9 - Electricity and Circuits COMPLETE PK Flashcards
1 What word describes materials that electricity will pass through?
conductors
2 What word describes materials that electricity cannot pass through?
insulators
3 What components do you need to make a circuit that would make a small torch bulb light up?
battery, connecting wires, lamp; switch is optional
4 What are the two terminals of an electric cell labelled as?
plus and minus
5 In an electric circuit with a battery, which of these materials will conduct: copper, wood, salty water?
copper and salty water
6 Which of these materials are insulators: plastic, metal, air?
plastic and air
7 What component is used to measure current?
ammeter
8 What name is given to the negatively charged subatomic particles that cause an electric current?
electrons
9 Is mains voltage about 15 times, 150 times or 1500 times bigger than the voltage from a battery?
about 150 times
10 If you connect some cells together in series, what is formed?
a battery
11 What is the name of a circuit with one path around it and no branches?
a series circuit
12 What is the name given to a circuit with components in different branches?
a parallel circuit
13 What is the circuit symbol for a lamp?
circle with a cross in it
14 What is the circuit symbol for a cell?
two vertical lines, one longer than the other
15 How can you tell which is the negative terminal of a cell from the circuit symbol?
It is the shorter line.
16 What is the difference between conventional current and the flow of electrons?
Electrons flow from the negative terminal of a cell to the positive terminal, conventional current flows the other way.
17 What unit is current measured in?
amps/amperes
18 What is another term for potential difference?
voltage
19 Which component is used to measure electric current?
an ammeter
20 What are the units for current?
amps or amperes
21 What two conditions are needed to give a current in a circuit?
closed circuit and potential difference
22 Is an ammeter connected in parallel or in series with a component?
series
23 A series circuit has two lamps. When the current through one lamp is 2A, what is the current through the other lamp?
2A
24 A parallel circuit has two lamps in parallel. When the current through each lamp is 2A, what is the current from the battery?
4A
25 Which component is used to measure potential difference?
a voltmeter
26 What are the units for potential difference?
volts
27 Current can be described as the rate of flow of charge. In a metal, what are the charged particles that flow?
electrons
28 In a circuit, energy is transferred to a charge. Where is this energy transferred from?
cell/battery/power supply
29 What is an electric current?
a flow of charge
30 State the unit and the symbol for current.
amp/ampere, A
31 State the unit and the symbol for charge.
coulomb, C
32 Write down the equation relating the total charge that flows to current and time.
Q = I x t
33 State the unit and the symbol for potential difference.
volt, V
34 How many volts is one joule per coulomb?
1V
35 Write down the equation relating the energy transferred in a circuit to the potential difference.
E = Q x V
36 Describe the potential difference between two points in terms of energy transferred.
It is the energy transferred when 1 coulomb of charge moves from one point to the other.
37 State the unit for electrical resistance.
ohm
38 Write down the equation that is used to work out electrical resistance.
R = V / I
39 What unit is used to measure resistance?
ohms
40 What is the symbol for a resistor?
a rectangle
41 What is the symbol for a variable resistor?
a rectangle with an arrow through it
42 What equation connects potential difference, current and resistance?
V = I x R
43 A circuit contains a resistor. If another resistor is added in series with the first, does the total resistance in the circuit increase, decrease or stay the same?
increase
44 A circuit contains a resistor. If another resistor is added in parallel with the first, does the total resistance in the circuit increase, decrease or stay the same?
decrease
45 When resistors are connected in series, how can you calculate the total resistance?
add the resistances together
46 When the potential difference across a fixed resistor is doubled, what happens to the current?
the current doubles
47 What happens to the resistance of a light-dependent resistor LDR when light intensity increases?
It decreases
48 What happens to the resistance of a thermistor when the temperature increases?
it decreases
49 What is the name of a resistor that can be changed by adjusting a dial?
a variable resistor
50 Which component could be used to change the current in a circuit when the temperature changes?
a thermistor
51 Which component could be used to change the current in a circuit when the light intensity changes?
a light-dependent resistor
52 What does a diode do?
conducts electricity in only one direction
53 What happens to the resistance of a filament lamp when the potential difference is increased?
it increases
54 What happens to the resistance of a thermistor when the temperature rises?
it decreases
55 What happens to the resistance of a light-dependent resistor when the light intensity increases?
it decreases
56 What does the graph of current against potential difference look like for a fixed resistor?
straight line through the origin/directly proportional relationship
57 When an electric current passes through a high-resistance wire, what happens to the wire?
it becomes hot
58 How can resistance in the wires in circuits be reduced?
cool the wire / use low-resistance wire / make the wire thicker / make the wires as short as possible
59 Give an example of an appliance that uses the heating effect of a current.
e.g. kettle
60 Give an example of a disadvantage that can result from overheating by an electric current.
e.g. fire, damage to the appliance/wires
61 If the new connecting wires in a house have a lower resistance than the old ones, what effect will this have on daily electricity use?
it will be less
62 When electrons move through a lattice of positive ions, what happens to cause electrical resistance?
collisions
63 When a resistor heats up, what happens to the positive ions to increase resistance?
they vibrate more
64 What is the equation that connects energy transferred to current, potential difference and time?
E = I x V x t, energy transferred = current x potential difference x time