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AQA GCSE Physics > Topic 2: Electricity > Flashcards

Topic 2: Electricity Flashcards

(73 cards)

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1
Q

What is the function of a cell/battery in a circuit?

A

It provides the circuit with a source of potential difference (voltage). A battery consists of two or more cells.

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2
Q

What is the purpose of a switch in a circuit?

A

It turns the circuit on (closed) or off (open).

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3
Q

What is a fixed resistor, and what does it do?

A

A fixed resistor limits the flow of current and has a resistance that cannot change.

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4
Q

How does a variable resistor work, and where is it commonly used?

A

A variable resistor has a slider that changes its resistance. It is often used in dimmer switches and volume controls.

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5
Q

How does a thermistor’s resistance change with temperature?

A

As temperature increases, its resistance decreases, and vice versa.

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6
Q

How does an LDR’s resistance change with light intensity?

A

As light intensity increases, its resistance decreases, and vice versa.

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7
Q

What is the function of a diode in a circuit?

A

A diode allows current to flow in one direction only (forward bias) and is used to convert AC to DC.

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8
Q

What is an LED, and where is it commonly used?

A

An LED is a light-emitting diode that emits light when current passes through it. It is used in aviation lighting, displays, TVs, and road signs.

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9
Q

How is an ammeter connected in a circuit, and what does it measure?

A

An ammeter is connected in series and measures current. Its resistance is considered negligible.

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10
Q

How is a voltmeter connected in a circuit, and what does it measure?

A

A voltmeter is connected in parallel and measures potential difference (voltage). Its resistance is considered infinite.

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11
Q

What are the three essential requirements for an electric circuit diagram to work effectively?

A

1) An energy source (e.g., cell, battery, or power supply).
2) A closed path or complete circuit.
3) Electrical components (e.g., sensors, measuring devices, or energy converters).

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12
Q

What is the key rule for connecting an ammeter in a circuit?

A

An ammeter is always connected in series.

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13
Q

What is the key rule for connecting a voltmeter in a circuit?

A

A voltmeter is always connected in parallel to the component being measured

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14
Q

What is the direction of current flow in a circuit?

A

Current flows from the positive to the negative terminal of the power supply.

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15
Q

How does a diode ensure current flows in only one direction?

A

A diode is forward-biased when its positive side is connected to the positive terminal of the power supply, allowing current to flow.

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16
Q

What should you remember when drawing circuit diagrams?

A
  • Use straight lines for wires (use a ruler).
  • Draw symbols neatly and accurately.
  • Ensure the diagram is clear and unambiguous.
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17
Q

What happens if a switch in a circuit is open?

A

The circuit is incomplete, and no current flows.

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18
Q

What is the resistance of an ammeter and a voltmeter assumed to be in exam questions?

A

Ammeter: Negligible resistance.
Voltmeter: Infinite resistance.

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19
Q

What is potential difference?

A

Potential difference (p.d.) is the energy transferred per unit charge flowing from one point to another in a circuit. It is also called voltage and is measured in volts (V).

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20
Q

What are the sources of potential difference?

A

Sources include:
- A cell
- Batteries (multiple cells)
- Electrical generators

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21
Q

What does a cell do in a circuit?

A

A cell makes one end of the circuit positive and the other negative, setting up a potential difference across the circuit.

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22
Q

What is the unit of potential difference?

A

The unit is volts (V), which is equivalent to joules per coulomb (J /C).

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23
Q

How is potential difference measured?

A

It is measured using a voltmeter, which is always connected in parallel to the component being measured.

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24
Q

What is the equation for potential difference?

A

V=W/Q, where:
V = potential difference (V)
W = work done or energy transferred (J)
Q = charge (C)

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25
Calculate the work done to move 5 C of charge through a p.d. of 20 V.
W=VQ W=20×5=100J
26
What is electric current?
Electric current is the flow of electrical charge, measured in amperes (A) or amps.
27
What is the symbol for current?
The symbol is I.
28
What is the unit of charge?
The unit of charge is the coulomb (C), where 1C=1A×1s
29
What is the relationship between charge, current, and time?
Q=It, where: Q = charge (C) I = current (A) t = time (s)
30
Calculate the current when 4 C of charge passes through a lamp in 500 s.
I=Q/t I=4/500 = 0.008A  
31
What is the direction of electron flow in a circuit?
Electrons flow from the negative terminal to the positive terminal of a cell.
32
What is conventional current?
Conventional current is defined as the flow of positive charge from the positive terminal to the negative terminal, opposite to electron flow.
33
How is current measured?
Current is measured using an ammeter, which is always connected in series with the circuit.
34
How many electrons are in one coulomb of charge?
1C=6.24×10¹⁸ electrons.
35
What is the difference between charge and current?
Charge is a quantity of electrons (measured in coulombs), while current is the rate of flow of charge (measured in amperes).
36
What does an ammeter measure?
An ammeter measures the number of electrons (or charge) flowing through it per second, which is the current.
37
What are the two types of resistor?
- Fixed - Variable
38
What are the difference between fixed and variable resistors?
- Fixed resistors have a resistance that remains constant - Variable resistors can change the resistance through the circuit
39
What is Ohm's Law?
The current through a conductor is directly proportional to the potential difference across it
40
What are electrical conductors which obey Ohm's Law called?
Ohmic Conductors
41
What are some examples of Ohmic Conductors?
- Fixed Resistors - Wires - Heating Elements
42
What is the equation for Ohm's Law?
V = IR - If V and I are directly proportional, that means R is constant
43
Where is Ohm's Law only relevant at?
Constant Temperatures
44
What will an I-V graph look like for an ohmic conductor?
Straight Line through the origin
45
What is a filament lamp in terms of Ohm's Law?
- NON-ohmic conductor - Current and potential difference are not directly proportional as resistance of the filament lamp increases as the temperature of the filament increases
46
What is the I-V graph for a filament lamp and what does it show?
- S Curve - Current increasing at a proportionally slower rate to potential difference
47
Why is current moving slower than potential difference in a filament lamp?
- Current increases, temp of filament increases - Atoms in metal lattice of filament vibrate more - Increase in resistance as difficult for free electrons to pass through - Resistance opposes current, causing current to increase slower
48
What is electric current in a material?
Electric current is the flow of free electrons in a material.
49
What is the relationship between temperature and resistance in a material?
An increase in temperature causes an increase in resistance.
50
What is a diode in terms of Ohm's Law?
- Non-Ohmic Conductor that allows current flow in one direction only - Forward Bias
51
What happens if current goes in the reverse direction of a diode?
- Diode has high resistance and no current flows - Reverse Bias
52
What will an I-V graph look like for a diode?
Flat till origin, before increasing
53
What does it mean for a circuit element to be linear?
A linear element has an I-V graph that is a straight line passing through the origin. It obeys Ohm's Law and has a constant resistance.
54
What does it mean for a circuit element to be non-linear?
A non-linear element has an I-V graph that is not a straight line. It does not obey Ohm's Law, and its resistance changes with voltage or current.
55
How can you determine if a component is linear or non-linear?
Check its I-V graph. If it’s a straight line through the origin, it’s linear. If not, it’s non-linear.
56
Name three examples of non-linear components.
- Filament lamps - Diodes & LEDs - LDRs (Light Dependent Resistors) and Thermistors
57
Can a component be linear in some conditions and non-linear in others?
Yes. For example, a fixed resistor is linear at low currents but can become non-linear at high currents (due to temperature changes).
58
What are the characteristics of a series circuit?
- Current is same at all points I₁ = 1₂ = I₃ - Total potential difference of power supply is shared between components (e.g 2 bulbs total 12V, both have 6V) - Total resistance of two components is sum of resistance R + R = 2R, Total R = 2R
59
What are the characteristics of a parallel circuit?
- Total current is sum of current through separate components ( I = I₁ + I₂) - Potential difference across components is the same (e.g. 2 bulbs total 12V, each have 12V) - Total resistance of two resistors is less than resistance of the smallest individual resistor (1/R₁ + 1/R₂ = 1/R)
60
Why do currents not split equally but behave in this way?
- Flow of electrons which are physical matter, meaning cannot be destroyed/created meaning total number of electrons remains the same and when reaching a junction, some will go one way and the rest will go the other
61
Why does overall resistance increase with resistors?
The more resistors there are, the more the charge must pass through
62
Why does two resistors in parallel decrease the combined resistance?
Each resistor creates an extra path along which charge can flow which allows for more charge to flow overall and leads to smaller resistance
63
What are the advantages of setting up resistors in parallel?
- Components are individually controlled, using their own circuits - If one component stops working others will continue to function
64
What happens to current in a series circuit?
The current is the same at all points in the circuit
65
What happens to current in a parallel circuit?
The current splits at junctions into different paths
66
How is voltage distributed in a series circuit?
The voltage of the power supply is shared between components
67
How is voltage distributed in a parallel circuit?
The voltage across each component is the same
68
How is total resistance calculated in a series circuit?
Total resistance = Sum of individual resistances (R_total = R1 + R2 + R3)
69
How is total resistance calculated in a parallel circuit?
Total resistance is less than the smallest individual resistance
70
Why is resistance higher in a series circuit?
Charge has to push through multiple components, increasing collisions
71
Why is resistance lower in a parallel circuit?
Charge has multiple pathways to flow, reducing overall resistance
72
What happens to overall resistance when two resistors are connected in series?
The total resistance increases
73
What happens to overall resistance when two resistors are connected in parallel?
The total resistance decreases

AQA GCSE Physics (6 decks)

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