What happens to the total resistance of a circuit when two or more resistors are connected in parallel?

The total resistance decreases and is less than the resistance of any individual resistor, because each extra resistor gives the charge an additional pathway to flow along.

Explain why connecting resistors in series increases the total resistance.

Charge must flow through multiple components , so it experiences a higher number of collisions , increasing the overall resistance.

Explain why connecting resistors in parallel decreases the total resistance.

Each resistor provides an extra pathway for charge to flow, so only some of the charge flows along each path, giving a smaller overall resistance.

In a series circuit, increasing the number of resistors ______ the overall resistance.

In a series circuit, increasing the number of resistors increases the overall resistance.

True or False? Two resistors connected in parallel have a greater combined resistance than the same two resistors connected in series.

False. The combined resistance in parallel is less than in series, because there is more than one pathway for the charge to flow.

How does current behave in a series circuit compared with a parallel circuit?

In a series circuit, the current is the same at every point. In a parallel circuit, the current splits at junctions, with some flowing along each path.

How does potential difference behave in a series circuit compared with a parallel circuit?

In a series circuit, the potential difference of the supply is shared between the components. In a parallel circuit, the potential difference across each component is the same .

How does the total resistance of two resistors connected in series compare with the same two resistors connected in parallel?

In series , the total resistance is greater than either individual resistance. In parallel , the total resistance is smaller than either individual resistance.

Define series circuit .

A circuit consisting of a string of components connected in the same loop to a power supply.

Name two disadvantages of connecting components in a series circuit.

Any two from: if one component breaks, all the others stop working, and the components cannot be controlled (switched on and off) separately.

In a series circuit, the potential difference of the power supply is ______ between the components.

In a series circuit, the potential difference of the power supply is shared between the components.

True or False? In a series circuit, the current is different at each point around the loop.

False. Current is the same at all points in a series circuit — it does not split as it does in a parallel circuit.

Describe the I-V graph for a fixed resistor.

A straight line through the origin — current is directly proportional to potential difference because the resistance is constant .

Why does the I-V graph for a filament lamp curve rather than form a straight line?

As current increases, the filament's temperature increases , causing the metal lattice atoms to vibrate more. This makes it harder for free electrons to pass through, so resistance increases and current rises at a slower rate.

Describe the I-V graph for a diode.

In forward bias , current increases sharply once a threshold potential difference is reached. In reverse bias , almost no current flows, even as the potential difference increases.

True or False? Reversing the potential difference across a filament lamp changes the shape of its I-V graph.

False. Reversing the potential difference reverses the current but makes no difference to the shape of the curve.

A light-dependent resistor — a sensory resistor whose resistance changes depending on the light intensity falling on it.

How does the resistance of an LDR change as light intensity increases?

The resistance decreases as light intensity increases, and vice versa.

Define a thermistor .

A sensory resistor whose resistance changes depending on its temperature .

As the temperature of a thermistor increases, its resistance ______ .

As the temperature of a thermistor increases, its resistance decreases .

Give one everyday use of an LDR and one everyday use of a thermistor.

LDRs are used in light sensors, for example street lighting and garden lights. Thermistors are used as temperature sensors, for example in ovens, fire alarms and digital thermometers.

In the circuit used to test how resistance varies in a filament lamp or diode, what is the independent variable, and what is used to change it?

The current is the independent variable, and it is changed using the variable resistor .

In the circuit used to test how resistance varies in a filament lamp or diode, what is the dependent variable, and what is used to measure it?

The voltage is the dependent variable, measured using the voltmeter connected across the component.

Describe how the circuit is used to investigate how the resistance of an LDR changes.

Starting in a dark room with the lamp off, the voltmeter and ammeter readings are recorded. The light intensity is then slowly increased using a dimmer switch, and readings are taken at each increase.

Describe how the circuit is used to investigate how the resistance of a thermistor changes.

Starting with the heater off, the voltmeter and ammeter readings are recorded. The temperature is then slowly increased using the heater, and readings are taken at each increase.

The ammeter is connected in ______ with the component being tested.

The ammeter is connected in series with the component being tested.

Why should a low-voltage power supply (below 15 V) be used when testing a component?

A higher current would cause the temperature of the component to rise, which would affect its resistance and distort the results.

True or False? The voltmeter should be connected in series with the component being tested.

False. The voltmeter is connected in parallel with the component; it is the ammeter that is connected in series.

What are the independent and dependent variables in the experiment investigating potential difference, current and resistance for a resistor and a filament lamp?

The independent variable is potential difference, V , and the dependent variable is current, I .

Why is the circuit switched off between readings when testing a component?

To prevent heating of the component and wires, which would otherwise affect the resistance and the accuracy of the results.

In the experiment testing series and parallel circuits, how does the total resistance of two resistors in series compare with the same two resistors in parallel?

In series , the total resistance is the sum of the two resistances. In parallel , the total resistance is less than either individual resistance.

Define a zero error .

A systematic error caused by an instrument, such as a voltmeter or ammeter, not reading zero when it should, leading to inaccurate readings.

Give two random errors that could affect the experiment testing series and parallel circuits.

Random errors that could affect the experiment include: The voltmeter and ammeter may have some resistance of their own Changes in the temperature of the equipment affect resistance Variation between repeated current readings

The power supply should be ______ between readings to prevent the components from overheating.

The power supply should be disconnected between readings to prevent the components from overheating.

True or False? The voltmeter and ammeter do not need to start from zero before taking readings.

False. The voltmeter and ammeter should start from zero to avoid a zero error in the readings.

State two safety considerations when carrying out the experiment testing series and parallel circuits.

Safety considerations when carrying out the experiment include: Avoiding touching the wire directly when the circuit is switched on Switching off the power supply immediately if a burning smell is present Keeping liquids away from the equipment Taking care when handling hot components, especially the filament lamp

GCSEPhysicsEdexcelFlashcards10. Electricity & CircuitsComponents in Series & Parallel Circuits

Components in Series & Parallel Circuits (Edexcel GCSE Physics): Flashcards

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What happens to the total resistance of a circuit when two or more resistors are connected in series?

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Cards in this collection (39)

What happens to the total resistance of a circuit when two or more resistors are connected in series?
The total resistance increases. It is equal to the sum of the individual resistances: $R = R_{1} + R_{2} + R_{3}$
What happens to the total resistance of a circuit when two or more resistors are connected in parallel?
The total resistance decreases and is less than the resistance of any individual resistor, because each extra resistor gives the charge an additional pathway to flow along.
Explain why connecting resistors in series increases the total resistance.
Charge must flow through multiple components, so it experiences a higher number of collisions, increasing the overall resistance.
Explain why connecting resistors in parallel decreases the total resistance.
Each resistor provides an extra pathway for charge to flow, so only some of the charge flows along each path, giving a smaller overall resistance.
In a series circuit, increasing the number of resistors ______ the overall resistance.
In a series circuit, increasing the number of resistors increases the overall resistance.
True or False?
Two resistors connected in parallel have a greater combined resistance than the same two resistors connected in series.
False.
The combined resistance in parallel is less than in series, because there is more than one pathway for the charge to flow.
A series circuit has resistors of resistance 30 Ω and 10 Ω. If the combined resistance of the circuit is 60 Ω, what is the resistance of the third resistor, R₂?
$R_{2} = R - R_{1} - R_{3} = 60 - 30 - 10 = 20 Ω$
A cell supplies a current of 2 A to a series circuit containing a fixed resistor of resistance 4 Ω. What is the reading on a voltmeter connected across the resistor?
$V = I R = 2 \times 4 = 8 V$
How does current behave in a series circuit compared with a parallel circuit?
In a series circuit, the current is the same at every point. In a parallel circuit, the current splits at junctions, with some flowing along each path.
How does potential difference behave in a series circuit compared with a parallel circuit?
In a series circuit, the potential difference of the supply is shared between the components. In a parallel circuit, the potential difference across each component is the same.
How does the total resistance of two resistors connected in series compare with the same two resistors connected in parallel?
In series, the total resistance is greater than either individual resistance. In parallel, the total resistance is smaller than either individual resistance.
Define series circuit.
A circuit consisting of a string of components connected in the same loop to a power supply.
Name two disadvantages of connecting components in a series circuit.
Any two from: if one component breaks, all the others stop working, and the components cannot be controlled (switched on and off) separately.
In a series circuit, the potential difference of the power supply is ______ between the components.
In a series circuit, the potential difference of the power supply is shared between the components.
True or False?
In a series circuit, the current is different at each point around the loop.
False.
Current is the same at all points in a series circuit — it does not split as it does in a parallel circuit.
Describe the I-V graph for a fixed resistor.
A straight line through the origin — current is directly proportional to potential difference because the resistance is constant.
Why does the I-V graph for a filament lamp curve rather than form a straight line?
As current increases, the filament's temperature increases, causing the metal lattice atoms to vibrate more. This makes it harder for free electrons to pass through, so resistance increases and current rises at a slower rate.
Describe the I-V graph for a diode.
In forward bias, current increases sharply once a threshold potential difference is reached. In reverse bias, almost no current flows, even as the potential difference increases.
True or False?
Reversing the potential difference across a filament lamp changes the shape of its I-V graph.
False.
Reversing the potential difference reverses the current but makes no difference to the shape of the curve.
Define an LDR.
A light-dependent resistor — a sensory resistor whose resistance changes depending on the light intensity falling on it.
How does the resistance of an LDR change as light intensity increases?
The resistance decreases as light intensity increases, and vice versa.
Define a thermistor.
A sensory resistor whose resistance changes depending on its temperature.
As the temperature of a thermistor increases, its resistance ______.
As the temperature of a thermistor increases, its resistance decreases.
Give one everyday use of an LDR and one everyday use of a thermistor.
LDRs are used in light sensors, for example street lighting and garden lights. Thermistors are used as temperature sensors, for example in ovens, fire alarms and digital thermometers.
In the circuit used to test how resistance varies in a filament lamp or diode, what is the independent variable, and what is used to change it?
The current is the independent variable, and it is changed using the variable resistor.
In the circuit used to test how resistance varies in a filament lamp or diode, what is the dependent variable, and what is used to measure it?
The voltage is the dependent variable, measured using the voltmeter connected across the component.
Describe how the circuit is used to investigate how the resistance of an LDR changes.
Starting in a dark room with the lamp off, the voltmeter and ammeter readings are recorded. The light intensity is then slowly increased using a dimmer switch, and readings are taken at each increase.
Describe how the circuit is used to investigate how the resistance of a thermistor changes.
Starting with the heater off, the voltmeter and ammeter readings are recorded. The temperature is then slowly increased using the heater, and readings are taken at each increase.
The ammeter is connected in ______ with the component being tested.
The ammeter is connected in series with the component being tested.
Why should a low-voltage power supply (below 15 V) be used when testing a component?
A higher current would cause the temperature of the component to rise, which would affect its resistance and distort the results.
True or False?
The voltmeter should be connected in series with the component being tested.
False.
The voltmeter is connected in parallel with the component; it is the ammeter that is connected in series.
What are the independent and dependent variables in the experiment investigating potential difference, current and resistance for a resistor and a filament lamp?
The independent variable is potential difference, V, and the dependent variable is current, I.
Why is the circuit switched off between readings when testing a component?
To prevent heating of the component and wires, which would otherwise affect the resistance and the accuracy of the results.
In the experiment testing series and parallel circuits, how does the total resistance of two resistors in series compare with the same two resistors in parallel?
In series, the total resistance is the sum of the two resistances. In parallel, the total resistance is less than either individual resistance.
Define a zero error.
A systematic error caused by an instrument, such as a voltmeter or ammeter, not reading zero when it should, leading to inaccurate readings.
Give two random errors that could affect the experiment testing series and parallel circuits.
Random errors that could affect the experiment include:
- The voltmeter and ammeter may have some resistance of their own
- Changes in the temperature of the equipment affect resistance
- Variation between repeated current readings
The power supply should be ______ between readings to prevent the components from overheating.
The power supply should be disconnected between readings to prevent the components from overheating.
True or False?
The voltmeter and ammeter do not need to start from zero before taking readings.
False.
The voltmeter and ammeter should start from zero to avoid a zero error in the readings.
State two safety considerations when carrying out the experiment testing series and parallel circuits.
Safety considerations when carrying out the experiment include:
- Avoiding touching the wire directly when the circuit is switched on
- Switching off the power supply immediately if a burning smell is present
- Keeping liquids away from the equipment
- Taking care when handling hot components, especially the filament lamp

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