A relay is an electromagnetic component that uses a small current in one circuit to switch on a much larger current in another circuit.

A fuse is a safety component that protects expensive components from current surges and acts as a safety measure against fire.

Define a light-emitting diode (LED) .

An LED is a type of semiconductor diode that emits light when current flows through it in a specific direction.

How are ammeters and voltmeters connected in a circuit?

Ammeters are always connected in series ; voltmeters are always connected in parallel .

What is the purpose of resistors, potential dividers, thermistors and LDRs in a circuit?

They are all used to control the current in a circuit.

Under what condition will an LED emit light?

An LED emits light only when it is forward biased , meaning current flows through it in the same direction as conventional current (positive to negative).

Ammeters are always connected in ______ , whilst voltmeters are always connected in ______ .

Ammeters are always connected in series , whilst voltmeters are always connected in parallel .

True or False? An LED will emit light regardless of the direction of current flowing through it.

False. An LED only emits light when forward biased (current flowing in the same direction as the triangle in its circuit symbol); it emits no light when connected the opposite way round.

Define a series circuit .

A series circuit is a closed-loop circuit in which the components are connected one after another, so the current is the same at every point .

Define a parallel circuit .

A parallel circuit consists of two or more components connected along separate branches .

What two factors determine the size of the current flowing around a series circuit?

The voltage of the power source and the resistance of the components in the circuit.

What happens to the current in a series circuit as more components are added?

The current decreases , because adding components increases the total resistance of the circuit.

What is true of the current entering and leaving a junction in a parallel circuit?

The current is conserved — the total current flowing into the junction equals the total current flowing out of it.

Give two advantages of connecting components in parallel rather than in series.

Components can be individually controlled using their own switches, and if one component stops working, the others continue to function .

The current in each branch of a parallel circuit is only identical if the ______ of the components in each branch is identical.

The current in each branch of a parallel circuit is only identical if the resistance of the components in each branch is identical.

True or False? Current is a physical substance that gets used up as it flows around a circuit.

False. Current is the flow of electrons ; electrons cannot be created or destroyed, so the total current is conserved around the circuit, not used up.

In a series circuit, how does the sum of the potential differences across the components compare with the potential difference of the power supply?

They are equal — the sum of the potential differences across the components equals the total potential difference of the power supply.

How does the potential difference compare across the different branches of a parallel circuit?

The potential difference across each branch is the same .

In a parallel circuit, if one branch contains components connected in series, how is the potential difference shared between them?

It is split between the components in that branch, following the same rule as a series circuit (the pds across the components in the branch sum to the pd across the whole branch).

In a series circuit, the sum of the potential differences across each component is equal to the ______ of the power supply.

In a series circuit, the sum of the potential differences across each component is equal to the potential difference of the power supply.

True or False? In a parallel circuit with a 12 V battery connected to two lamps on separate branches, the potential difference across each lamp is 6 V.

False. The potential difference across each lamp is 12 V , the same as the supply — parallel branches each get the full supply pd, they do not divide it as in a series circuit.

Define combined resistance .

The combined resistance is the total resistance of two or more resistors connected together, treated as a single resistor.

How do you find the combined resistance of resistors connected in series ?

The combined resistance is equal to the sum of the individual resistances of the resistors.

How does the combined resistance of resistors connected in parallel compare with the resistance of any individual resistor?

The combined resistance decreases and is less than the resistance of any of the individual resistors.

If two resistors of equal resistance are connected in parallel, what is the combined resistance?

The combined resistance is half the resistance of one of the individual resistors.

When two or more resistors are connected in series, the combined resistance is equal to the ______ of their individual resistances.

When two or more resistors are connected in series, the combined resistance is equal to the sum of their individual resistances.

True or False? Connecting two identical resistors in parallel doubles the combined resistance.

False. Connecting two identical resistors in parallel halves the combined resistance, it does not double it.

Define a thermistor .

A thermistor is a non-ohmic conductor and sensory resistor whose resistance varies with temperature . Most are negative temperature coefficient (NTC), so resistance decreases as temperature increases .

Define a light-dependent resistor (LDR) .

An LDR is a non-ohmic conductor and sensory resistor whose resistance decreases as the light intensity falling on it increases.

Define a potentiometer .

A potentiometer is a variable resistor consisting of a coil of wire with a sliding contact , which divides it into an upper and lower part of different resistances.

How does the resistance of an LDR in the dark compare with its resistance in bright light?

In the dark, its resistance is very large (millions of ohms); in bright light, its resistance is small (tens of ohms).

Most thermistors are ______ temperature coefficient (NTC) components, meaning their resistance ______ as temperature increases.

Most thermistors are negative temperature coefficient (NTC) components, meaning their resistance decreases as temperature increases.

True or False? In a potential divider, the resistor with the largest resistance has the smallest share of the potential difference.

False. The resistor with the largest resistance gets the greatest share of the potential difference.

O LevelPhysicsCambridge (CIE)Flashcards4. Electricity & Magnetism4.3 Electric Circuits

4.3 Electric Circuits (Cambridge (CIE) O Level Physics): Flashcards

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Cards in this collection (35)

Define a relay.
A relay is an electromagnetic component that uses a small current in one circuit to switch on a much larger current in another circuit.
Define a fuse.
A fuse is a safety component that protects expensive components from current surges and acts as a safety measure against fire.
Define a light-emitting diode (LED).
An LED is a type of semiconductor diode that emits light when current flows through it in a specific direction.
How are ammeters and voltmeters connected in a circuit?
Ammeters are always connected in series; voltmeters are always connected in parallel.
What is the purpose of resistors, potential dividers, thermistors and LDRs in a circuit?
They are all used to control the current in a circuit.
Under what condition will an LED emit light?
An LED emits light only when it is forward biased, meaning current flows through it in the same direction as conventional current (positive to negative).
Ammeters are always connected in ______, whilst voltmeters are always connected in ______.
Ammeters are always connected in series, whilst voltmeters are always connected in parallel.
True or False?
An LED will emit light regardless of the direction of current flowing through it.
False.
An LED only emits light when forward biased (current flowing in the same direction as the triangle in its circuit symbol); it emits no light when connected the opposite way round.
Define a series circuit.
A series circuit is a closed-loop circuit in which the components are connected one after another, so the current is the same at every point.
Define a parallel circuit.
A parallel circuit consists of two or more components connected along separate branches.
What two factors determine the size of the current flowing around a series circuit?
The voltage of the power source and the resistance of the components in the circuit.
What happens to the current in a series circuit as more components are added?
The current decreases, because adding components increases the total resistance of the circuit.
What is true of the current entering and leaving a junction in a parallel circuit?
The current is conserved — the total current flowing into the junction equals the total current flowing out of it.
Give two advantages of connecting components in parallel rather than in series.
Components can be individually controlled using their own switches, and if one component stops working, the others continue to function.
The current in each branch of a parallel circuit is only identical if the ______ of the components in each branch is identical.
The current in each branch of a parallel circuit is only identical if the resistance of the components in each branch is identical.
True or False?
Current is a physical substance that gets used up as it flows around a circuit.
False.
Current is the flow of electrons; electrons cannot be created or destroyed, so the total current is conserved around the circuit, not used up.
In a series circuit, how does the sum of the potential differences across the components compare with the potential difference of the power supply?
They are equal — the sum of the potential differences across the components equals the total potential difference of the power supply.
How does the potential difference compare across the different branches of a parallel circuit?
The potential difference across each branch is the same.
In a parallel circuit, if one branch contains components connected in series, how is the potential difference shared between them?
It is split between the components in that branch, following the same rule as a series circuit (the pds across the components in the branch sum to the pd across the whole branch).
In a series circuit, the sum of the potential differences across each component is equal to the ______ of the power supply.
In a series circuit, the sum of the potential differences across each component is equal to the potential difference of the power supply.
True or False?
In a parallel circuit with a 12 V battery connected to two lamps on separate branches, the potential difference across each lamp is 6 V.
False.
The potential difference across each lamp is 12 V, the same as the supply — parallel branches each get the full supply pd, they do not divide it as in a series circuit.
Define combined resistance.
The combined resistance is the total resistance of two or more resistors connected together, treated as a single resistor.
How do you find the combined resistance of resistors connected in series?
The combined resistance is equal to the sum of the individual resistances of the resistors.
How does the combined resistance of resistors connected in parallel compare with the resistance of any individual resistor?
The combined resistance decreases and is less than the resistance of any of the individual resistors.
If two resistors of equal resistance are connected in parallel, what is the combined resistance?
The combined resistance is half the resistance of one of the individual resistors.
When two or more resistors are connected in series, the combined resistance is equal to the ______ of their individual resistances.
When two or more resistors are connected in series, the combined resistance is equal to the sum of their individual resistances.
True or False?
Connecting two identical resistors in parallel doubles the combined resistance.
False.
Connecting two identical resistors in parallel halves the combined resistance, it does not double it.
Define a thermistor.
A thermistor is a non-ohmic conductor and sensory resistor whose resistance varies with temperature. Most are negative temperature coefficient (NTC), so resistance decreases as temperature increases.
Define a light-dependent resistor (LDR).
An LDR is a non-ohmic conductor and sensory resistor whose resistance decreases as the light intensity falling on it increases.
Define a potentiometer.
A potentiometer is a variable resistor consisting of a coil of wire with a sliding contact, which divides it into an upper and lower part of different resistances.
How does the resistance of an LDR in the dark compare with its resistance in bright light?
In the dark, its resistance is very large (millions of ohms); in bright light, its resistance is small (tens of ohms).
State the potential divider equation for the output voltage of a two-resistor potential divider.
$V_{o u t} = (\frac{R_{1}}{R_{1} + R_{2}}) V_{i n}$
where V_out is the output voltage (V), V_in is the input voltage (V), and R₁, R₂ are the resistances (Ω) of the two resistors.
In a potential divider, R₁ = 20 kΩ and R₂ = 12 kΩ. If V_out = 5.3 V, calculate V_in.
$V_{i n} = V_{o u t} \times (\frac{R_{1} + R_{2}}{R_{1}}) = 5.3 \times (\frac{20 + 12}{20}) = 8.5 V (2 s.f.)$
Most thermistors are ______ temperature coefficient (NTC) components, meaning their resistance ______ as temperature increases.
Most thermistors are negative temperature coefficient (NTC) components, meaning their resistance decreases as temperature increases.
True or False?
In a potential divider, the resistor with the largest resistance has the smallest share of the potential difference.
False.
The resistor with the largest resistance gets the greatest share of the potential difference.

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