An ammeter is used to measure the current in a circuit. It is always connected in series with the component being measured.

A voltmeter is used to measure the potential difference across a component. It is always connected in parallel with the component being measured.

A fuse is a safety device that cuts off the flow of electricity to an appliance if the current becomes too large, by melting the fuse wire and breaking the circuit.

What does a diode do in a circuit?

A diode allows current to flow in one direction only. Current flows through it when it is in the forward bias position, and diodes are used to convert AC to DC current.

What three things does an electric circuit need to work effectively?

An energy source to provide potential difference, a closed path (complete circuit) for electrons to flow, and electrical components drawn with the correct circuit symbols.

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

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

True or False? Conventional current flows from the negative terminal to the positive terminal of a power supply.

False. Conventional current always flows from the positive terminal to the negative terminal of the power supply.

How does the resistance of a light-dependent resistor (LDR) change as light intensity increases?

As light intensity increases, the resistance of an LDR decreases.

Define potential difference .

Potential difference is the energy transferred per unit charge flowing from one point to another. It is measured in volts (V) .

Define electric current .

Electric current is the flow of electrical charge. It is the rate of flow of electrical charge, measured in amperes (A) .

The unit of charge is the ______ , equal to the quantity of electricity conveyed in one second by a current of one ampere.

The unit of charge is the coulomb , equal to the quantity of electricity conveyed in one second by a current of one ampere.

In which direction do electrons flow through a circuit?

Electrons flow away from the negative terminal of a cell towards the positive terminal. This is opposite to the direction of conventional current.

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

False. In a closed-loop circuit, the current is the same value at any point , because the same number of electrons per second passes through every part of the circuit.

State three sources of potential difference.

A cell , a battery (multiple cells), and an electrical generator .

Resistance is the opposition to current. The vibration of atoms in a wire slows down the flow of electrons; the higher the resistance, the lower the current.

The ohm (Ω) is the unit of resistance. One ohm is defined as one volt per ampere (1 V A⁻¹) .

The greater the resistance of a component, the ______ the current for a given potential difference.

The greater the resistance of a component, the lower the current for a given potential difference.

True or False? Good electrical conductors have a high resistance.

False. Good conductors have a low resistance, while insulators have a high resistance.

The resistance of which two circuit components is assumed to be negligible in exam questions?

The resistance of wires and batteries is assumed to be negligible in exam questions.

How does increasing the resistance of a component affect the current through it, for a constant potential difference?

The current decreases as the resistance increases, for a given potential difference.

In the experiment investigating resistance of a wire, what is the independent variable ?

The length of the resistance wire , L .

State two control variables in the experiment investigating resistance of a wire.

The potential difference of the power supply and the temperature of the wire.

What is the relationship between the resistance of a wire and its length?

Resistance is directly proportional to the length of the wire, shown by a straight line graph through the origin with a positive correlation.

How does the total resistance of two resistors connected in series compare to the sum of their individual resistances?

It is equal to the sum of the two individual resistances, as the current flows through just one path through both resistors.

How does the total resistance of two resistors connected in parallel compare to the sum of their individual resistances?

It is less than the sum of the two individual resistances, as the current is split between the different paths.

To reduce systematic errors, only allow ______ currents to flow through the wire so its temperature stays constant.

To reduce systematic errors, only allow small currents to flow through the wire so its temperature stays constant.

True or False? A zero error can occur if the first crocodile clip does not start at 0 on the ruler.

True. The first crocodile clip connected to the circuit must start at 0 on the ruler, otherwise this causes a zero error in the length measurements.

Define fixed resistor .

A fixed resistor has a resistance that remains constant .

Define variable resistor .

A variable resistor can change the resistance through a circuit, which varies the amount of current flowing through it.

For fixed and variable resistors, once the resistance is set, it stays at this value no matter how the ______ changes.

For fixed and variable resistors, once the resistance is set, it stays at this value no matter how the current changes.

Name four components (other than fixed and variable resistors) whose resistance changes with the current through them.

Lamps , diodes (including LEDs), thermistors and LDRs (light-dependent resistors).

True or False? Fixed resistors and variable resistors have the same circuit symbol.

False. Fixed and variable resistors have different circuit symbols.

Define ohmic conductor .

An ohmic conductor obeys Ohm's Law. At constant temperature, its resistance is constant and its I–V graph is a straight line through the origin .

The current through a conductor is directly proportional to the potential difference across it, at constant temperature.

Give three examples of ohmic conductors.

Fixed resistors , wires and heating elements .

Why does the resistance of a filament lamp increase as the current through it increases?

The increasing current raises the filament's temperature, causing the atoms in its metal lattice to vibrate more. This makes it harder for electrons to pass through, increasing resistance.

A diode allows current to flow in ______ direction only, called forward bias.

A diode allows current to flow in one direction only, called forward bias.

What happens to the current when a diode is in reverse bias?

In reverse bias, the diode has very high resistance, so no current flows .

True or False? A filament lamp is an example of an ohmic conductor.

False. A filament lamp is non-ohmic — its current and potential difference are not directly proportional.

Name four examples of non-linear circuit components.

Filament lamps , diodes and LEDs , LDRs and thermistors .

A thermistor is a non-ohmic conductor whose resistance depends on its temperature .

What happens to the resistance of a thermistor as its temperature increases?

As temperature increases , the resistance of a thermistor decreases .

True or False? A thermistor is an ohmic conductor.

False. A thermistor is a non-ohmic conductor; its resistance changes with temperature rather than staying constant.

How is a thermistor commonly used in devices?

A thermistor is used as a temperature sensor , commonly forming part of a thermostat that automatically regulates temperature or activates a device at a set temperature.

Thermistors are commonly used to regulate and monitor the temperature in environments where it must be carefully controlled, eg. ______ and beverage factories.

Thermistors are commonly used to regulate and monitor the temperature in environments where it must be carefully controlled, eg. food and beverage factories.

Name three devices that use a thermistor.

Any three from: ovens , refrigerators , fire alarms , digital thermometers , boilers .

Define light-dependent resistor (LDR) .

An LDR is a non-ohmic conductor whose resistance depends on the light intensity on it.

What happens to the resistance of an LDR as light intensity increases?

As light intensity increases , the resistance of an LDR decreases .

True or False? The resistance of an LDR stays the same regardless of light intensity.

False. The resistance of an LDR decreases as light intensity increases , and increases as light intensity decreases.

What is the main advantage of using an LDR in a circuit?

LDR circuits are automatic , so they do not need any human time or intervention to function correctly every day.

LDRs are found in lights that switch on when it gets dark, such as garden lights and ______ .

LDRs are found in lights that switch on when it gets dark, such as garden lights and street lights .

GCSEPhysicsAQAFlashcardsElectricityCurrent, Potential Difference & Resistance

Current, Potential Difference & Resistance (AQA GCSE Physics): Flashcards

Exam code: 8463

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Cards in this collection (71)

Define ammeter.
An ammeter is used to measure the current in a circuit. It is always connected in series with the component being measured.
Define voltmeter.
A voltmeter is used to measure the potential difference across a component. It is always connected in parallel with the component being measured.
Define fuse.
A fuse is a safety device that cuts off the flow of electricity to an appliance if the current becomes too large, by melting the fuse wire and breaking the circuit.
What does a diode do in a circuit?
A diode allows current to flow in one direction only. Current flows through it when it is in the forward bias position, and diodes are used to convert AC to DC current.
What three things does an electric circuit need to work effectively?
An energy source to provide potential difference, a closed path (complete circuit) for electrons to flow, and electrical components drawn with the correct circuit symbols.
As the temperature of a thermistor increases, its resistance ______.
As the temperature of a thermistor increases, its resistance decreases.
True or False?
Conventional current flows from the negative terminal to the positive terminal of a power supply.
False.
Conventional current always flows from the positive terminal to the negative terminal of the power supply.
How does the resistance of a light-dependent resistor (LDR) change as light intensity increases?
As light intensity increases, the resistance of an LDR decreases.
Define potential difference.
Potential difference is the energy transferred per unit charge flowing from one point to another. It is measured in volts (V).
Define electric current.
Electric current is the flow of electrical charge. It is the rate of flow of electrical charge, measured in amperes (A).
Write the equation linking potential difference (V), work done (W) and charge (Q).
$V = \frac{W}{Q}$
Write the equation linking charge (Q), current (I) and time (t).
$Q = I t$
The unit of charge is the ______, equal to the quantity of electricity conveyed in one second by a current of one ampere.
The unit of charge is the coulomb, equal to the quantity of electricity conveyed in one second by a current of one ampere.
In which direction do electrons flow through a circuit?
Electrons flow away from the negative terminal of a cell towards the positive terminal. This is opposite to the direction of conventional current.
True or False?
In a series circuit, the current is different at every point around the loop.
False.
In a closed-loop circuit, the current is the same value at any point, because the same number of electrons per second passes through every part of the circuit.
State three sources of potential difference.
A cell, a battery (multiple cells), and an electrical generator.
Define resistance.
Resistance is the opposition to current. The vibration of atoms in a wire slows down the flow of electrons; the higher the resistance, the lower the current.
Define the ohm.
The ohm (Ω) is the unit of resistance. One ohm is defined as one volt per ampere (1 V A⁻¹).
Write the equation linking potential difference (V), current (I) and resistance (R).
$V = I R$
The greater the resistance of a component, the ______ the current for a given potential difference.
The greater the resistance of a component, the lower the current for a given potential difference.
Calculate the potential difference across a resistor of resistance 15 Ω when a current of 0.2 A flows through it.
$V = I R = 0.2 \times 15 = 3 V$
True or False?
Good electrical conductors have a high resistance.
False.
Good conductors have a low resistance, while insulators have a high resistance.
The resistance of which two circuit components is assumed to be negligible in exam questions?
The resistance of wires and batteries is assumed to be negligible in exam questions.
How does increasing the resistance of a component affect the current through it, for a constant potential difference?
The current decreases as the resistance increases, for a given potential difference.
In the experiment investigating resistance of a wire, what is the independent variable?
The length of the resistance wire, L.
State two control variables in the experiment investigating resistance of a wire.
The potential difference of the power supply and the temperature of the wire.
Which equation is used to calculate resistance from the voltmeter and ammeter readings?
$R = \frac{V}{I}$
What is the relationship between the resistance of a wire and its length?
Resistance is directly proportional to the length of the wire, shown by a straight line graph through the origin with a positive correlation.
How does the total resistance of two resistors connected in series compare to the sum of their individual resistances?
It is equal to the sum of the two individual resistances, as the current flows through just one path through both resistors.
How does the total resistance of two resistors connected in parallel compare to the sum of their individual resistances?
It is less than the sum of the two individual resistances, as the current is split between the different paths.
To reduce systematic errors, only allow ______ currents to flow through the wire so its temperature stays constant.
To reduce systematic errors, only allow small currents to flow through the wire so its temperature stays constant.
True or False?
A zero error can occur if the first crocodile clip does not start at 0 on the ruler.
True.
The first crocodile clip connected to the circuit must start at 0 on the ruler, otherwise this causes a zero error in the length measurements.
Define fixed resistor.
A fixed resistor has a resistance that remains constant.
Define variable resistor.
A variable resistor can change the resistance through a circuit, which varies the amount of current flowing through it.
For fixed and variable resistors, once the resistance is set, it stays at this value no matter how the ______ changes.
For fixed and variable resistors, once the resistance is set, it stays at this value no matter how the current changes.
Name four components (other than fixed and variable resistors) whose resistance changes with the current through them.
Lamps, diodes (including LEDs), thermistors and LDRs (light-dependent resistors).
True or False?
Fixed resistors and variable resistors have the same circuit symbol.
False.
Fixed and variable resistors have different circuit symbols.
Define ohmic conductor.
An ohmic conductor obeys Ohm's Law. At constant temperature, its resistance is constant and its I–V graph is a straight line through the origin.
State Ohm's law.
The current through a conductor is directly proportional to the potential difference across it, at constant temperature.
Give three examples of ohmic conductors.
Fixed resistors, wires and heating elements.
Why does the resistance of a filament lamp increase as the current through it increases?
The increasing current raises the filament's temperature, causing the atoms in its metal lattice to vibrate more. This makes it harder for electrons to pass through, increasing resistance.
A diode allows current to flow in ______ direction only, called forward bias.
A diode allows current to flow in one direction only, called forward bias.
What happens to the current when a diode is in reverse bias?
In reverse bias, the diode has very high resistance, so no current flows.
True or False?
A filament lamp is an example of an ohmic conductor.
False.
A filament lamp is non-ohmic — its current and potential difference are not directly proportional.
Name four examples of non-linear circuit components.
Filament lamps, diodes and LEDs, LDRs and thermistors.
Define thermistor.
A thermistor is a non-ohmic conductor whose resistance depends on its temperature.
What happens to the resistance of a thermistor as its temperature increases?
As temperature increases, the resistance of a thermistor decreases.
True or False?
A thermistor is an ohmic conductor.
False.
A thermistor is a non-ohmic conductor; its resistance changes with temperature rather than staying constant.
How is a thermistor commonly used in devices?
A thermistor is used as a temperature sensor, commonly forming part of a thermostat that automatically regulates temperature or activates a device at a set temperature.
Thermistors are commonly used to regulate and monitor the temperature in environments where it must be carefully controlled, eg. ______ and beverage factories.
Thermistors are commonly used to regulate and monitor the temperature in environments where it must be carefully controlled, eg. food and beverage factories.
Name three devices that use a thermistor.
Any three from: ovens, refrigerators, fire alarms, digital thermometers, boilers.
Define light-dependent resistor (LDR).
An LDR is a non-ohmic conductor whose resistance depends on the light intensity on it.
What happens to the resistance of an LDR as light intensity increases?
As light intensity increases, the resistance of an LDR decreases.
True or False?
The resistance of an LDR stays the same regardless of light intensity.
False.
The resistance of an LDR decreases as light intensity increases, and increases as light intensity decreases.
What is the main advantage of using an LDR in a circuit?
LDR circuits are automatic, so they do not need any human time or intervention to function correctly every day.
LDRs are found in lights that switch on when it gets dark, such as garden lights and ______.
LDRs are found in lights that switch on when it gets dark, such as garden lights and street lights.
Name three devices or circuits that use an LDR.
Any three from: lights that switch on when it gets dark (eg. garden or street lights), alarm clocks, burglar alarm circuits, light intensity meters, security lights.
How should the ammeter and voltmeter be connected to a component to measure its resistance?
The ammeter is connected in series with the component and the voltmeter is connected in parallel with the component.
Why should a low power supply voltage be used when investigating the resistance of a thermistor or LDR?
A low voltage (below 15 V) is used, otherwise too high a current in the circuit would start to affect the resistance of the component.
How should the light intensity be increased when investigating the resistance of an LDR?
Starting in a dark room with the lamp turned off, the light intensity is slowly increased using a dimmer switch, recording the voltmeter and ammeter readings at each increase.
Why should you wait a few seconds before taking readings when investigating a thermistor or LDR?
To allow the thermistor or LDR time to react to the change in temperature or light intensity.
The resistance of a component is calculated using the equation R = ______.
The resistance of a component is calculated using the equation R = V / I.
True or False?
In the LDR and thermistor circuits, the lamp or heater should be touching the LDR or thermistor.
False.
The lamp and heater should be close to, but not touching, the LDR and thermistor respectively.
What are the independent and dependent variables in the I–V characteristics required practical?
The independent variable is the potential difference, V, across the component; the dependent variable is the current, I, through it.
Which three circuit elements are investigated in this required practical?
A fixed resistor, a filament lamp and a diode.
Define ohmic conductor.
An ohmic conductor produces a straight-line I–V graph, meaning it obeys Ohm's law: V = IR.
Why should the circuit be switched off between voltage readings?
To prevent heating of the component and wires, which could affect the resistance readings.
Why are the terminals of the power supply reversed during the experiment?
To take readings for negative voltage (and therefore negative current) as well as positive.
For each voltage, the current should be recorded from the ammeter ______ and the average calculated, to improve accuracy.
For each voltage, the current should be recorded from the ammeter three times and the average calculated, to improve accuracy.
True or False?
A curved I–V graph indicates that a component is an ohmic conductor.
False.
A curved I–V graph indicates a non-ohmic conductor, such as the filament lamp or diode.
What is the role of the variable resistor in this experiment?
It is used to change the potential difference (p.d.) across the component, particularly when using a battery or a fixed power-pack setting where the p.d. would otherwise stay constant.

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