Electricity

Question 1

Define the term ‘current’

Answer 1

Current is the rate of flow of charge.

Current flow has a direction and is defined as the flow of positive charges.

Question 2

Define the term ‘charge’

Answer 2

Charge is a fundamental property of some types of particles, such as protons and electrons.

Charge is measured in coulombs (C).

Question 3

How should a measurement of ‘exactly 85 cm’ be recorded?

Answer 3

0.850 m

Question 4

What is one advantage of using a diffraction grating over a double-slit arrangement?

Answer 4

A diffraction grating produces sharper fringes leading to more accurate measurements.

Question 5

What is the angle to the normal made by the maximum in degrees [°]?

Answer 5

𝜽

Question 6

What term describes the ‘rate of flow of charge’?

Answer 6

Current

Question 7

What happens at a junction in a circuit?

Answer 7

Charge carriers split up or combine.

Question 8

What is the unit of charge?

Answer 8

Coulombs (C)

Question 9

The size of the charge on an electron is: (-) _______ C.

Answer 9

1.60 x 10^-19

Question 10

How is one coulomb defined in terms of current?

Answer 10

One coulomb (C) is defined as the amount of charge that passes a point in 1 second when the current is 1 ampere.

Question 11

What is the conventional current direction?

Answer 11

The direction of flow of positive charges.

Question 12

What is drift velocity?

Answer 12

The average velocity at which charge carriers move through a conductor.

Question 13

Potential difference is defined as _______.

Answer 13

the work done per unit charge.

Question 14

What is another term for energy transferred?

Answer 14

Work done

Question 15

What is the relationship between potential difference (Pd), current, and power?

Answer 15

Pd = work done / charge and power = Pd x current.

Question 16

Power is measured in _______.

Answer 16

watts (W)

Question 17

What does Ohm’s law state?

Answer 17

The current through an ohmic conductor is directly proportional to the potential difference across it, provided temperature remains constant.

Question 18

Resistance is a measure of how _______.

Answer 18

difficult it is to get a current to pass through a substance.

Question 19

A component has a resistance of 1 Ω if a potential difference of 1 V makes a current of _______ flow through it.

Answer 19

1 A

Question 20

What is the formula for resistance?

Answer 20

Resistance (R) = Voltage (V) / Current (I)

Question 21

When energy is transferred to the charge, what happens?

Answer 21

It is ‘raised’ through a potential and energy is transferred to the charge as electrical potential energy.

Question 22

What is the average output power of a battery if it maintains a potential difference of 5.0 V and the average current is 2.0 A?

Answer 22

Power = Voltage x Current = 5.0 V x 2.0 A

Question 23

True or False: Current is the same across components connected in series.

Answer 23

True

Question 24

What is the formula relating power, voltage, and current?

Answer 24

Power (P) = Voltage (V) x Current (I)

Question 25

What is the potential difference across a component when 1 joule of energy is transferred moving 1 coulomb of charge?

Answer 25

1 volt (1 V = 1 J/C)

Question 26

What is resistance?

Answer 26

Resistance is a measure of how difficult it is to get a current to pass through a substance.

Question 27

What is the resistance of a component if a potential difference of 1 V makes a current of 1 A flow through it?

Answer 27

1 Ω

Question 28

According to Ohm’s law, what is the relationship between current and potential difference in an ohmic conductor?

Answer 28

The current is directly proportional to the potential difference across it.

Question 29

List typical ohmic conductors.

Answer 29

* Aluminium * Iron * Titanium * Copper * Silver * Gold

Question 30

How does resistance change with the length of a conductor?

Answer 30

Resistance increases with length.

Question 31

How does resistance change with the diameter or cross-sectional area of a conductor?

Answer 31

Resistance decreases with diameter or cross-sectional area.

Question 32

What is resistivity?

Answer 32

Resistivity of a material is defined as the resistance of a 1 m length with 1 m² cross-sectional area.

Question 33

What is the unit of resistivity in terms of SI base units?

Answer 33

Ω m = W A⁻² m = J s⁻¹ A⁻² m = kg m s⁻² m s⁻¹ A⁻² m = kg m³ s⁻³ A⁻²

Question 34

What happens to resistance if the length of a wire is tripled?

Answer 34

Resistance will also triple.

Question 35

What happens to resistance if the cross-sectional area of a wire is halved?

Answer 35

Resistance will double.

Question 36

What is the effect of quadrupling the diameter of a wire on its resistance?

Answer 36

Resistance will change by a factor of 1/16.

Question 37

What is the effect of doubling both the diameter and length of a wire on its resistance?

Answer 37

Overall, the resistance will halve.

Question 38

What is a negative temperature coefficient (ntc) thermistor?

Answer 38

A thermistor whose resistance decreases as the temperature increases.

Question 39

What causes the resistance of a thermistor to decrease when warmed?

Answer 39

More electrons gain enough energy to escape from their atoms, increasing charge carriers.

Question 40

What is superconductivity?

Answer 40

A property of certain materials which have zero resistivity at and below a critical temperature.

Question 41

What are some uses of superconductors?

Answer 41

* Power cables that transmit electricity without any power loss * Really strong electromagnets

Question 42

What is the effect of cooling materials below their critical temperature?

Answer 42

Their resistivity disappears entirely and they become superconductors.

Question 43

What is the definition of potential difference?

Answer 43

The work done per unit charge between two points.

Question 44

What is the primary application of thermistors in the AQA A-level Physics specification?

Answer 44

Temperature sensors and resistance–temperature graphs.

Question 45

What is the resistivity of copper at 25 °C?

Answer 45

1.72 x 10⁻⁸ Ω m.

Question 46

What is the relationship between resistance and resistivity?

Answer 46

Resistance is a property of an object, while resistivity is a property of a material.

Question 47

True or False: Superconductors can operate at temperatures above 10 K.

Answer 47

False

Question 48

What is the critical temperature for most normal conductors?

Answer 48

Below 10 K (-263 °C).

Question 49

Fill in the blank: The lower the resistivity of a material, the _______.

Answer 49

better it is at conducting electricity.

Question 50

What characteristics of an electrical component can be determined using a specific circuit?

Answer 50

The characteristics of a component can be investigated using a circuit designed for that purpose. ## Footnote This includes measuring resistance, current, and voltage.

Question 51

What is the assumed resistance of an ideal voltmeter?

Answer 51

Infinite resistance. ## Footnote This ensures no current flows through it.

Question 52

What is the assumed resistance of an ideal ammeter?

Answer 52

No resistance. ## Footnote This ensures there is no potential difference across it.

Question 53

What is the term used to describe voltmeters and ammeters that have the most suitable resistance for their function?

Answer 53

Ideal.

Question 54

What type of component is a filament lamp classified as?

Answer 54

Non-ohmic component.

Question 55

How does increasing the potential difference across a filament lamp affect its temperature?

Answer 55

It raises the temperature.

Question 56

What happens to the resistance of a hot filament in a lamp?

Answer 56

The resistance becomes greater.

Question 57

How does the current behave in relation to the voltage in a filament lamp?

Answer 57

The current does not increase in proportion to the voltage.

Question 58

How do semiconductors compare to metals in terms of conductivity?

Answer 58

Semiconductors are not as good as metals at conducting electricity.

Question 59

What can cause the conductivity of semiconductors to increase?

Answer 59

Changes to the physical conditions of semiconductors.

Question 60

Name three common semiconductor components.

Answer 60

* Thermistors * Diodes * LDRs

Question 61

What does the triangle in the diode circuit symbol indicate?

Answer 61

The direction in which it will let current flow.

Question 62

What is the forward bias in relation to diodes?

Answer 62

The direction in which the current is allowed to flow.

Question 63

What is the typical threshold voltage required for most diodes to conduct?

Answer 63

Around 0.6 V.

Question 64

In reverse bias, is the resistance of a diode high or low?

Answer 64

Very high.

Question 65

What happens to the current flowing through a diode in reverse bias?

Answer 65

It becomes incredibly small.

Question 66

What is the significance of a full risk assessment in an investigation?

Answer 66

It identifies potential hazards and ensures safety.

Question 67

How can the accuracy of an investigation be increased?

Answer 67

By applying theoretical knowledge and controlling variables.

Question 68

What should be included in the evaluation section of a practical write-up?

Answer 68

Calculating relevant experimental values and uncertainties.

Question 69

What is the importance of citing sources in a practical write-up?

Answer 69

To provide evidence and credibility to the research.

Question 70

What is a common mistake to avoid when referencing a webpage?

Answer 70

Failing to include the accessed date.

Question 71

Fill in the blank: The process of determining the resistivity of a wire involves using a _______.

Answer 71

[Micrometer Screw Gauge, Ammeter and Voltmeter].