AQA Combine Physics 6.2

Question 1

Describe an I-V graph for a diode

Answer 1

Current will only flow in one direction (there is a very high resistance in the other direction)

Question 2

Describe an I-V graph for an ohmic resistor (e.g. resistor at a constant temperature)

Answer 2

Current (at constant temperature) is directly proportional to potential difference

Question 3

What happebs to the resistance of an ohmic conductor (such as a wire) when the current changes?

Answer 3

The resistance of ohmic conductors doesn’t change with current

Question 4

For a given potential difference, what happens to the current when the resistance increases?

Answer 4

The current gets smaller

Question 5

In a single closed loop, what value would the current have at any point?

Answer 5

The same value

Question 6

What is electrical current and what determines the size of the current?

Answer 6

The flow of electrical charge, determined by the rate of flow

Question 7

What are the two ways of joining an electrical component?

Answer 7

In series or in parallell=

Question 8

Where are LDRs commonly found?

Answer 8

LDRs are used as automatic night lights/burglar detectors

Question 9

Where are thermistors commonly found?

Answer 9

Car engine temperature sensors/electronic thermostats

Question 10

Describe direct current supplies

Answer 10

Current that is always flowing in the same direction (created by a direct voltage)

Question 11

What type of electricity supply is mains?

Answer 11

Alternating current (AC)

Question 12

How can the total current through a parallel circuit be calculated?

Answer 12

It is the sum of the currents through the separate components

Question 13

What is the equation for Rtotal?

Answer 13

Rtotal = R1 + R2

Question 14

What equation links power, current and potential difference?

Answer 14

Power = current x potential difference
P = I V

Question 15

What equation links power, current and resistance?

Answer 15

Power = current 2 x resistance
P = I2 R

Question 16

What is the function of the Earth wire (green/yellow)?

Answer 16

Acts as a safety device, stopping the appliance casing from becoming live (OV)

Question 17

What is the function of the live wire (brown)?

Answer 17

Provides the alternating potential difference (230V)

Question 18

Describe the characteristics of the UK mains supply

Answer 18

230V AC with a frequency of 50Hz

Question 19

How are step-up transformers used within the National Grid?

Answer 19

Step-up transformers increase the potential difference of the National Grid to 400,00V

Question 20

What does the National Grid comprise of?

Answer 20

A system of cables and transformers linking power stations to consumers

Question 21

What effects of the power of a circuit?

Answer 21

• The potential difference and current which runs through it

- The energy transferred over a given time

Question 22

What is ‘done’ when change flows in a circuit?

Answer 22

Work (done)

Question 23

How can the gravitational potential energy of an object raised above the ground be calculated?

Answer 23

Gravitational Potential Energy = mass x gravitational field strength x height
Ep = m g h

Question 24

What is a three-core cable?

Answer 24

Three wires (core of copper) with a brown (live wire), blue (neutral wire) and green/yellow (Earth wire)

Question 25

How is the National Grid made as a efficient as possible?

Answer 25

A high potential difference and a low current which, for a given power, decreases energy lost by heating (the wires / surroundings)

Question 26

In the UK, how is electricity distributed?

Answer 26

Via the National Grid

Question 27

How can the live wire cause an electric shock?

Answer 27

Touching a live wire (230V) puts a large potential difference across your body (OV) which can shock / kill

Question 28

What is the function of the neutral wire (blue)

Answer 28

Completes the circuit carrying current away (OV)

Question 29

In a parallel circuit what is the potential differences across each component like?

Answer 29

It is the same

Question 30

What would the total resistance of two resistors be?

Answer 30

Less than the resistance of the smallest individual resistor

Question 31

What type of electricity supply is a battery?

Answer 31

Direct current (DC)

Question 32

What happens to the resistance of a LDR as light increases?

Answer 32

As light increases a LDR's resistance decreases

Question 33

How are LDRs and thermistors used in sensing circuits?

Answer 33

Sensing circuits can be used to turn on / increase the power to components depending on conditions

Question 34

In a series circuit, what is the current like through all components?

Answer 34

The same

Question 35

What happens to the resistance of a diode or filament lamp when current changes?

Answer 35

Resistance increases with temperature, such as the current increases the resistance increases

Question 36

Describe an I-V graph for a filament lamp

Answer 36

As the current increases the temperature of the filament lamp increases meaning less current can flow per unit potential diffrence

Question 37

For electrical charge to flow through a closed circuit what must be included?

Answer 37

A source of potential difference

Question 38

What is the equation for charge flow?

Answer 38

Charge flow = current x time | Q = I t

Question 39

How are the step-down transformers used within the National Grid?

Answer 39

Step-down transformers bring the 400,000V of the National Grid down to 230V for domestic use

Question 40

What determines how much energy an appliance transfers?

Answer 40

How long the appliance is on for and the power of the appliance

Question 41

Describe alternating current supplies

Answer 41

Current which constantly changes direction

Question 42

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

Answer 42

As temperature increases a thermistor's resistance decreases

Question 43

How can the total resistance of two components in a series circuit be worked out?

Answer 43

The total resistance of the components in a series circuit is the sum of all of them

Question 44

What affects the current through a given component?

Answer 44

The resistance of the component and the potential difference across it

Question 45

How is the total potential difference distributed between the components in a series circuit?

Answer 45

It is shared

Question 46

What equation links energy transferred, power and time?

Answer 46

Energy transferred = power x time | E = P t

Question 47

What equation links energy transferred, charge flow and potential difference?

Answer 47

Energy transferred = charge flow x potential difference | E = Q V

Question 48

What equation links potential difference, current and voltage?

Answer 48

Potential difference = current x resistance | V = I R