P3

Question 1

What is charge and what types of charges are there?

Answer 1

Charge is a property of all matter and there are positive and negative charges

Question 2

In most bodies there are … resulting in the body …

Answer 2

an equal number of positive and negative charges / having zero net charge

Question 3

Describe the production of static electricity

Answer 3

When two insulators are rubbed together electrons are transferred from one insulator to another.

Question 4

Describe the production of sparking

Answer 4

Sparking is made by a flow of current or charge through the air

Question 5

Give an example of how charged objects exert forces of attraction and repulsion while not in contact

Answer 5

If you create an electric field and place another object in the field the objects will attract or repel

Question 6

Explain how transfer of electrons between objects can explain the phenomena of static electricity

Answer 6

One object ends up with extra electrons and the other with not enough electrons to cancel out the positive charge

Question 7

Explain the concept of an electric field and how it helps to explain the phenomena of static electricity

Answer 7

When an electric field is stronger the field lines are closer together

Question 8

What is current?

Answer 8

Current is the rate of flow of charge (electrons)

Question 9

What conditions are required for charge to flow?

Answer 9

A source of potential difference and a closed circuit

Question 10

In a single closed loop, what is the current value on a point in the loop?

Answer 10

the current is the same value on any point in a single closed loop

Question 11

How do you calculate charge?

Answer 11

Charge (C) = current (A) x time (s)

Question 12

What are the names of common circuit elements? (8)

Answer 12

cell, diode, LDR, thermistor, filament lamp, ammeter, voltmeter, resistor

Question 13

What does current (I) depend on and what are the units for these?

Answer 13

Current depends on resistance (R) and potential difference (V). Resistance is measured in ohms and potential difference is measured in volts

Question 14

Define potential difference

Answer 14

A difference in (electrical) potential produced by separation of charge

Question 15

What does a potential difference produce?

Answer 15

It produces an electric field which produces a force on charged particles in it

Question 16

How do we calculate energy transferred in electrical working?

Answer 16

energy transferred (J) = potential difference (V) x charge (C)

Question 17

What is the main difference between a series and parallel circuit?

Answer 17

A series circuit has a single loop while a parallel circuit can have more than one loop

Question 18

Draw a series and a parallel circuit

Answer 18

see p.g. 102/103

Question 19

Draw where you would place an ammeter, resistors and voltmeter in a series circuit

Answer 19

see p.g. 102/103

Question 20

Draw where you would place an ammeter, resistors and voltmeter in a parallel circuit

Answer 20

see p.g. 102/103

Question 21

What is the behaviour of current in a parallel circuit

Answer 21

The currents in the loops add up to the current near the battery

Question 22

What is the behaviour of current in a parallel circuit

Answer 22

The currents in the loops add up to the current near the battery

Question 23

How do you calculate current from V, I and R?

Answer 23

current (A) = potential difference (V) / resistance (Ω)

Question 24

For some resistors the value of R remains … but in others it can … as the …

Answer 24

constant / change / current changes

For some resistors the value of R remains … but in others it can … as the …

Question 25

For some resistors the value of R remains ... but in others it can ... as the ...

Answer 25

constant / change / current changes | For some resistors the value of R remains ... but in others it can ... as the ...

Question 26

What is a characteristic graph?

Answer 26

A graph of current against potential difference

Question 27

Draw a characteristic graph for a linear circuit element

Answer 27

see p.g. 106

Question 28

Draw a characteristic graph for a wire in a light bulb. Why is it like this?

Answer 28

see p.g. 107 | As the electrons in the wire collide with the ions in the wire, causing it to heat up.

Question 29

What is a diode?

Answer 29

A diode is a component that allows a current to only flow one way

Question 30

Draw a characteristic graph for a diode. Why is it like this?

Answer 30

see p.g. 107 | As in one direction there is no current but in the other the current increases really quickly

Question 31

What is a thermistor?

Answer 31

A circuit component with a resistance that depends on temperature A semiconductor

Question 32

Draw a characteristic graph for a thermistor. Why is it like this?

Answer 32

see p.g. 108 As the temperature increases, many electrons gain enough energy to escape from the atoms in the semiconductor, so the resistance falls

Question 33

What is a semiconductor?

Answer 33

A material that contains atoms with loosely bound electrons that can be released if energy is transferred to the material

Question 34

What is a light-dependent resistor (LDR)?

Answer 34

A resistor in which its resistance changes with light intensity

Question 35

Draw a characteristic graph for an LDR. Why is it like this?

Answer 35

see p.g. 109 It is like this because as light intensity increases, more electrons are released in the semiconductor and the resistance decreases

Question 36

If two resistors are in series what happens to the resistance and why?

Answer 36

The net resistance increases because the potential difference increases and the current decreases

Question 37

If two resistors are in parallel what happens to the resistance and why?

Answer 37

The net resistance decreases because the potential difference doesn't change and the current increases

Question 38

Series - if you know current and resistance you can ...

Answer 38

work out p.d. across the lamp using V = IR

Question 39

Series - if you know p.d. across lamp and p.d. across cell you can ...

Answer 39

work out p.d. across a variable resistor using V(VR) = V(cell) - V(lamp)

Question 40

Series - if you know p.d. across variable resistor and current you can ...

Answer 40

work out resistance of variable resistor using R = V/I

Question 41

Parallel - if you know p.d. across resistor and p.d. across lamp you can ...

Answer 41

work out current through resistor, using I = V/R

Question 42

Parallel - if you know current near battery you can ...

Answer 42

work out current through lamp using I(lamp) = I(battery) - I(resistor)

Question 43

Parallel - if you know p.d. across lamp and current through lamp you can ...

Answer 43

work out resistance of lamp, using R = V/I

Question 44

What are sensing circuits?

Answer 44

Sensing circuits are ones which contain a component with a resistance that changes with a change in environment (e.g. temp)

Question 45

How do you calculate electrical power?

Answer 45

power (W) = potential difference (V) x current (A)

Question 46

How do calculate energy transferred?

Answer 46

energy transferred (J, kWh) = power (W) x time (s)

Question 47

How is power related to current and resistance?

Answer 47

V = I x R P = V x I = I x R x I = I^2 x R P = I^2R