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Physics > P3 > Flashcards

P3 Flashcards

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1
Q

What is charge and what types of charges are there?

A

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

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2
Q

In most bodies there are … resulting in the body …

A

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

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3
Q

Describe the production of static electricity

A

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

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4
Q

Describe the production of sparking

A

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

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5
Q

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

A

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

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6
Q

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

A

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

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7
Q

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

A

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

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8
Q

What is current?

A

Current is the rate of flow of charge (electrons)

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9
Q

What conditions are required for charge to flow?

A

A source of potential difference and a closed circuit

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10
Q

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

A

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

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11
Q

How do you calculate charge?

A

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

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12
Q

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

A

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

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13
Q

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

A

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

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14
Q

Define potential difference

A

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

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15
Q

What does a potential difference produce?

A

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

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16
Q

How do we calculate energy transferred in electrical working?

A

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

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17
Q

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

A

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

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18
Q

Draw a series and a parallel circuit

A

see p.g. 102/103

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19
Q

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

A

see p.g. 102/103

20
Q

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

A

see p.g. 102/103

21
Q

What is the behaviour of current in a parallel circuit

A

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

22
Q

What is the behaviour of current in a parallel circuit

A

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

23
Q

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

A

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

24
Q

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

A

constant / change / current changes

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

25
Q

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

A

constant / change / current changes

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

26
Q

What is a characteristic graph?

A

A graph of current against potential difference

27
Q

Draw a characteristic graph for a linear circuit element

A

see p.g. 106

28
Q

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

A

see p.g. 107

As the electrons in the wire collide with the ions in the wire, causing it to heat up.

29
Q

What is a diode?

A

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

30
Q

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

A

see p.g. 107

As in one direction there is no current but in the other the current increases really quickly

31
Q

What is a thermistor?

A

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

32
Q

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

A

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

33
Q

What is a semiconductor?

A

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

34
Q

What is a light-dependent resistor (LDR)?

A

A resistor in which its resistance changes with light intensity

35
Q

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

A

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

36
Q

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

A

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

37
Q

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

A

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

38
Q

Series - if you know current and resistance you can …

A

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

39
Q

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

A

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

40
Q

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

A

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

41
Q

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

A

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

42
Q

Parallel - if you know current near battery you can …

A

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

43
Q

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

A

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

44
Q

What are sensing circuits?

A

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

45
Q

How do you calculate electrical power?

A

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

46
Q

How do calculate energy transferred?

A

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

47
Q

How is power related to current and resistance?

A

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

P = I^2R

Physics (6 decks)

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