Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BMAT > Physics - Electricity > Flashcards

Physics - Electricity Flashcards

1
Q

what is an electrostatic conductor

A

material that is able to disperse electrical current (electrons) easily

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is an electrostatic insulator

A

do not disperse electrical charge (electrons) easily

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what happens when two electrostatic insulators are rubbed together

A

there is a flow of charge from one insulator to another
insulator that loses electrons becomes positively charged
insulator that gains electrons becomes negatively charged

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

induction

A

place a neutral object next to charged object causes it to become charged
if one end of this newly charged object is momentarily earthed, the object becomes permanently charged

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what happens is a newly charged object is momentarily earthed

A

becomes permanently charged

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

example of static electricity in industry

A

spray paint
paint droplets have opposite charges to the object being painted meaning they are attracted to the object and less paint is wasted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

why can static electricity be dangerous

A

sparks can form upon spontaneous dissipation of electrical charge which can lead to a fire

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what can reduce the risk of a spark

A

earthing an object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the two ways current can be supplied

A

direct
alternating

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

direct current

A

current always supplied in same direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

examples of uses of direct current

A

batteries or cells supply

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

alternating current

A

current that repeatedly changes direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

examples of uses of alternating current

A

power stations output and the mains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is a waveform

A

current changes at certain regular frequency which produces a waveform

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the frequency of mains current in UK and Europe

A

50Hz
50 oscillations or 100 changes in direction per second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is current

A

flow of charged particles through an electrical conductor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what symbol represents current

A

I

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is current measured in

A

amperes (A)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

how to calculate current

A

current = charge / time

current = amperes (A)
charge = coulomb (C)
time = second (s)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

how to measure current

A

ammeter placed in series with components of series

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is potential difference (voltage)

A

work done to move charge between two points

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what symbol represents voltage

A

V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is voltage measured in

A

volts (V)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

how to calculate voltage

A

voltage = work done / charge

voltage = volts (V)
work done = joules (J)
charge = coulomb (C)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

how to measure voltage

A

voltmeter which is always placed in parallel with the component whose potential difference you are trying to measure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what is resistance

A

opposition to the flow of current (electrons) through a conductor

all conductors carry a certain resistance which is directly proportional to the length of the conductor and inversely proportional to the cross sectional area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what symbol represents resistance

A

R

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what units are used for resistance

A

ohms (Ω)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

how to calculate resistance

A

resistance = voltage / current

resistance = ohms (Ω)
voltage = volts (V)
current = amperes (A)

30
Q

what is 1 ampere

A

1 coulomb of charge flows through a conductor per second

31
Q

what is 1 volt

A

work done moving 1 coulomb of charge between two points

32
Q

what is 1 ohm

A

resistance of a conductor when a potential difference of 1 volt produces a current of 1 ampere

33
Q

voltage-current graphs are linked by which equation

A

voltage = current x resistance

34
Q

how is a voltage-current graph plotted

A

current on y axis
voltage on x axis

35
Q

what is an ohmic conductor

A

a fixed resistor maintains constant resistance with different currents flowing through it

36
Q

ohmic conductors
what is current and voltage relationship

A

directly proportional

37
Q

how to calculate resistance on voltage-current graph

A

1/gradient

38
Q

what are non-ohmic conductors

A

resistance alters with varying current flowing through them and varying potential differences across them

39
Q

non-ohmic conductors
what is current and voltage relationship

A

sigmoidal curve

40
Q

example of non-ohmic conductor

A

filament lamp

41
Q

why is filament lamp non-ohmic

A

as more current flows through filament lamp, it begins to heat up due to increased electron collisions

heat generated leads to an increased resistance through filament lamp as particles vibrate with greater amplitude, making it harder for the free electrons to flow through the conductor

this leads to a decrease in current

42
Q

thermistors

A

thermistors are components whose resistance is dependent on temperature

43
Q

example of thermistor

A

negative coefficient (NTC) thermistor’s resistance decreases as its temperature increases

44
Q

light dependent resistors

A

components whose resistance is dependent on light intensity incident on it

resistance of LDR decreases as light intensity increases

45
Q

ideal diodes

A

components that only allow current to flow in one direction which is shown by the arrowhead in the circuit symbol for the diode

46
Q

what can diodes require before current flows through them sometimes

A

forward junction potential

47
Q

what is a diode’s breakdown voltage

A

in the reverse direction

causes negative current to flow through them

48
Q

series circuit

A

components placed on one long continuous path and current flows through every component

49
Q

current in a series circuit

A

it is the same no matter where in the circuit it is measured from

50
Q

potential difference in a series circuit

A

equal to the sum of potential difference across each of the components that the series circuit contains

this is because the energy carried by each coulomb of charge must be shared as it travels through each component

VT = V1 + V2 + V3

51
Q

resistance in series circuit

A

sum of all components in a circuit

RT = R1 + R2 + R3

52
Q

how to calculate the voltage in a cell or battery in series

A

VT = RT x IT

53
Q

what is a parallel circuit

A

components are arranged in several ‘parallel’ branches
(can be in a series of series and parallel)

54
Q

potential difference in parallel circuit

A

same across each loop in a parallel circuit

due to the fact that the electrons entering each loop have the same amount of energy

the total voltage supplied by the cell is equal to the voltage across each of the loops in the parallel circuit

VT = V1 = V2 = V3

55
Q

current in parallel circuit

A

shared between branches in ratio of resistance od components in each branch

therefore, at a branch point the current will be equal to the sum of the currents going into each branch

IT = I1 + I2 + I3

56
Q

resistance in parallel circuit

A

reciprocal law

1/RT = 1/R1 + 1/R2 + 1/R3

dealing with circuits that consist of a combination of series and parallel resistors, use the reciprocal rule to calculate the total resistance of the parallel portion before adding the series resistances

57
Q

electrical power equation

A

power = energy / time

power in watts (W)
energy in joules (J)
time in seconds (s)

58
Q

transfer of electrical power equation
(using V and I)

A

power = voltage x current

power in watts (W)
voltage in volts (V)
current in amperes (A)

59
Q

transfer of electrical power equation
(using I and R)

A

power = current^2 x resistance

power in watts (W)
current in amperes (A)
resistance in ohms (Ω)

60
Q

transfer of electrical power equation
(using V and R)

A

power = voltage^2 / resistance

power in watts (W)
voltage in volts (V)
resistance in ohms (Ω)

61
Q

energy equation
(using V I and T)

A

energy = voltage x current x time

energy in joules (J)
voltage in volts (V)
current in amperes (A)
time in seconds (s)

62
Q

what do transformers do

A

devices that have the ability to alter voltage and current

63
Q

what do step up transformers do

A

increase voltage and decrease current

useful when transferring electricity from power stations to national grid in order to reduce energy losses

64
Q

what do step down transformers do

A

decrease voltage and increase current

more safe use in our homes and reduces risk of electric shocks

65
Q

what does a transformer consist of and why

A

primary coil wrapped around coil
when a current is allowed to flow through the primary coil, it creates a magnetic current which induces a current in a secondary coil

66
Q

current and voltage can then be altered by varying the ratio of turns in the primary and secondary coils

A

(v in secondary coil / v in primary coil)

(turns on secondary coil / turns on primary coil)

67
Q

power calculation using primary voltage and primary current

A

power = primary voltage x primary current

68
Q

power calculation using secondary voltage and secondary current

A

power = secondary voltage x secondary current

69
Q

generator effect

A

generation of a current by the movement of an electrical conductor relative to a magnetic field

also : keeping stationary conductor in a fluctuating magnetic field

70
Q

what does a generator consist of and why

A

wire rotating in a magnetic field

  • as it rotates each side of the coil moves through the magnetic field in two different directions withe each 360 degree rotation
  • wire simultaneously moving in opposite direction through the magnetic field, produces alternating current

BMAT (33 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions