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PHYSICS > CURRENT ELECTRICITY > Flashcards

CURRENT ELECTRICITY Flashcards

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1
Q

The motion of free electrons inside conductor is

A

random motion

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2
Q

what is drift velocity?

A

the uniform velocity gained by free electrons of conductor when it is attached with the battery of certain voltages

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3
Q

the value of random velocity of electrons is

A

10^+5 m/s

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4
Q

the value of drift velocity is

A

10^-5 m/s

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5
Q

the angle between drift velocity and electric intensity is

A

180°

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6
Q

the formula for drift velocity is

A

Vd = △V/neρL
OR
Vd = I/neA

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6
Q

what is electric current?

A

the rate of flow of charge to any cross-section of wire

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6
Q

formula for current

A

I = △Q/△t
OR
I = ne/△t

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7
Q

unit for current

A

ampere = coulomb / second

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8
Q

how many electrons per second constitute a current of 1 ampere?

A

6.25 x 10^18 e

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8
Q

state ohms law

A

current flowing through a conductor is directly proportional to the potential difference applied across its ends, provided that the physical state of the conductor remains same

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9
Q

the proportionality constant for ohm’s law is

A

1/R

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10
Q

write formula for ohm’s law

A

I = 1/R x V
V= IR

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11
Q

formula for resistance

A

R = V/ I

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12
Q

unit for resistance

A

ohm = volt / ampere

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13
Q

resistance depends upon

A

resistivity (ρ)
temperature
nature
length
area

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14
Q

base units of ohm are

A

kg m2 / sec3 A2

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15
Q

the slope for VI graph gives

A

R

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16
Q

the area under VI graph gives

A

Pave
average power

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17
Q

the graph between V and I is

A

straight line originating from origin

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18
Q

for a graph of VI where 4 lines are originating from axis, where a is closer to x-axis and d is closer to y-axis, what is the decreasing order of resistances?

A

Rd > Rc > Rb > Ra

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19
Q

a graph is drawn between V at x-axis and I at y-axis. four straight lines are originating from origin, with line ‘a’ being close to x-axis and line d being close to y-axis, what is the decreasing order of resistances?

A

Ra > Rb > Rc > Rd

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20
Q

a VI graph is drawn, with straight lines A and B originating from origin. line A is at 30° with x-axis and line B is at 30° from y-axis. what is the ratio of resistance of A to B?

A

3 : 1

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21
Q

for series combination of resistances, what is Req?

A

Req = R1 + R2 + R3

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22
Q

for series combination of resistors, which is same: current or voltage?

A

current

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23
Q

for series combination of resistors, the Req is _________ that any individual resistances.

A

greater

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24
Q

what will be Req for series combination of resistors, if all resistances are same?

A

Req = nR

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25
Q

for parallel combination of resistor, the equivalent resistance will be

A

1/Req = 1/R1 + 1/R2 + 1/R3

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26
Q

for parallel combination of resistors, which is same, current or voltage?

A

voltage

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27
Q

the equivalent resistance for parallel combination of resistors is __________ than any individual resistance.

A

smaller

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28
Q

the equivalent resistance for parallel combination of resistors if all the resistances are equal is

A

Req = R/n

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29
Q

formulas for power

A

P = W/t
OR
P = VI
OR
P = I^2 R (for series)
OR
P = V^2/R (for parallel)

29
Q

what is the manufacturing formula for bulb?

A

P = V^2/R

30
Q

power is _________ proportional to area of filament

A

directly

30
Q

what is power?

A

the rate of dissipation of electrical energy

31
Q

the resistance of a bulb is _______ proportional to its power

A

inversely

32
Q

1 unit of electricity is equal to how many kWh

A

1

32
Q

power is ________ proportional to the brightness for series circuit

A

inversely

32
Q

the bulb with highest power has ______ filament

A

thickest

33
Q

power is _____ proportional to brightness for parallel circuit

A

directly

34
Q

define electromotive force.

A

the work done on unit positive charge by the cell or battery is called electromotive force.

35
Q

the terminal voltage is always ______ than emf

A

less

36
Q

formula for emf if work and charge is given would be

A

emf = W/Q

36
Q

the SI unit for emf is

A

volt

37
Q

emf if terminal voltage, current and resistance is given would be

A

emf = V + Ir

38
Q

formula for emf for closed circuit would be

A

emf = V + Ir

38
Q

emf for open circuit is

A

V (terminal voltage)

39
Q

formula for emf of charging circuit would be

A

emf = V - Ir

40
Q

emf for short circuit would be

A

Ir

41
Q

emf for closed circuit will be _______ than terminal voltage

A

greater

42
Q

emf for open circuit will be ______ than terminal voltage

A

less

43
Q

Power output formula is

A

e^2 R / (R - r)^2 + 4rR

44
Q

maximum power output will be

A

e^2/4r

45
Q

Kirchhoff’s first rule can also be written as

A

sum of currents flowing towards a point is equal to the sum of currents flowing away from that point

45
Q

state Kirchhoff’s first rule

A

sum of all currents flowing in a closed loop is equal to 0

46
Q

mathematical representation of Kirchhoff’s first rule

A

Σ I = 0

47
Q

Kirchhoff’s first rule is another form of

A

law of conservation of energy

48
Q

state Kirchhoff’s 2nd rule

A

sum of all potential changes in a closed loop is always equal to 0

48
Q

Kirchhoff’s first rule is also known as

A

current rule, point rule or junction rule

49
Q

mathematical form of Kirchhoff’s 2nd rule

A

Σ V = 0

50
Q

Kirchhoff’s 2nd rule can also be written as

A

energy gained is equal to energy lost

51
Q

Kirchhoff’s 2nd rule is also known as

A

voltage rule or loop rule

51
Q

Kirchhoff’s 2nd rule is another form of

A

law of conservation of energy

52
Q

resistance is ______ proportional to length

A

directly

53
Q

resistance is ___________ proportional to area

A

inversely

54
Q

proportionality constant for R ∝ l/A is

A

ρ

55
Q

ρ is called

A

resistivity of conductor

56
Q

ρ depends on

A

nature of conductor and temperature of conductor

57
Q

what is affected by bending, compressing, stretching and cutting; resistance of resistivity?

A

resistance

58
Q

shortcut to find resistance of a conductor if it is stretched will be

A

n^2 R

59
Q

shortcut to find resistance of conductor if it stretched will be

A

R / n^2

60
Q

write 3 formula for resistance

A

R = ρ L/A
OR
R = 4ρL/ π D^2
OR
R = ρL/π r^2

60
Q

the reciprocal of resistance is called

A

conductance

60
Q

formula for conductance is

A

1/R

61
Q

unit of conductance is

A

mho, 1/ohm,

62
Q

the reciprocal of resistivity will be

A

conductivity

63
Q

formula for temperature coefficient would be

A

α = Rt - Rnot / Rnot △T

64
Q

α is positive for

A

conductors

65
Q

α is negative for

A

semi-conductors

PHYSICS (6 decks)

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