Current Electricity Flashcards
The flow of current through a conductor is due to
Free electrons
The specific resistance of wire depends upon
material
A wire is stretched to double its length, its resistance will be
Four times
the unit of specific resistance is
Ohm meter
Is copper wire an Ohmic resistance
Yes
In Semiconductor on raising temp. what happens to its resistance
decreases
the conductance of super conductor is
infinite
the e.m.f. of a cell depends upon
nature of electrolyte and electrodes
Kirchoff’s first law is in accordance with
Law of conservation of charge
the internal resistance of a cell can be decreased by:
decreasing the distance between electrodes.
THE PROPERTY WHICH DIFFERENTIATES BETWEEN 2 DIFFERENT KINDS OF CHARGES IS CALLED
POLARITY OF CHARGE
WHY GOLD LEAF ELECTROSCOPE IS USED ?
TO DETECT CHARGE ON BODY
DEFINE CONDUCTOR
THOSE WHICH ALLOWS ELECTRICITY TO PASS THRIUGH THEM EASILY ARE CALLED CONDUCTORS
DEFINE INSULATORS
THOSE MATERIALS WHO DONT LET ELECTRICITY PASS THROUGH THEM ARE INSULATORS
DEFINE EARTHING OR GROUNDING
THE PROCESS OF SHARING CHARGE TO EARTH IS CALLED EARTHING GROUNDING
IN INDUCTION CHARGING SPHERES ARE
EQUALLY AND OPPOSTIVELY CHARGED
NO . OF ELECTRONS IN 1COULONB CHARGE
6X10^18
A CUBIC PIECE OF COPPER OF SIDE 1CM CONTAINS ABOUT— ELECTRONS
2.5X10^24
COULOMB LAW
I DONT THINK I NEED TO WRITE THIS
VALUE OF K AND UNIT
9X13^9
NM^2/C^2
VALUE OF PERMITTIVITY OF FREE SPACE
E0 = 8.854X10^-12 N-1 M-2
ELECTRIC FILED
Qq/
4⊓E0 r^2
SI UNIT OF ELECTRIC FEILD
N/C
IT IS A VECTOR QUANTITY
DIRECTION OF ELECTRIC FEILD
FOR+VE RADAILLY OUTWARDS
FOR-VE RADAILLY INWARDS
DIRECTION OF ELECTRIC FEILD LINES
START FROM +VE AND END AT -VE
FIELD OF ELECTRIC DIPOLE
FOR POINTS ON AXIS
-VE = E =-QP/4⨅E0(R+A)2
+VE= E = QP/4⨅E0(R-A)2
FOR POINTS ON EQUITORIAL PLANE
E=-P/4⨅E0R3
ELECTRIC FLUX
∆∅=E∆SCOS⩉
SI UNIT OF ELECTRIC FLUX
N/CM2
P=
QX2A
DEFINE ELECTRIC DIPOLE
AN ELECTRIC DIPOLE IS A PAIR OF EQUAL AND OPPOSITE POINT CHARGES Q AND -Q SEPARTED BY 2a
FIELD DUE TO UNIFORMLY CHARGED INFINITE PLANE SHEET
E = σ /2 E0
TORQUE CU OF UNIFORE ELECTRIC FELID
ɽ=q E 2aSIN⩉=pxE
FEILD DUE TO UNIFORMLY CHARGED THIN SPHERICAL SHELL
OUTSIDE – E = Q/4⨅E0R2
INSIDE – E = 0
FEILD DUE TO INFINITELY LONG STRAIGHT WIRE
E = ʎ/2⨅E0r
DEFINE SURFACE CHARGE DENSITY
Suppose q is the charge and a is the area of the surface over which it flows, then the formula of surface charge density is σ = q/A, and the S.I. unit of surface charge density is coulombs per square meter (cm−2).
DEFINE LINEAR CHARGE DENSITY
Per unit length i.e. linear charge density, where q is the charge and is the length over which it is distributed. The SI unit will be Coulomb (m ^ {-1}).
FORMULA –ʎ=∆Q/∆L
DEFINE VOLUME CHARGE DENSITY
Per unit volume i.e. volume charge density, where q is the charge and V is the volume of distribution. The SI unit is Coulomb (m ^ {-3}).
FORMULA – P=∆Q/∆V
DEFINE GAUSS LAW
Gauss’s law for electricity states that the electric flux Φ across any closed surface is proportional to the net electric charge q enclosed by the surface; that is, Φ = q/ε0, where ε0 is the electric permittivity of free space
IMPORTANT PROPERTIES OF FEILD LINES ARE
1] FIELD LINES ARE CONTINOUS CUVERS WITHOUT ANY BREAKAGE
2] TWO FIELD LINES NEVER INTERSECT E/O
3] THEY START FROM +VE TO-VE
4] THEY DO NOT FORM CLOSED LOOP
DEFINE ELECTRIC CURRENT
Electric Current is the rate of flow of electrons in a conductor. The SI Unit of electric current is the Ampere.
DEFINE INOSPHERE
IN NATURE FREE CHARGED PARTICLES DO EXIST LIKE IN UPPER STRATA OF ATMOSPHERE CALLED INOSPHERE
WRITE OHM LAW
V = I R
WRITE FORMULA OF RESISTANCE
R = P L / A
P IS RESISTIVTY
FORMULA OD CHARGE DENSITY
J = I /A
J = σE
σ IS CONDUCTIVITY
RELATION B/W CONDUCTIVITY AND RESISTIVITY
σ= 1/P
DEFINE DRIFT VELOCITY
When electrons are subjected to an electric field they do move randomly, but they slowly drift in one direction, in the direction of the electric field applied. The net velocity at which these electrons drift is known as drift velocity.
FORMULA OF DRIFT VELOCITY
I = n v A Q
DEFINE MOBILITY
The drift velocity of an electron for a unit electric field is known as the mobility of the electron
⋃= Vd /E
RESISTOR COLOUR CODES
READ FROM NCERT
TEMPTURE DEPANDANCE OF RESISTIVITY
ρT= ρ0 [1 + a(T–T0)]
FORMULA OF ELECTRICAL ENERGY
dK = I Vdt
electrical power
P = I 2 R = V 2/R = I V
RESISTANCE IN PARALLEL
Req=1/R1+1/R2….
RESISTANCE IN SERIES
Req=R1+R2….
DEFINE ELECTROMOTIVE FORCE EMF
V+ – (–V–) = [V+]+ V–
. This difference is called the
electromotive force (emf) of the cell and is denoted by e.
DEFINE INTERNA REISTANCE
The electrolyte through which a current flows has a finite
resistance r, called the internal resistance
V=
= e – I r
The maximum current that can be drawn from a cell is for R = 0
Imax = e/r
REVISE KHRICOOF LAW WHEATSTONE BRIDGE
Junction rule: At any junction, the sum of the currents entering
the junction is equal to the sum of currents leaving the junction
Loop rule: The algebraic sum of changes in
potential around any closed loop involving
resistors and cells in the loop is zero
CONDITON FOR BALANCE WHEATSTON BRIGDE
R1/ = R3/
R2 = R4
STUDY METER BRIDGE AND POTENTIOMETER
