Electric Current PHYSICS MODULE 3 Flashcards
The electric current is due to the flow of
a. Positive Charge only
b. Negative charge only
c. Both positive and negative charge
d. Neutral particles only
c. Both positive and negative charge
The electric current in a metallic conductor is due to the flow of
a. Electrons only
b. Electrons and positive only
c. Positive ions only
d. Neutral atoms only
a. Electrons only
The electric current in a liquid is due to the flow of
a. Electrons only
b.positive ions only
c. Negative and positive ions
d. Electrons and positive ions
c. negative and positive ions
The electric current in a discharge tube containing a gas is due to
a.Electrons only
b.positive ions only
c. negative and positive ions
d.electrons and positive ions
a.Electrons Only
Electric current is a
a. scalar quantity
b. vector quantity
c.sometimes scalar and sometimes vector
d. number only
a. scalar quantity
Which one is correct?
a. flow of charge is current
b.rate of flow of charge is called current
c.rate of doing work is
d. current rate of current is current.
b. rate a flow of charge is called current
What is the SI unit of electric current ?
a.A
b.N
c.Z
d.Up
a.A
If q=t²+4t+5,find I inst at t=3sec
a.10A
b.7A
c.8A
d.0A
a.10A
A 10⁹ electrons pass through a cross section of a conductor in 10-³ sec what is the current in Ampere?
a.1.6x10-⁷A
b.1.77x10⁷A
c.22.x10-⁵A
d.not possible
a.1.6x10-⁷A
If P=t²+1,then find q flow through a cross section between 0 to 3 sec.Also find the no.of e- that flows in this time.
a.12C,7.5x10-⁹C
b.14,7x10-¹⁹C
c.14C,12C
d.none
a.12C,7.5x10-⁹C
The drift velocity of electrons is of the order of
a.1m/s
b.10-⁴m/s
c.10⁶m/s
d.10-⁹m/s
b.10-⁴m/s
The thermal speed(random motion)of electrons is of the order is
a.1m/s
b.10-³m/s
c.10⁵m/s
d.3x10⁸m/s
c.10⁵m/s
In metal conductors of electricity is due to
a.free electrons
b.bound electrons
c.Ions
d.Atoms
a.free electrons
What is the average velocity of electron when no potential is given to a conductive
a.0
b.1
c.2
d.1.5
a.0
Formula of drift velocity
Vd=I/neA
Formula of current density
J=I/A
Which one is vector quantity
a.Current
b.Current Density
c.Charge
d.Mass
b.Current Density
A wire has non-uniform cross section.It carries a current i.Then the drift velocity of electron :-
A •o————0 •B
a.remains constant from A to B
b.Decreases on moving from A to B
c.increases on moving from A to B
d.first increase then become comstant
b.decreases on moving from A to B
A steady current is passing through a linear conductor of non- uniform cross section. The current density in the conductor is
a.Independence of cross section b.directly proportional to area of cross section
c.Inversely proportional to area of cross section
d. inversely proportional to the square root of area of cross section
c.inversely propertional to area of cross section
My mistake question
A steady current passing through a linear conductor of non uniform cross section .The current in the conductor is :-
a.independent of area of cross section
b.directly proportional to the length of conductor
c.directly proportional to area of cross section
d. inversely proportional to length of the conductor
a.independent of area
Kinaki current density haina current cha
Formula of resistance
R=V/I
V: potential difference
I: electric current
Unit of resistance
Ohm
Ohms law formula
V=IR
Resistance of conductor is ________for ohmic conductor
Constant
Ohmic conductor example
Silver
Copper wire
Nichrome wire
Gold
Non ohmic conductor
Diodes
Semi conductor
Filaments of lamp
Transistors
Formula of resisance interms of resistivity
R=ρ (rho) L/A
A wire of length ‘l’ has resistance R.This wire is stretched to twice it’s original length find it’s new resistance.
a.R/2
b.2R
c.R/4
d.4R
d.4R
When length increases by 2 times area
a.Increases by 2 times A/2
b.Decreases by 2 times A/2
b.Decreases by 2 times A/2
A wire of resistance ‘R’ is compressed to half of it’s original length.Find it’s new resistance.
a.2R
b.R/2
c.R/4
d.4R
c.R/4
A wire of resistance 3ohm is stretched to 10 times it’s original length.Find new resistance.
R’=n²R
=10²x3
=100x3
=300ohm
If a wire of resistance R I’d stretched n times the resistance becomes
a.n²/R
b.R/n²
c.nR
d.n²R
d.n²R
The wire of resistance 2ohm is stretched 2 times the resistance will be
a. 2 ohm
b.4 ohm
c.8 ohm
d.7 ohm
c.8 ohm
A wire of resistance 2 ohm is stretched 1.5 time the resistance of stretched wire becomes
a.1.5ohm
b.3.5ohm
c.6 ohm
d.4.5 ohm
d.4.5 ohm
Resistivity ρ (rho) depends upon
Temperature
Materials
The electrical resistance of metals
a.increase with increase with temperature
b.decrease with increase in Temperature
c.is independent of temperature
d.increases for some metals and decreases fo others
a.increase with increase with temperature
Constantan wire(Resistance constant) is used for making Standard resistance because it has
a.low sp.resistance
b.high sp.resistance
c.Negligible temperature coefficient of resistance
d.High melting point
c.Negligible temperature coefficient of resistance
If n,e,T and m represent electron Density,charge,relaxation time and mass of an electron respectively,then the resistance of a wire of length l and cross section are
a.ml/ne²TA
b.mTA/ne²l
c.ne²TA/ml
d.ne²l/TA
a.ml/ne²TA
A piece of aluminium and germanium temperature is increased from T1K to T2K. Then resistance is:-
a. Each of them increases
b. Each of them decreases
c. Aluminium increases germanium decreases
d. Aluminium decreases germanium increases
c. Aluminium increases germanium decreases
Resistivity of alloy=R alloy .The resistivity of
constituent metals=R metals. Then usually
a.Ra>Rm
b.Ra=Rm
c.R a<R>=<=R metal</R>
d.R alloy>=<=R metal
Conductivity is the
a reciprocal of current density b.reciprocal of resistivity
c. reciprocal of resistance
d. same as current
b.reciprocal of resistivity
The specific resistance resistivity of a wire varies with
a. length
b. cross section
c.mass
d.material
d.material
To wire A and b are made up of copper. Both wires are 1 m long but why are a is 1 mm take and wire B is 2 mm thick the specific resistance is
a .more for A
b.same for both A and B
c. cannot be compared
d. same for both a and b
b same for both A and B
Numerical
A piece of copper wire has resistance are. It is stretched to half of its radius. The new resistance of copper wire becomes
a.R
b.R/4
c.R/16
d.16R
c.16R
Why are resistance 5.5 ohm is drawn and uniformly so that its length increases twice. Then the new resistance is
a.5.5Ohm
b.11Ohm
c.22Ohm
d.44Ohm
c.22ohm
The resistance of wire for 4ohm when it is spent through 180° and twisted together then new resistance will be:-
a.1ohm
b.2ohm
c.4ohm
d.8ohm
a.1ohm
One of the following is an Ohmic conductor
a.Transistor
b.Vacuum Tube
c.Electrolyte
d.Nichrome wire
d.Nichrome wire
