Download gfgf-odt - Ranjit Tutorials

This is Physics Class 12 Electric Charges and Fields CBSE Online Test 01. Students are
instructed to read all the points carefully before clicking the START TEST button.
General Instructions:
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Students must not use calculators and any other unfair means while taking the test.
The duration of the test is 30 minutes. You will not be able to submit the test after the
time is over.
There will be total 15 MCQ in this test.
The test will consist of only objective type multiple choice questions requiring students to
mouse-click their correct choice of the options against the related question number.
For every question there will be only one correct option out of the four given options.
Each question carries one mark. There is no negative marking for incorrect choice.
For moving to the next question, click on "Next" at the bottom of the screen.
Questions can be answered in any order in given time.
For moving to previous question click on "PREVIOUS" at the bottom of the screen.
Students can mark the question for review too.
Students can make changes in their choice of options before clicking the "SUBMIT"
button.
After completing all the questions, click "SUBMIT" button. A message will be displayed
on the screen "Do you really want to submit ?". If student click on "NO", the will be
redirected to the test page again and if they press "YES", the result will be displayed on
the screen with details of questions attempted.
which of the following methods can be used to charge a metal sphere positively without touching
it . Select the best
Bring a negatively charged rod near the sphere and touch it to ground for a short while
Rub it with a piece of fur
Connect the positive terminal a battery and float the other end of the battery
Rub it with a piece of silk
Question : 1 - Not Attempted
A wire is perpendicular to the plane of the paper. A ring of compass needles surrounds the wire
in the plane of the paper with center of ring being the center of the wire .Initially there is no
current in the wire. What happens after a steady dc current is established in the wire?
The needles become parallel to each other
The needles become tangential to the ring of which they are a part
nothing happens
some needles become parallel to each other while others are uneffected
The current carrying wire has a magnetic field around it and the lines of force are in the form of
concentric circles with their centers on the wire.
Question : 2 - Not Attempted
Which of the following is most general charachteristic of Magnetic field
The magnetic field exerts a force F⃗
only on any magnets present in the field.
The magnetic field exerts a force F⃗
only on any iron filings
The magnetic field exerts a force F⃗
on any other particle
The magnetic field exerts a force F⃗
on any other moving charge or current that is present in the field.
A moving charge experiences a force in a magnetic field called magnetic Lorentz force given
byF⃗ =q(v⃗ ×B⃗ )
.This force acts only if the particle (i) has charge q(ii) has a non zero velocity v and (iii) does not
move parallel or anti parallel to the magnetic field B. A current carrying conductor placed in a
magnetic field experiences a force given byF⃗ =Il⃗ ×B⃗
Question : 3 - Not Attempted
which of the following best describes the difference between electric and magnetic fields
The electric force acts in the direction perpendicular to electric field, whereas the magnetic force
acts parallel to the magnetic field
The electric force acts on positive charges in the electric field, whereas the magnetic force acts
on negative charges in the magnetic field
The electric force acts on negative charges in the electric field, whereas the magnetic force acts
on positive charges in the magnetic field
The electric force acts in the direction of the electric field, whereas the magnetic force acts
perpendicular to the magnetic field
The electrostatic force experienced by a positive charge q placed in an electric field is
F⃗ E=qE⃗
. The force acts in the direction of the electric field.The magnetic force acting on a charge of
magnitude q moving with a velocity 'v' is F⃗ M=q(v⃗ ×B⃗ ).This acts in a direction
perpendicular to the plane containing the vectors.v⃗ and B⃗
Question : 4 - Not Attempted
Which of these equations is the correct expression for force on a charge in magnetic field
F⃗ =qv⃗ ×2B⃗
F⃗ =qv⃗ ×B⃗
F⃗ =q2v⃗ ×B⃗
F⃗ =3qv⃗ ×B⃗
A charged particle moving in a magnetic field experiences magnetic Lorentz force given by
F⃗ =q(v⃗ ×B⃗ )
Question : 5 - Not Attempted
direction of magnetic force on a positive charge moving in a magnetic field is given by
thumb rule
right hand rule
two hand rule
left hand rule
The force experienced by a charged particle in a magnetic field is given by F⃗ =q(v⃗ ×B⃗
.The right hand rule for vector product can be used to determine the direction of F⃗
)
.
Question : 6 - Not Attempted
Lorentz Force generally refers to
force experienced by a charge due to combined action of electrical and magnetic fields
force experienced by a charge due to combined action of electrical fields
force experienced by a charge due to combined action of electrical,magnetic field and
gravitational field
force experienced by a charge due to action of magnetic fields
A moving charge experiences a force in a magnetic field called magnetic Lorentz force given by
F⃗ =q(v⃗ ×B⃗ )
Question : 7 - Not Attempted
correct unit of magnetic field is
ampere turns
Tesla
Newton coulombs
Amperes
The SI unit of magnetic field is Tesla (T)
Question : 8 - Not Attempted
If a current I is flowing in a staight wire parallel to x axis and magnetic field is there in the y axis
then
The wire experiences force in y direction
The wire experiences force in z direction
The wire experiences no force
The wire experiences force in x direction
force experienced by a conductor of length l carrying current I placed in magnetic field B is
given by F⃗ =Il⃗ ×B⃗
.
Il⃗ =∣∣Il⃗ ∣∣i^ and B⃗ =∣∣B⃗ ∣∣j^F⃗ =Il⃗ ×B⃗ =∣∣Il⃗ ∣∣i^×∣∣B⃗ ∣∣j^=IlB(i^×j^)=IlB(k
^)
.The force acts along the positive z axis.
Question : 9 - Not Attempted
correct expression for force on a current carrying conductor of length dl in a magnetic field is
F⃗ =ϵ0Idl→×B⃗
F⃗ =Idl→×2B⃗
F⃗ =2Idl→×B⃗
F⃗ =Idl→×B⃗
force experienced by a conductor of length l carrying current I placed in magnetic field B is
given by F⃗ =Il⃗ ×B⃗
.Here l⃗ =dl⃗
.
Question : 10 - Not Attempted
The magnitude of the magnetic field due to a circular coil of radius R carrying a current I at an
axial distance x from the centre is
B=μ0IR22(x2+R2)32
B=μ0IR23(x2+R2)32
B=μ0IR32(x2+R2)32
B=μ0IR22(x2+R2)35
magnetic field at a point located at a distance x from the center of the coil of radius R carrying
current along its axis is B=μ0IR22(x2+R2)32
Question : 11 - Not Attempted
Consider the motion of a charged particle in a uniform magnetic field directed into the paper.If
velocity v of the particle is in the plane of the paper the charged particle will
describe a hyperbola
describe an ellipse
describe a circle
describe a straight line
The charged particle experiences magnetic Lorentz force given byF⃗ =q(v⃗ ×B⃗ )
.This force acts in the plane of the paper perpendicular to the velocity vector at all points on the
plane. Magnetic Lorentz force acts like a centripetal force, causing the particle to move in a
circle.
Question : 12 - Not Attempted
cyclotron is used to
accelerate charged particles or ions to low voltages
accelerate charged particles or ions to high energies
accelerate charged particles or ions to high voltages
decelerate charged particles or ions to high voltages
Cyclotron is a particle accelerator, which uses electric field to accelerate the charged particle and
magnetic field to make it move in a circular path. During acceleration in the electric field, the
particle acquires high energies of the order of a few million electron volts.
Question : 13 - Not Attempted
cyclotron frequency of a charged particle having charge q and mass m in a cyclotron producing
magnetic field B is
qBπm
q2B2πm
qB2πm
qB22πm
A particle of charge q moving with a speed v on entering a magnetic field B, experiences
magnetic Lorentz force which acts as a centripetal force.
here, ν
is the cyclotron frequency.
Question : 14 - Not Attempted
what is common to both biot savart law and ampere's law
nothing in common
Both relate the magnetic field and the current, and both express the same physical consequences
of a varying electrical current
Both relate the magnetic field and the current, and both express the same physical consequences
of a steady electrical current
Both relate the magnetic field and the current density, and both express the same physical
consequences of a steady electrical current
Both Biot- Savart’s lawdB⃗ =μ04πIdl⃗ ×r^r2
and ampere’s circuital law∮B⃗ ⋅dl⃗ =μ0I
deal with the consequences of steady current. Ampere’s circuital law is to Biot- savart’s law as is
Gauss’s law to Coulomb’s law in electrostatics.
Question : 15 - Not Attempted
According to Ampere's circuital law
∮B⃗ .dl→=μ0I
∮B⃗ .dl→=I
∮B⃗ .dl→=2πμ0I
∮B⃗ .dl→=πμ0I
the expression for Ampere’s circuital law is ∮B⃗ ⋅dl⃗ =μ0I
where I is the current included in the surface bounded by the line integral.