CBSE Questions for Class 12 Medical Physics Moving Charges And Magnetism Quiz 2 - MCQExams.com

The restoring couple in the moving coil galvanometer is due to
  • current in the coil
  • magnetic field of the magnet.
  • material of the coil.
  • twist produced in the suspension wire.
There is $$10$$ units of charge at the centre of a circle of radius $$10m$$. The work done in moving one unit of charge around the circle once is 
  • $$0$$
  • $$10$$ units
  • $$100$$ units
  • $$1$$ unit
A circular coil of one turn and area $$A$$ carrying a current has a magnetic dipole moment $$M$$. The current through the coil is :
  • $$M A$$
  • $$\dfrac{A}{ M}$$
  • $$\dfrac{M}{A}$$
  • $$\dfrac{M}{A ^{2}}$$
The magnetic force acting on a charged particle of charge $$-2\mu c$$ in a magnetic field of 2T acting in y direction, when the particle velocity is $$(2\hat{i}+3\hat{j})\times10^6\;ms^{-1}$$, is :
  • 8N in z direction
  • 8N in -z direction
  • 4N in z direction
  • 8N in y direction
A proton is fired with a speed of $$2\times10^6$$ m/s at an angle of $$60^o$$ to the X- axis. If a uniform magnetic field of $$0.1T$$ is applied along the Y- axis, the force acting on the proton is
  • $$1.63 \times 10^{-14} N$$
  • $$1.6 \times 10^{-14} N$$
  • $$3.23 \times 10^{-14} N$$
  • $$3.2 \times 10^{-14} N$$
A flat circular coil carrying current has a magnetic moment $$\mu $$. Then ,
a. $$\mu $$  has only magnitude, it does not have direction
b. The direction of $$\mu $$  is along the normal to the plane of the coil
c. The direction of $$\mu $$  depends on the direction of current flow
d. The direction of $$\mu $$  does not change if the current in the coil is reversed
  • a only is correct
  • b and c only are correct
  • d only is correct
  • b and d only are correct
The radial magnetic field is used in a suspended coil galvanometer to provide
  • a uniform torque on the coil
  • maximum torque on the coil in all positions
  • a uniform and maximum torque in all positions

    of the coil
  • a non uniform torque on the coil
A moving coil type of galvanometer is based upon the principle that
  • coil carrying current experiences a torque in magnetic field.
  • a coil carrying current produces a magnetic field.
  • a coil carrying current experiences impulse in a magnetic field.
  • a coil carrying current experiences a force in a magnetic field.
An electron is moving vertically downwards at any place. The direction of magnetic force acting on it due to horizontal component of earth's magnetic field will be
  • towards east
  • towards west
  • towards north
  • towards south
When the radius of the circular current carrying coil is doubled and the current in it is halved,then magnetic dipole moment of the coil originally four units becomes
  • 4 units
  • 8 units
  • 16 units
  • 32 units
The correct statement about magnetic moment is :
  • it is a vector quantity
  • its unit is $$Am^2$$
  • its dimensions are $$[AL^2]$$
  • all of the above
The correct expression for Lorentz force is
  • $$q[\vec E+(\vec B\times \vec V)]$$
  • $$q[\vec E+(\vec V\times \vec B)]$$
  • $$q(\vec V\times \vec B)$$
  • $$q\vec E$$
A current carrying conductor
  • Experiences a force when it is in magnetic field
  • Does not experience a force when it is in magnetic field
  • Experiences the force only when the field is electromagnetic in nature
  • none of the above
In a moving coil galvanometer, the magnetic pole pieces are made cylindrical and a soft iron core is placed at the centre of the coil,the purpose for doing so is:
  •  to make the magnetic field strong
  •  to make the magnetic field strong and radial
  •  to make the magnetic field uniform
  •  to make the magnetic field strong and uniform
A magnetic field cannot exert any force on a 
  • Moving magnet
  • Stationary magnet
  • Moving charge
  • Stationary charge
A magnetic field can exert force on a
  • stationary magnet
  • moving charge
  • moving magnet
  • all of these
The correct expression for Ampere's law is :
  • $$\int B.dl=\sum i$$
  • $$\int B.dl=\dfrac {1}{\sum i}$$
  • $$\int B.dl=\mu_0\sum i$$
  • $$\int B.dl=\dfrac {\sum i}{\mu_0}$$
An electron and a proton travel with equal speeds and in the same direction, at $$90^o$$ to a uniform magnetic field. They experience forces which are initially
  • in opposite direction and differ by a factor of about 1840
  • in the same direction and differ by a factor of about 1840
  • equal in magnitude but in opposite directions
  • identical
In a moving cell galvanometer, we use a radial magnetic field so that the galvanometer scale is
  • logarithmic
  • exponential
  • linear
  • none of the above
If a long hollow copper pipe carries a direct current, the magnetic field associated with the current will be :
  • only inside the pipe
  • only outside the pipe
  • both inside and outside the pipe
  • neither inside not outside the pipe
Find the magnetic field intensity due to a thin wire carrying current $$I$$ in the figure :

144163_5d0fe50699c149a98bad57ee524c2656.png
  • $$\dfrac {\mu_0i}{2\pi R}(\pi -a+tan a)$$
  • $$\dfrac {\mu_0i}{2\pi R}(\pi -a)$$
  • $$\dfrac {\mu_0i}{2\pi R}(\pi +a)$$
  • $$\dfrac {\mu_0}{2\pi R}(\pi +a-tan a)$$
Two parallel wires carrying current in the same direction attract each other because of
  • potential difference between them
  • mutual inductance between them
  • electric forces between them
  • magnetic forces between them
A current-carrying loop lying in a magnetic field behaves like a
  • magnetic dipole
  • magnetic pole
  • magnetic material
  • non-magnetic material
Suppose that a proton traveling in vaccum with velocity $$u_1$$ at right angles to a uniform magnetic field experiences twice the force that an $$\alpha$$ particle experiences when it is traveling along the same path with velocity $$u_2$$.The ratio $$\left (\dfrac {u_1}{u_2}\right )$$ is
  • $$\dfrac {1}{2}$$
  • $$1$$
  • $$2$$
  • $$4$$
A current of $$1\  A$$ is flowing in a coil of $$10$$ turns having radius $$10\ cms$$. Its magnetic moment will be
  • $$3140\ Am^2$$
  • $$100\ Am^2$$
  • $$\mu_0 \ Am^2$$
  • $$0.314\ Am^2$$
A bar magnet for dipole moment $$10^4\ JT^{-1}$$ is free to rotate around a horizontal plane. A horizontal magnetic field $$4\times 10^{-5}\ T$$ exists on the space. Find the work done in rotating the magnet slowly from a direction parallel to the field to a direction $$60^0$$ from the field.
  • $$0.1\ J$$
  • $$0.2\ J$$
  • $$0.4\ J$$
  • $$0.5\ J$$
A proton enters a perpendicular magnetic field of 20 Tesla. If the velocity of proton is $$4 \times 10^7 m/s$$ then the force acting on it will be :
  • 1.28 Newton
  • $$1.28 \times 10^{-11} $$ Newton
  • 12.8 Newton
  • $$12.8 \times 10^{-11} $$ Newton
Current $$I$$ is flowing in a coil of area $$A$$ and number of turns is $$N$$, then magnetic moment of the coil is $$M$$ equal to
  • $$NIA$$
  • $$NI/A$$
  • $$NI/\sqrt A$$
  • $${N}^{2}AI$$
If a bar magnet in magnetic moment $$m$$ is deflected from an angle $$\theta$$ in a uniform magnetic field of induction $$B$$, the work done in reversing the direction is 
  • $$MB\sin\theta$$
  • $$MB$$
  • $$MB(1-\cos\theta)$$
  • $$MB\cos\theta$$
A coil $$(8cm\times4cm)$$ carries a current $$2A$$ and has $$200$$ turns. Find the magnetic dipole moment.  
  • $$12.8Am^2$$
  • $$1.28Am^2$$
  • $$6.4Am^2$$
  • $$0.64Am^2$$
Find the ratio of magnetic dipole moment to angular momentum in a hydrogen like atom :
  • $$\displaystyle \frac {e}{m} $$
  • $$\displaystyle \frac {e}{2m} $$
  • $$\displaystyle \frac {e}{3m} $$
  • $$\displaystyle \frac {2e}{m} $$
  • $$\displaystyle \frac {3e}{m} $$
A charge q is moving with a velocity v parallel to a magnetic field B. Force on the charge due to magnetic field is
  • q v B
  • q B/v
  • zero
  • B v/q
The magnetic dipole moment of current loop is independent of
  • number of turns
  • area of loop
  • current in the loop
  • magnetic field in which it is laying
What name is given to a cylindrical coil of diameter less than its length ?
  • Lactometer
  • Barometer
  • Bolenoid
  • Solenoid
A charged particle moves through a magnetic field in a direction perpendicular to it. Then the
  • velocity remains unchanged
  • speed of the particle remains unchanged
  • direction of the particle remains unchanged
  • acceleration remains unchanged
An electron moving to the east in a horizontal plane is deflected towards south by a magnetic field. The direction of this magnetic field is
  • Towards north
  • Towards west
  • Downwards
  • Upwards
The magnetic field produced by a current-carrying wire at a given point depends on
  • the current passing through it.
  • the voltage across it
  • the power through it
  • all
When a current in a circular loop is equivalently replaced by a magnetic dipole
  • the pole strength $$m$$ of each pole is fixed
  • the distance $$d$$ between the poles is fixed
  • the product $$md$$ is fixed
  • None of these
In a current carrying conductor, if the direction of magnetic field and that of the current are mutually perpendicular to each other, then the force acting on the conductor will be
  • perpendicular to both
  • perpendicular to direction of current
  • perpendicular to direction of field.
  • none
1 gauss is equal to
  • $$10^4T$$
  • $$10^{-4}T$$
  • $$10^3 T$$
  • none of these
A conducting rod AB moves parallel to X-axis in a uniform magnetic field, pointing in the positive X-direction. The end A of the rod gets

206435_c04f5291f67d458d9b8f8657b01a1450.png
  • positively charged
  • negatively charged
  • neutral
  • first positively charged and then negatively charged
The formation of a dipole is due to two equal and dissimilar point charges placed at a
  • short distance
  • long distance
  • above each other
  • None of these
If the current is doubled, the deflection is also doubled in
  • a tangent galvanometer
  • a moving-coil galvanometer
  • both
  • None of these
Ampere rule is used to find the
  • direction of current
  • direction of magnetic field
  • direction of motion of the conductor
  • magnitude of current
A magnetic field exerts no force on:
  • A magnet
  • An unmagnetised iron bar
  • A moving charge
  • Stationary charge
Scale used in moving coil galvanometer is :
  • function scale
  • linear scale
  • exponential scale
  • none of these
An electron of charge $$e$$ and mass $$m_e$$ moves in a circular path of radius $$r$$ in a uniform magnetic field $$B$$.
The Kinetic Energy of the electron can be described by the expression
  • $$\dfrac{1}{2}m_ev^2$$
  • $$evBr$$
  • $$\dfrac{1}{2}evBr$$
  • $$2evBr$$
  • $$\sqrt{\dfrac{1}{2}evBr}$$
A charged particle moves in a magnetic field. The only force influencing the particle is the force caused by the magnetic field.
During the particle's movement in the magnetic field, what will NOT change?
  • the particle's velocity
  • the particle's acceleration
  • the particle's speed
  • the particle's momentum
  • the particle's position
In ballistic galvanometer, the frame on which the coil is wound is non-metallic to:
  • Avoid the production of induced emf
  • Avoid the production of eddy currents
  • Increase the production of eddy currents
  • Increase the production of induced emf
A current carrying conductor.
  • Experience a force when it is in magnetic field
  • Does not experience a force when it is in magnetic field
  • Experiences the force only when the field is electromagnetic in nature
  • None of the above
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