Tag: physics

Questions Related to physics

The magnetic moment of a magnetic wire of length L is M . It is bent at its middle point such that of makes an angle of ${60^0}$ . The magnetic moment of this bent wire will be :

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. M

  2. M/2

  3. 2M

  4. $\frac{{\sqrt 3 }}{{2M}}$

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Correct Option: C

If the net force acting on the loop is zero then : 

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. no torque acts on loop

  2. loop performs translational motion

  3. torque can act on the loop if lines of force do not coincide

  4. both a) and b)

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Correct Option: A
Explanation:

If the net force acting on the loop is zero then, 


1) The loop performs rotational motion.


2) No torque acts on the loop.

The correct option is A.

A bar magnet of magnetic moment 1.5 J/T is along the direction of the uniform magnetic field of 0.22T. The work done in turning the magnet opposite to the field direction and the torque required to keep in that position are 

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. $0.33J$ and $0.33 N-m$

  2. $0.66J$ and $0.66 N-m$

  3. $0.33J$ and $0 N-m$

  4. $0.66J$ and $0 N-m$

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Correct Option: D

On applying a uniform magnetic field on a current-carrying coil the coil rotates in such a way that its plane

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. becomes perpendicular to magnetic field

  2. becomes parallel to magnetic field

  3. makes an angle of $45^o$ with the magnetic field

  4. makes any angle with the magnetic field

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Correct Option: A
Explanation:

On applying a uniform magnetic field on a current-carrying coil, the lines of force are at right angle to the plane of coil. Hence, the coil rotates in such a way that its plane becomes perpendicular to magnetic field.

A very long magnet of pole strength 16 A-m is placed vertically with its one pole on the table. At what distance from the pole, there will be a neutral point on the table. $(B _H =4 \times 10^{-5} \ Wbm^{-2})$

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. 0.4 m

  2. 0.2 m

  3. 0.5 m

  4. 0.8 m

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Correct Option: A

The torque $(\vec t)$ experienced by a current - loop of magnetic moment $(\vec M)$ placed in magnetic field $\vec B$ is -

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. $\vec t = \vec M \times \vec B$

  2. $\vec t = \vec B \times \vec M$

  3. $\vec t = \frac{\vec M}{\vec B}$

  4. $\vec t = \vec M.\vec B$

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Correct Option: A

A coil of area 0.01 m$^2$ is lying in a perpendicular magnetic field of 0.1 Tesla. If a current of 10 A is passed in it then the maximum torque acting on the coil will be

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. 0.01 N/m

  2. 0.001 N/m

  3. 1.1 N/m

  4. 0.8 N/m

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Correct Option: A
Explanation:

Magnetic moment = $ I \vec A = 0.01 \times 10   A/m^2$ perpendicular to the field.
Maximum torque on the magnetic moment is when angle between magnetic moment and the field is $90^{\circ}= (I \vec A ) \times \vec B = I A B = 10 \times 0.01 \times 0.1 = 0.01 Nm $

A flat coil carrying a current has a magnetic moment $\vec{\mu}$. It is placed in a magnetic field $\vec B$. The torque on the coil is $\vec{\tau}$

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. $\vec{\tau} = \vec{\mu} \times \vec B$

  2. $\vec{\tau} = \vec{B} \times \vec{\mu} $

  3. $|\vec{\tau}| = \vec{\mu} \cdot \times \vec B$

  4. $\vec{\tau}$ is perpendicular to both $\vec{\mu}$ and $\vec{B}$.

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Correct Option: A,D
Explanation:

The magnetic moment is defined as a vector relating the aligning torque on the object from an externally applied magnetic field to the field vector itself. The relationship is given by:

$ \tau = \vec{\mu} \times \vec{B} $

where  $\tau$ is the torque acting on the dipole and $B$ is the external magnetic field, and $\mu$  is the magnetic moment. Direction of torque is given by the right hand rule.

A current-carrying loop suspended freely in a uniform magnetic field  will experience 

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. torque only

  2. force only

  3. neither torque nor force

  4. both

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Correct Option: A
Explanation:

A current carrying loop behaves as a magnetic dipole. and we know that a dipole placed in uniform magnetic field only experiences torque.

Asteady current 'I' flows in a small square loop of wire of side $L$ in a horizontal plane. The loop is now folded about its middle such that half of it lies in a vertical plane. Let $\overline{\mu} _1$ and $\overline{\mu} _2$ respectively denote the magetic moments of the current loop before and after folding. Then:

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. $\overline{\mu} _2 = 0$

  2. $\overline{\mu} _1$ and $\overline{\mu} _2$ are in the same direction

  3. $\dfrac{|\overline{\mu} _1|}{|\overline{\mu} _2|} = \sqrt{2}$

  4. $\dfrac{|\overline{\mu} _1|}{|\overline{\mu} _2|} = \dfrac{1}{\sqrt{2}}$

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Correct Option: C