Tag: force on current carrying conductor

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Multiple choice 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

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 

  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 $0 N-m$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Work done to rotate a magnet by 180 degrees is W = MB(cos(0) - cos(180)) = MB(1 - (-1)) = 2MB. W = 2 * 1.5 * 0.22 = 0.66 J. In the opposite position (180 degrees), the torque tau = MB sin(180) = 0.

Multiple choice 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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

Multiple choice 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

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. $(B _H =4 \times 10^{-5} \ Wbm^{-2})$

  1. 0.4 m

  2. 0.2 m

  3. 0.5 m

  4. 0.8 m
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice 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

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

  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. $\vec t = \vec M.\vec B$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The torque on a magnetic dipole (current loop) in a magnetic field is defined by the vector cross product of the magnetic moment and the magnetic field: tau = M x B.

Multiple choice 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

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

  1. 0.01 N/m

  2. 0.001 N/m

  3. 1.1 N/m

  4. 0.8 N/m
Reveal answer Fill a bubble to check yourself
A Correct answer
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 $

Multiple choice 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

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 $\vec{\tau}$

  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 $\vec{B}$.
Reveal answer Fill a bubble to check yourself
A,D Correct answer
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.

Multiple choice 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

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

  1. torque only

  2. force only

  3. neither torque nor force

  4. both
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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

Multiple choice 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

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:

  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. $\dfrac{|\overline{\mu} _1|}{|\overline{\mu} _2|} = \dfrac{1}{\sqrt{2}}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Original moment M1 = I * L^2. After folding, the two halves are perpendicular. The new moment M2 is the vector sum of the moments of the two halves. Each half has moment M/2. The resultant is sqrt((M/2)^2 + (M/2)^2) = M/sqrt(2). The ratio M1/M2 = L^2 / (L^2/sqrt(2)) = sqrt(2).

Multiple choice 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

The plane of a rectangular loop of wire with sides $0.05 m$ and $0.08 m$ is parallel to a uniform magnetic field of induction $1.5\times 10^{-2}T$ . A current of $10.0 A$ flows through the loop. If the side of length $0.08 m$ is normal and the side of length $0.05 m$ is parallel to the lines of field, then the torque acting on it is

  1. $6000N-m$ 

  2. $zero$ 

  3. $1.2\times 10^{-2}N-m$

  4. $6\times 10^{-4}N-m$ 
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Torque on the loop $\vec{\tau} = \vec{\mu} \times \vec{B}$ where $\vec{\mu}=i\vec{A}$ is the magnetic moment of the loop and $\vec{B}$  is the magnetic field.
$ \therefore \tau = i\vec{A} \times \vec{B}$
Since $\vec{B}$ is in the plane of the loop, $\vec{A} \perp \vec{B}$
$ \therefore \vec{\tau} = 10 \times ( 0.05 \times 0.08) \times( 1.5 \times 10^{-2})= 6 \times 10^{-4}N-m$