Tag: physics

Questions Related to physics

Consider an experiment where Electric current is flowing in a wire. It is observed that clockwise magnetic field is produced around the wire. A teacher decides to reverse the direction of source battery which results in reversal of electrical current. What will be the effect on magnetic field?

physics electromagnetism magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop field due to a current carrying coil oersted experiment

  1. Magnetic field disappears

  2. Direction of field lines reverse

  3. Field lines changes direction to parallel to wire

  4. None of the above

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Correct Option: B
Explanation:

Using Right Hand thumb rule, as current direction reverses, you need to reverse the hand and direction of magnetic field reverses.

Axis of a solid cylinder of infinite length and radius $R$ lies along $y$-axis. It carries a uniformly distributed corrent I along +$y$ direction. Magnetic field at a point $(R/2,y,R/2)$ is 

physics electromagnetism magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop field due to a current carrying coil oersted experiment

  1. $\cfrac{\mu _{0}I}{4\pi R}\left(\hat{i}-\hat{k}\right)$

  2. $\cfrac{\mu _{0}I}{2\pi R}\left(\hat{j}-\hat{k}\right)$

  3. $\cfrac{\mu _{0}I}{4\pi R}\hat{j}$

  4. $\cfrac{\mu _{0}I}{4\pi R}\left(\hat{j}+\hat{k}\right)$

Show answer
Correct Option: A

A current carrying circular loop of radius R is placed in the x-y plane with centre at the origin. Half of the loop with x > 0 is now bent so that it now lies in the $y-z$ plane.

physics electromagnetism magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop field due to a current carrying coil oersted experiment

  1. The magnitude of magnetic moment now diminishes.

  2. The magnetic moment does not change.

  3. The magnitude of $\bar B$ at $(0,0, z), z$>>R increases.

  4. The magnitude of $\bar B$ at $(0, 0, z), z$>>R is unchanged.

Show answer
Correct Option: A
Explanation:

For a circular loop of radius R carrying current, I placed in $x-y$ plane, the magnetic moment $M= I\,\,\pi R^2$. It acts perpendicular to the loop i.e., along with the z-direction. When half of the current loop is bent in y-z plane, the magnetic moment due to half current loop in x-y plane,$ M _1 = I \left (\dfrac {\pi R^2}{2} \right )$ acting along z-direction.
Magnetic moment due to half current loop in y-z plane,$ M _2 = I \left (\dfrac {\pi R^2}{2} \right )$ along x-direction.
Effective magnetic moment due to entire bent current loop,
$M'$ =$\sqrt{{M _{1}^{2}}+ {M _{2}^{2}}} $=$\sqrt {{\left (\dfrac{I \pi R^2}{2} \right )^2}+{\left (\dfrac{I \pi R^2}{2} \right )^2}}$
$M'=\dfrac{I\pi R^2}{2}\sqrt2 <M$
i.e., magnetic moment diminishes.

Why does toroid have a higher magnetic field than a solenoid?

physics magnetic effect of electric current magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop field due to a current carrying coil magnetic field lines due to current magnetic field due to current carrying conductor magnetic field on the axis of a toroid

  1. It is magnetically efficient.

  2. It is a straight core.

  3. It has an open loop core.

  4. It has a closed loop core.

Show answer
Correct Option: D
Explanation:
Due to the symmetry and being closed loop core.
Totoid has higher magnetic field and thus higher inductor and Q-facator

Which among the following is not an electronic component used in constructing a toroid?

physics magnetic effect of electric current magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop field due to a current carrying coil magnetic field lines due to current magnetic field due to current carrying conductor magnetic field on the axis of a toroid

  1. copper wires

  2. laminated iron

  3. ferrite core

  4. aluminium powder

Show answer
Correct Option: D
Explanation:
Toroids are inductors and transformers which use magnetic cores.
These cores are of ferromagnetic material such as
Laminated iron, iron powder or ferrite.

The leakage flux of a toroid is less because

physics magnetic effect of electric current magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop field due to a current carrying coil magnetic field lines due to current magnetic field due to current carrying conductor magnetic field on the axis of a toroid

  1. It is asymmetrical.

  2. It has an open-loop core.

  3. It is symmetrical.

  4. It has a straight core.

Show answer
Correct Option: C
Explanation:
Toroidal is a surface of revolution with hole in middle.
This is a solid body used for toroid production.
The advantage of this shape is that, due to its symmetry amount of magnetic flux that escapes outside is low.

Which of the following is true for a toroid?

physics magnetic effect of electric current magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop field due to a current carrying coil magnetic field lines due to current magnetic field due to current carrying conductor magnetic field on the axis of a toroid

  1. low inductance and Q factor

  2. high inductance and Q factor

  3. high inductance and low Q-factor

  4. low inductance and high Q-factor

Show answer
Correct Option: B
Explanation:

Due to the symmetry and being closed loop core.
Toroid has higher magnetic field and thus higher inductor and Q-factor

A toroid is                  solenoid

physics magnetic effect of electric current magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop field due to a current carrying coil magnetic field lines due to current magnetic field due to current carrying conductor magnetic field on the axis of a toroid

  1. a finite

  2. an endless

  3. straight

  4. either A or B

Show answer
Correct Option: B
Explanation:

A Toroid is a solenoid which is bent in the form of a ring with its both the ends joined together.  Since both the ends are merged, it appears endless.

A solenoid of length 0.4 m, having 500 turns and 3A current flows through it. A coil of radius 0.01 m and have 10 turns and carries current of 0.4 A has to placed such that its axis is perpendicular to the axis of solenoid ,then torque on coil will be

physics magnetic effect of electric current magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop field due to a current carrying coil magnetic field lines due to current magnetic field due to current carrying conductor magnetic field on the axis of a toroid

  1. $5.92\times 10^{-7} N.m$

  2. $5.92\times 10^{-5} N.m$

  3. $5.92\times 10^{-4} N.m$

  4. $5.92\times 10^{-3} N.m$

Show answer
Correct Option: A
Explanation:
Magnetic field due to larges solenoid
$B=\dfrac {\mu _{0} NI}{l}=\dfrac {4\times 10^{-7}\times 500 \times 3}{0.4}$
$N=500$ 
$I=3$
$l=0.4$
Torque $M$ solenoid $I\times $ Area of corn section $\times B$
$=0.4\times \pi 0.01^{2}\times 4\pi \times \dfrac{10^{-7}\times 500 \times 3}{0.4}$
 orque $=\pi.0.01^{2} \times 4\pi \times 10^{-7}\times 500 \times 3$
Torque $=5.92\times 10^{-7}N-m$

A coil of many circular turns of wire wrapped in a shape of a cylinder forms a ______

physics magnetic effect of electric current magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop field due to a current carrying coil magnetic field lines due to current magnetic field due to current carrying conductor magnetic field on the axis of a toroid

  1. torroid

  2. solenoid

  3. conductor

  4. insulator

Show answer
Correct Option: B