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Bar Magnet as an Equivalent Solenoid

Q: Force between two identical short bar magnets whose centres are \$ r\$ metre apart is \$4.8 N\$ when their axes are in the same line. If the separation is increased to \$2r\$ metre, the force between them is reduced to

GivenTwo bar magnets placed axially at distance rForce between them is 4.8 NSolutionForce between two Magnetic dipoles is\$F=\frac{\mu_{0}*6M_{1}M_{2}}{4\pi*d^{4}}\$F is inversely proportional to \$r^{4}\$Therefore New Force will be\$F'=\frac{F}{2^{4}}\$Because new d will be 2rF'=4.8/16=0.3NThe correct answer is 0.3N

Q: Write SI unit of magnetic dipole moment.

Magnetic dipole moment \$M = Current \times Area\$So, its SI unit is \$A \ m^2\$

Q: A closely wound solenoid of 800 turns and area of cross section \$2.5\times 10^{-4} m^2\$ carries a current of \$3.0\, A\$. Explain the sense in which the solenoid acts like a bar magnet. What is its associated magnetic moment?

Given: \$n=800,\$\$A=2.5\times 10^{-4}m^2,\$\$I=3.0A\$A magnetic field develops along the axis of the solenoid. Therefore current-carrying solenoid acts like a bar magnet.\$m=nIA=800\times 3\times 2.5\times 10^{-4}JT^{-1}\$ \$=0.6JT^{-1}\$ along the axis of the solenoid.

Q: Distinguish between a bar magnet and a solenoid.

Bar magnetSolenoidIt has its natural magnetism. Its magnetism is a type of artificial magnetism.Its magnetism cannot be increased or decreased by any other external way.Its magnetism can be destroyed or it can be stopped.Its magnetism does not depend on any external applied factor. Its magnetism does depend on various external factors applied like current, no of turns.Diagram of bar magnetDiagram of solenoid

Q: A magnetic dipole is placed in a uniform magnetic fields, B, the potential energy is minimum when dipole is

Potential energy is given by \$U=M.B = -MB cos\, \theta\$ Thus, potential energy is minimum when dipole is parallel to B.

Q: What is a solenoid? Compare the magnetic field produced by a solenoid with the magnetic field of a bar magnet. Draw neat figures and name various components.

A solenoid is a coil of insulated wire wound on a rod-shaped form made of solid iron, solid steel, or powdered iron which produces magnetic field when electric current passed through it. 1) The poles of the bar magnet do not lie exactly on the end of the magnet but is somewhat inside. In solenoid poles can be considered to be lying at the edge.2) The magnetism retains in the bar magnet naturally but in solenoid the magnetism is there so long current flows through it.3) Magnetic field of a bar magnet emanates from throughout the body of the magnet, with more intensity at the poles. While there is no field emanating from the lateral surface of the solenoid.

Q: A vertical bar magnet is dropped from a position on the axis of a fixed metalliccoil as shown in fig - I. In fig - II the magnet is fixed and horizontal coil isdropped. The acceleration of the magnet and coil are a1 and a2 respectivelythen

When a bar magnet is dropped across a current carrying coil, emf is induced in the coil. emf appears as pulses when the bar magnet enters the loop and exits the loop. Induced emf is equal in magnitude to rate of change of magnetic flux but sign of emf is opposite to sign of flux changeif flux increases emf is negative and if the flux decreases then emf is positive. when the bar magnet enters there is a change in magnetic flux across the coil and flux increases hence induced emf is negative. Similarly when the bar magnet its, induce emf is positive. when the bar magnet is fully inside there will not be any flux change and no induced emf in the coilWhen the bar magnet enters emf induced in the coil and creates induced current and induced magnetic field. This induced magnetic field opposes the magnetic filed of bar magnet and reduces the falling speed of bar magnet. Due to this bar magnet entrance will present more time with coil and we get longer pulse. When bar magnet leaves this slowing effect is reduced and speed of falling magnet will be more. Hence at the time of exit the pulse length of induced emf is shorter.

Q: Magnetic dipole moment is a vector quantity directed from:-

Magnetic dipole moment of a bar magnet is a vector and it's direction is from South Pole to North Pole.Hence,option \$A\$ is correct answer.

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REVISE WITH CONCEPTS

Bar Magnet as an Solenoid

ExampleDefinitionsFormulaes

QUICK SUMMARY WITH STORIES

Bar Magnet as an Solenoid

3 mins

Comparing Bar Magnet and Solenoid

2 mins

Important Questions

Force between two identical short bar magnets whose centres are $r$ metre apart is $4.8 N$ when their axes are in the same line. If the separation is increased to $2 r$ metre, the force between them is reduced to

Medium

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A conducing rod $A C$ of length $4 l$ is rotated about a point $O$ in a uniform magnetic field $B$ direction into the paper $A O = l$ and $O C = 3 l$ . Then

Hard

View solution

Write SI unit of magnetic dipole moment.

Medium

View solution

A closely wound solenoid of 800 turns and area of cross section $2.5 \times 1 0^{- 4} m^{2}$ carries a current of $3.0 A$ . Explain the sense in which the solenoid acts like a bar magnet. What is its associated magnetic moment?

Medium

View solution

Distinguish between a bar magnet and a solenoid.

Medium

View solution

Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid . Why?

Easy

View solution

A magnetic dipole is placed in a uniform magnetic fields, B, the potential energy is minimum when dipole is

Medium

View solution

What is a solenoid? Compare the magnetic field produced by a solenoid with the magnetic field of a bar magnet. Draw neat figures and name various components.

Medium

View solution

A vertical bar magnet is dropped from a position on the axis of a fixed metallic
coil as shown in fig - I. In fig - II the magnet is fixed and horizontal coil is
dropped. The acceleration of the magnet and coil are a1 and a2 respectively
then

Medium

View solution

Magnetic dipole moment is a vector quantity directed from:-

Medium

View solution

Bar Magnet as an Equivalent Solenoid

Language

Rate

REVISE WITH CONCEPTS

Bar Magnet as an Solenoid

QUICK SUMMARY WITH STORIES

Bar Magnet as an Solenoid

Comparing Bar Magnet and Solenoid

Force between two identical short bar magnets whose centres are r metre apart is 4.8N when their axes are in the same line. If the separation is increased to 2r metre, the force between them is reduced to

A conducing rod AC of length 4l is rotated about a point O in a uniform magnetic field B direction into the paper AO=l and OC=3l. Then

Write SI unit of magnetic dipole moment.

A closely wound solenoid of 800 turns and area of cross section 2.5×10−4m2 carries a current of 3.0A. Explain the sense in which the solenoid acts like a bar magnet. What is its associated magnetic moment?

Distinguish between a bar magnet and a solenoid.

Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid . Why?

A magnetic dipole is placed in a uniform magnetic fields, B, the potential energy is minimum when dipole is

What is a solenoid? Compare the magnetic field produced by a solenoid with the magnetic field of a bar magnet. Draw neat figures and name various components.

A vertical bar magnet is dropped from a position on the axis of a fixed metallic coil as shown in fig - I. In fig - II the magnet is fixed and horizontal coil is dropped. The acceleration of the magnet and coil are a1 and a2 respectively then

Magnetic dipole moment is a vector quantity directed from:-

Force between two identical short bar magnets whose centres are $r$ metre apart is $4.8 N$ when their axes are in the same line. If the separation is increased to $2 r$ metre, the force between them is reduced to

A conducing rod $A C$ of length $4 l$ is rotated about a point $O$ in a uniform magnetic field $B$ direction into the paper $A O = l$ and $O C = 3 l$ . Then

A closely wound solenoid of 800 turns and area of cross section $2.5 \times 1 0^{- 4} m^{2}$ carries a current of $3.0 A$ . Explain the sense in which the solenoid acts like a bar magnet. What is its associated magnetic moment?

A vertical bar magnet is dropped from a position on the axis of a fixed metallic
coil as shown in fig - I. In fig - II the magnet is fixed and horizontal coil is
dropped. The acceleration of the magnet and coil are a1 and a2 respectively
then