Magnetic Effects of Current and Magnetism

A beam of electron passes undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move

A closely wound solenoid of 2000 turns and area of cross-section 1.5 x 10⁻⁴ m² carries a current of 2.0 A. It suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field 5 x 10⁻² tesla making an angle of 30 with the axis of the solenoid. The torque on the solenoid will be:

A charged particle (charge q) is moving in a circle of radius R with uniform speed v. The associated magnetic moment µ is given by

A bar magnet having a magnetic moment of 2 x 10⁴ JT⁻¹ is free to rotate in a horizontal plane. A horizontal magnetic field B = 6 x 10⁻⁴ T exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction 60⁰ from the field is

A bar magnet of magnetic moment M is placed at right angles to a magnetic induction B. If a force F is experienced by each pole of the magnet, the length of the magnet will be

A circular disc of radius 0.2 meter is placed in a uniform magnetic field of induction 1/π (Wb / m²) in such a way that its axis makes an angle of 60⁰ with B⃗. The magnetic flux linked with the disc is:

If two electric bulbs have 40 W and 60 W ratings at 220 V, then the ratio of their resistances will be

Tangent galvanometer is used to measure

Before using the tangent galvanometer, its coil is set in

An electron is moving in a circular path under the influence of a transverse magnetic field of 3.57 x 10⁻² T. If the value of e/m is 1.76 x 10¹¹ C/kg, the frequency of revolution of the electron is

A proton is projected with a speed of 3 x 10⁶ m/s horizontally from east to west. An uniform magnetic field of strength 2 x 10⁻³ T exist in the vertically upward direction. What would be the acceleration of proton?

The magnetic field at the centre of a circular coil carrying current I ampere is B. If the coil is bent into smaller circular coil of n turns, then its magnetic field at the centre is B’. The ratio between B’ and B is

For a thermocouple, the neutral temperature is 270⁰C when its cold junction is at 20⁰C. What will be the neutral temperature and the temperature of inversion when the temperature of the cold junction is increased to 40⁰C?

The magnetic susceptibility does not depend upon the temperature in

If r be the distance of a point on the axis of a magnetic dipole from its centre then the magnetic field at such a point is proportional to

The effective length of magnet is 31.4 cm and its pole strength is 0.8 Am. The magnetic moment, if it is bent in the form of a semicircle is ……… A-m²

At place on earth, the vertical component of earth’s magnetic field is √3 times its horizontal component. The angle of dip at this place is …….

A tangent galvanometer has a coil of 50 turns and a radius of 20 cm. The horizontal component of earth’s magnetic field is Bʜ=3×10⁻⁵ T. What will be the current which gives a deflection of 45⁰?

Identify the paramagnetic substance

Equal currents are passing through two very long and straight parallel wires in the same direction. They will

Core of electromagnets are made of ferromagnetic material which has

The dimensions of magnetic field intensity B are

If the magnetising field on a ferromagnetic material is increased, its permeability

Two particles A and B having equal charges, after being accelerated through the same potential difference enter into a region of uniform magnetic field and the particles describe circular paths of radii R₁ and R₂, respectively. The ratio of the masses of A and B is

Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show

Magnetism of a magnet is due to

There is a ring of radius r having linear charge density λ and rotating with a uniform angular velocity ω. The magnetic field produced by this ring at its own centre would be

Curie temperature is the temperature above which

A freely suspended bar magnet aligns itself in

A proton beam enters a magnetic field of 10⁻⁴ Wb/m² normally. If the specific charge of the proton is 10¹¹ C/kg and its velocity is 10⁹ m/s, then the radius of the circle described will be

A susceptibility of a certain magnetic material is 400. What is the class of the magnetic material?

If a magnetic substance is brought near the north or the south pole of a bar magnet, it is:

A cyclotron is used to accelerate

A paramagnetic sample shows a net magnetisation of 0.8 Am⁻¹, when placed in an external magnetic field of strength 0.8 T at a temperature 5K. When the same sample is placed in an external magnetic field of 0.4 T at a temperature of 20K. The magnetisation is

The value of workdone for rotating a magnet of magnetic moment M by an angle θ in external magnetic field H is given by

A vibration magnetometer placed in magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of 2 sec in earth’s horizontal magnetic field of 24 microtesla. When a horizontal field of 18 microtesla is produced opposite to the earth’s field by placing a current carrying wire, the new time period of magnet will be

Two parallel beams of positron moving in the same direction will

The intensity of magnetisation of a bar magnet is 5 x 10⁴ Am⁻¹. The magnetic length and the area if cross- section of the magnet are 12 cm and 1 cm⁻² respectively. The magnitude of magnetic moment of this bar magnet (in SI unit) is

Two concentric coils each of radius equal to 2π cm are placed at right angles to each other. If 3A and 4A are the currents flowing through the two coils, respectively. The magnetic induction (in Wb/m²) at the centre of the coils will be

The conducting loop in the form of a circle is placed in a uniform magnetic field with its plane perpendicular to the direction of the field. An emf will be induced in the loop,if

The magnetic susceptibility of a material of a rod is 299. Permeability of vacuum μ₀ is 4π x 10⁻⁷ Hm⁻¹. Absolute permeability of the material of the rod is

The magnetic moment of a diamagnetic atom is

A solenoid has length 0.4 cm, radius 1 cm and 400 turns of wire. If a current of 5 A is passed through this solenoid, then what is the magnetic field inside the solenoid?

A thermoelectric refrigerator works on

Two poles of same strength attract each other with a force of magnitude F when placed at the two corners of an equilateral triangle. If a north pole of same strength is placed at the third vertex, it experiences a force of magnitude equal to

There are four light-weight-rod samples A,B,C,D separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted
(i) A is feebly repelled
(ii) B is feebly attracted
(iii) C is strongly attracted
(iv) D remains unaffected
Which one of the following is true?

A toroid having 200 turns caries a current of 1 A. The average radius of the toroid is 10 cm. The magnetic field at any point in the open space inside the toroid is

A short bar magnet of magnetic moment 0.4 JT⁻¹ is placed in a uniform magnetic field of 0.16 T. The magnet is in stable equilibrium when the potential energy is

The magnetic susceptibility is negative for

A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole It:

The horizontal and vertical components of earth’s magnetic field at a place are 0.3 G and 0.52 G. The earth’s magnetic field and the angle of dip are

The magnetic field due to a current carrying circular loop of radius 3 cm at a point on the axis at a distance of 4 cm from the centre is 54 μT. What will be its value at the centre of the loop?

Two lines of force due to a bar magnet

A magnetic needle suspended parallel to a magnetic field requires √3 J of work to turn it through 60⁰. The torque needed to maintain the needle in this position will be:

A proton of mass m and charge q is moving in a plane with kinetic energy E. If there exists a uniform magnetic field B, perpendicular to the plane motion, the proton will move in a circular path of radius

A short magnet of magnetic moment M, is placed on a straight line. The ratio of magnetic induction fields B₁, B₂, B₃ values on this line at points which are at distance 30 cm, 60 cm and 90 cm respectively from the centre of the magnet is

A small rod of bismuth is suspended freely between the poles of a strong electromagnet. It is found to arrange itself at right angles to the magnetic field. This observation established that bismuth is

If the velocity of charged particle has both perpendicular and parallel components while moving through a magnetic field, then what is the path followed by a charged particle?

A particle with charge q is moving along a circle of radius R with uniform speed v. The associated magnetic moment μ is given by

On heating a ferromagnetic substance above curie temperature

The workdone in turning a magnet of magnetic moment M by an angle of 90⁰ from the magnetic meridian is n times the corresponding work done to turn it through an angle of 60⁰. The value of n is

A dip needle vibrates in a vertical plane perpendicular to magnetic meridian. The time of vibration is found to be 25, the same needle is then allowed to vibrate in the horizontal plane and the time period is again found to be 25. Then, the angle of dip is

Magnetic induction produced at the centre of a circular loop carrying current is B. The magnetic moment of the loop of radius R is (where, μ₀ = permeability of free space)

If the dipole moment of a short bar magnet is 1.25 A-m², the magnetic field on its axis at a distance of 0.5 m from the centre of the magnet is

In cyclotron, for a given magnet, radius of the semicircle traced by positive ion is directly proportional to (where, v=velocity of positive ion)

The horizontal component of earth’s magnetic field at a place is 3 x 10⁻⁴ T and the dip is tan⁻¹ (4/3). A metal rod of length 0.25 m is placed in N-S direction and is moved at a constant speed of 10 cms⁻¹ towards the east. The emf induced in the rod will be

when a magnetic field is applied on a stationary electron, then it

An electron in a circular orbit of radius 0.05 nm performs 10¹⁶ rev/s. The magnetic moment due to this rotation of electron is (in A-m²)

Electromagnets are made of soft iron because soft iron has

Two 220V – 100W bulbs are connected first in series and then in parallel. Each time the combination is connected to 220 V AC supply line. The powers drawn by the combination in each case respectively will be

If a magnet is suspended at an angle 30⁰ to the magnetic meridian, the dip needle makes angle of 45⁰ with the horizontal. The real dip is

If a steel wire of length l and magnetic moment M is bent into a semicircular arc, then the new magnetic moment is

Two thin long conductors separated by a distance d carry currents I₁ and I₂ in the same direction. They exert a force F on each other. Now, the current in one of them is increased to two times and its direction is reversed. The distance is also increased to 3d. The new value of force between them is

An iron rod of volume 10⁻⁴ m³ and relative permeability 1000 is placed inside a long solenoid having 5 turns/cm. If a current of 0.5 A is passed through the solenoid, then the magnetic moment of the rod is

The ultimate individual unit of magnetism in any magnet is called

The ratio of magnetic dipole moment of an electron of charge e and mass m in Bohr’s orbit in hydrogen atom to its angular momentum is

A wire of length L metre carrying a current I ampere is bent in the form of a circle. The magnitude of th magnetic moment is

The ferromagnetic substance is

Which of the following, is a vector quantity?

If a proton, a deuteron and an alpha particle, on being accelerated by the same potential difference, enter perpendicularly to a magnetic field. The ratio of their respective kinetic energies is

A proton and helium nucleus are shot into a magnetic field at right angles to the field with same kinetic energy. Then, the ratio of their radii is

Time period of oscillation of a magnet is 2 sec. When it is remagnetised so that its pole strength is 4 times, its period will be

Two charged particles have charges and masses in the ratio 2:3 and 1:4 respectively. If they enter a uniform magnetic field and move with the same velocity, then the ratio of their respective time periods of revolution is

A metal rod of length l cuts across a uniform magnetic field B with a velocity v. If the resistance of the circuit of which the rod forms a part is r, then the force required to move the rod is

A current of 2 A is made to flow through a coil which has only one turn. The magnetic field produced at the centre is 4πx10⁻⁶ Wb/m². The radius of the coil is

In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular path of radius R using a magnetic field B. If V and B are kept constant, the ratio ( charge on the ion / mass of the ion) will be proportional to

A long straight wire is carrying a current of 12 A. The magnetic field at a distance of 8 cm is (μ₀=4π x 10⁻⁷ N A²)

A wire in the form of a circular loop of one turn, carrying a current, produces a magnetic field B at the centre. If the same wire is looped into a coil of two turns and carries the same current, the new value of magnetic induction at the centre is

In a tangent galvanometer, a current of 0.1 A produces a deflection of 30⁰. The current required to produce a deflection of 60⁰ is

The magnetic field at a point on the axis of a long solenoid having 5 turns per cm length when a current of 0.8 A flows through it is

A long straight wire carrying current of 30A is placed in an external uniform magnetic field of induction 4 x 10⁻⁴ T. The magnetic field is acting parallel to the direction of the current. The magnitude of resultant magnetic induction in tesla at a point 2.0 cm away from the wire is

The magnetic lines of force inside a bar magnet

A particle of mass m, charge Q and kinetic energy T enters a transverse uniform magnetic field of induction B⃗. After 3 seconds, the kinetic energy of the particle will be:

Two straight wires each 10 cm long are parallel to one another and seperated by 2 cm. When the current flowing in them is 30A and 40 A respectively, then the force experienced by either of the wires is

A wire of one metre length carries a constant current. The wire is bent to form a circular loop. The magnetic field at the centre of this loop is B.The same is now bent to form a circular loop of smaller radius having four turns. The magnetic field at the centre of this new loop will be

When three identical bulbs of 60 W-200 V rating are connected in series to a 200 V supply, the power drawn by them will be

A magnetic force acting on a charged particle of charge -2µC in a magnetic field of 2T acting in y direction, when the particle velocity is (2i + 3j) x 10⁶ m/s, is

A proton is moving in a uniform magnetic field B in a circular path of radius a in a direction perpendicular to Z-axis along which field B exists. Calculate the angular momentum. If the radius is a and charge on proton is e.

The magnetic field in a certain region of space is given by B =8.35 x 10⁻² Î T. A proton is shot into the field with velocity v=(2 x 10⁵i ̂ + 4 x 10⁵ j ̂ ) m/s. The proton follows a helical path in the field. The distance moved by proton in the x-direction during the period of one revolution in the yz- plane will be (mass of proton=1.67 x 10⁻²⁷ kg)

Unit of reduction factor is

A thin ring of radius R meter has charge q coulomb uniformly spread on it. The ring rotates about its axis with a constant frequency of f revolutions/s. The value of magnetic induction in Wb/m² at the centre of the ring is

A planar coil having 12 turns carries 15 A current. The coil is oriented with respect to the uniform magnetic field B = 0.2 Î T such that its directed area is A = 0.04 Îm². The potential energy of the coil in the given orientation is

A galvanometer has a coil of resistance 100 ohm and gives a full-scale deflection for 30 mA current. It is to work as a voltmeter of 30 volt range, the resistance required be added will be

Two parallel long wires carry currents i₁ and i₂ with i₁ > i₂ . When the currents are in the same direction, then the magnetic field midway between the wires is 10μT. When the direction of i₂ is reversed, then it becomes 40μT. Then, ratio of i₁/ i₂ is

A particle having a mass of 10⁻² kg carries a charge of 5 x 10⁻⁸C. The particle is given an initial horizontal velocity of 10⁵ m/s. In the presence of electric field E and magnetic field B. To keep the particle moving in a horizontal direction, it is necessary that
(1) B should be perpendicular to the direction of velocity and E should be along the direction of velocity.
(2) Both B and E should be along the direction of velocity.
(3) Both B and E are mutually perpendicular and perpendicular to the d

A thermally insulated rigid container contains an ideal gas heated by a filament of resistance 100 ohm through a current of 1 A for 5 min, then change in internal energy is

When an electron beam passes through an electric field they gain kinetic energy. lf the same electron beam passes through a magnetic field, then their

Sound production from tape recorder makes use of

A uniform electric field and uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron

Magnetic susceptibility of a material is given as

Graph of force per unit length between two long parallel current carrying conductors and the distance between them is

Weber/m² is equal to

Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency f Hz. The magnitude of magnetic induction at the centre of the ring is

The direction of magnetic line of force of a bar magnet is

An alternating electric field, of frequency v, is applied across the dees (radius = R) of a cyclotron that is being used to accelerate protons (mass = m). The operating magnetic field (B) used in the cyclotron and the kinetic energy (K) of the proton beam, produced by it, are given by:

Curie temperature above which

A proton carrying 1 MeV kinetic energy is moving in a circular path of radius R in uniform magnetic field. What should be the energy of an α-particle to describe a circle of same radius in the same field?

An electron moving in a uniform magnetic field of induction of intensity B, has its radius directly proportional to

A long straight wire carries a certain current and produces a magnetic field of 2 x 10⁻⁴ weber/m² at a perpendicular distance of 5 cm from the wire. An electron situated at 5 cm from the wire moves with a velocity 10⁷ m/s towards the wire along perpendicular to it. The force experienced by the electron will be (charge on electron = 1.6 x 10⁻¹⁹C)

A galvanometer is converted into an ammeter by connecting

Two bulbs 40 watt and 60 watt and rated voltage 240 V are connected in series across a potential difference of 420 V. Which bulb will work at above its rated voltage

A disc of radius 0.1 m is rotating with a frequency 10 rev/sec in a normal magnetic field of strength 0.1 tesla. Net induced emf is

An electric kettle has two heating elements. One brings it to boil in ten minutes and the other in fifteen minutes. If two heating filaments are connected in parallel, the water in kettle will boil in

A steady current of 1.5 amp flows through a copper voltmeter for 10 mins. If the electrochemical equivalent of copper is 30 x 10⁻⁵ g/coulomb, the mass of copper deposited on the electrode will be

The resistance of an ammeter is 13 Ω and its scale is graduated for a current upto 100 amps. After an additional shunt has been connected to this ammeter it becomes possible to measure currents upto 750 amperes by this meter. The value of shunt resistance is

A current I flows along the length of an infinitely long, straight, thin walled pipe. Then

A particle of mass m, charge Q and kinetic energy T enters a transverse uniform magnetic field of induction B⃗ . After 3 seconds the kinetic energy of the particle will be

The oscillating frequency of a cyclotron is 10 MHz. If the radius of its Dees is o.5 m, the kinetic energy of a proton, which is accelerated by the cyclotron is

An electric kettle takes 4A current at 220 V. How much time will it take to boil 1 kg of water from temperature 20⁰C? The temperature of boiling water is 100⁰C