The earth's magnetic field is due to electrical currents produced by convective motion of metallic fluids (molten iron and nickel) in the outer core of the earth.This effect is known as
cyclotron
dynamo
inductive
solenoid

Assertion (A): The earth's magnetic field is due to iron present in its core. Reason (R ): At a high tempeature magnet losses its magnetic property or magnetism.

The Betatron was the first important machine for producing high energy electrons. The action of the betatron depends on the same fundamental principle as that of the transformer in which an alternating current applied to a primary coil induces an altermating current usually with higher or lower voltage in the secondary coil. In the betatron secondary coil is replaced by a doughnut shaped vacuum chamber.Electron produced in the doughnut from a hot filament, are given a preliminary acceleration by the application of an electric field having potential difference of 20 kV to 70 kV , when an alternating magnetic field is applied parallel to the axis of the tube, two effects are produced (1) an electromotive force is produced in the electron orbit by the changing magnetic flux that gives an additional energy to the electrons (2) a radial force is produced by the action of magnetic field whose direction is perpendicular to the electron velocity. Which keeps the electron moving in a circular path. Conditions are arranged such that the increasing magnetic field keeps the electron in a circular orbit of constant radius. The mathematical relation between the betatron parameters to ensure the above condition is called BETATRON condition. If the orbit radius of the circular path traced by the electron is R , magnetic field is B , speed of the electron is v , mass of the electron is m , charge on the electron is e and phi is the flux within the orbit of radius R . Then answer the following questions based on the above comprehension. What is the value of (d(m|vecv|))/(dt) ?

The Betatron was the first important machine for producing high energy electrons. The action of the betatron depends on the same fundamental principle as that of the transformer in which an alternating current applied to a primary coil induces an altermating current usually with higher or lower voltage in the secondary coil. In the betatron secondary coil is replaced by a doughnut shaped vacuum chamber.Electron produced in the doughnut from a hot filament, are given a preliminary acceleration by the application of an electric field having potential difference of 20 kV to 70 kV , when an alternating magnetic field is applied parallel to the axis of the tube, two effects are produced (1) an electromotive force is produced in the electron orbit by the changing magnetic flux that gives an additional energy to the electrons (2) a radial force is produced by the action of magnetic field whose direction is perpendicular to the electron velocity. Which keeps the electron moving in a circular path. Conditions are arranged such that the increasing magnetic field keeps the electron in a circular orbit of constant radius. The mathematical relation between the betatron parameters to ensure the above condition is called BETATRON condition. If the orbit radius of the circular path traced by the electron is R , magnetic field is B , speed of the electron is v , mass of the electron is m , charge on the electron is e and phi is the flux within the orbit of radius R . Then answer the following questions based on the above comprehension. What is the tangential force acting on the electron ?

The Betatron was the first important machine for producing high energy electrons. The action of the betatron depends on the same fundamental principle as that of the transformer in which an alternating current applied to a primary coil induces an altermating current usually with higher or lower voltage in the secondary coil. In the betatron secondary coil is replaced by a doughnut shaped vacuum chamber.Electron produced in the doughnut from a hot filament, are given a preliminary acceleration by the application of an electric field having potential difference of 20 kV to 70 kV , when an alternating magnetic field is applied parallel to the axis of the tube, two effects are produced (1) an electromotive force is produced in the electron orbit by the changing magnetic flux that gives an additional energy to the electrons (2) a radial force is produced by the action of magnetic field whose direction is perpendicular to the electron velocity. Which keeps the electron moving in a circular path. Conditions are arranged such that the increasing magnetic field keeps the electron in a circular orbit of constant radius. The mathematical relation between the betatron parameters to ensure the above condition is called BETATRON condition. If the orbit radius of the circular path traced by the electron is R , magnetic field is B , speed of the electron is v , mass of the electron is m , charge on the electron is e and phi is the flux within the orbit of radius R . Then answer the following questions based on the above comprehension. What is the BETATRON condition ?

A: The earth's magnetic field not only varies from point to point in space, it also changes with time R: The earth's core is known to contain iron yet geologists do not regard this as a source of the earth's magnetism.

The phenomena of electromagnetic induction is: (a) the process of charging a body. (b) the process of generating magnetic field due to a current passing through a coil. (c) producing induced current in a coil due to relative motion between a magnet and the coil. (d) the process of rotating a coil of an electric motor.

A currrent I is passed through a silver strip of width d and area of cross section A. The number of free electrons per unit volume is n. (a) Find the drift velocity v of the electrons. (b) If a magnetic field B exists in the region as shown in what is the average magnetic force on the free electrons? (c) Due to the magnetic force, the free electrons get accumulated on one side of the conductor along its length. This produces a transverse electric field in the conductor which opposes the magnetic force on the electrons. Find the magnitude of the electric field which will be the potential diference developed across the width of the conductor due to the electron- accumulation? The appearance of a transverse emf, when a current-carrying wire is placed in a magnetic field, is called hall effect.

A long straight horizontal cable carries a current of 2.5amp . In the direction 10^@ south of west to 10^@ north of east, figure. The magnetic meridian of the place happens to be 10^@ west of the geographic meridian. The earth's magnetic field at the location is 0.33G and the angle of dip is zero. Locate the line of neutral points (Ignore the thickness of the cable). [At neutral points, magnetic fied due to a current cable is equal and opposite to the horizontal component of earth's magnetic field.]

A fan operates at 200 volt (DC) consuming 1000W when running at full speed . It's internal wiring has resistance 1 Omega . When the fan runs at full speed , its speed becomes constant. This is because the torque due to magnetic field inside tha fan is balanced by the torque due to air resistance on the blades of the fan and torque due to friction between the fixed part and the shaft of the fan. The electrical power going into the fan is spent (i) in the internal resistance as heat, call it P_(1)(ii) in doing work against internal friction and air resistance producing heat, sound etc. call it P_(2) . When the coil of fan rotates, an emf is also induced in the coil. This opposes the external emf applied to snd the current into the fan. This emf is called back-emf,call it 'e' . Answer the following questions when the fan is running at full speed. The value of power P_(2) si

A fan operates at 200 volt (DC) consuming 1000W when running at full speed . It's internal wiring has resistance 1 Omega . When the fan runs at full speed , its speed becomes constant. This is because the torque due to magnetic field inside tha fan is balanced by the torque due to air resistance on the blades of the fan and torque due to friction between the fixed part and the shaft of the fan. The electrical power going into the fan is spent (i) in the internal resistance as heat, call it P_(1)(ii) in doing work against internal friction and air resistance producing heat, sound etc. call it P_(2) . When the coil of fan rotates, an emf is also induced in the coil. This opposes the external emf applied to snd the current into the fan. This emf is called back-emf,call it 'e' . Answer the following questions when the fan is running at full speed. The value of power P_(1) is