###### Advertisements

###### Advertisements

The electric current flowing in a wire in the direction from B to A is decreasing. Find out the direction of the induced current in the metallic loop kept above the wire as shown.

###### Advertisements

#### Solution

The decreasing magnetic field in the loop due to the decreasing current in wire AB is into the plane of the paper (perpendicular to the plane). So, the direction of the induced current in the loop will be such that it produces an inward magnetic field (perpendicular to the plane). Thus, the current induced in the loop is in clockwise direction (using the right-hand thumb rule)

#### APPEARS IN

#### RELATED QUESTIONS

A circular coil of wire consisting of 100 turns, each of radius 8.0 cm carries a current of 0.40 A. What is the magnitude of the magnetic field B at the centre of the coil?

A long straight wire in the horizontal plane carries a current of 50 A in north to south direction. Give the magnitude and direction of B** **at a point 2.5 m east of the wire.

Magnetic lines of force always cross each other

A circular coil carrying a current I has radius R and number of turns N. If all the three, i.e. the current

I, radius R and number of turns N are doubled, then, the magnetic field at its centre becomes:

(a) Double

(b) Half

(c) Four times

(d) One fourth

Explain the term hysteresis

Obtain an expression for magnetic flux density B at the centre of a circular coil of radius R, having N turns and carrying a current I

Define magnetic lines of force

A circular coil of N turns and radius R carries a current I. It is unwound and rewound to make another coil of radius R/2, current I remaining the same. Calculate the ratio of the magnetic moments of the new coil and original coil.

A charge ‘q’ moving along the X- axis with a velocity `vecv` is subjected to a uniform magnetic field B along the Z-axis as it crosses the origin O.

(i) Trace its trajectory.

(ii) Does the charge gain kinetic energy as it enters the magnetic field? Justify your answer.

The free electrons in a conducting wire are in constant thermal motion. If such a wire, carrying no current, is placed in a magnetic field, is there a magnetic force on each free electron? Is there a magnetic force on the wire?

The net charge in a current-carrying wire is zero. Then, why does a magnetic field exert a force on it?

Which of the following particles will experience maximum magnetic force (magnitude) when projected with the same velocity perpendicular to a magnetic field?

A straight wire carrying an electric current is placed along the axis of a uniformly charged ring. Will there be a magnetic force on the wire if the ring starts rotating about the wire? If yes, in which direction?

Two wires carrying equal currents i each, are placed perpendicular to each other, just avoiding a contact. If one wire is held fixed and the other is free to move under magnetic forces, what kind of motion will result?

A charged particle is moved along a magnetic field line. The magnetic force on the particle is

A straight horizontal wire of mass 10 mg and length 1.0 m carries a current of 2.0 A. What minimum magnetic field *B* should be applied in the region, so that the magnetic force on the wire may balance its weight?

Each of the batteries shown in figure has an emf equal to 5 V. Show that the magnetic field B at the point P is zero for any set of values of the resistances.

Write the expression for the Lorentz force F in vector form.

PQ is a long straight conductor carrying a current of 3A as shown in Figure below. An electron moves with a velocity of 2 x 10^{7} ms^{-1 }parallel to it. Find the force acting on the electron.

**Choose the correct alternative and rewrite the following:**

What will happen to the current passing through a resistance, if the potential difference across it is doubled and the resistance is halved?

**State whether the following statement is true or false:**Magnetic poles exist in pairs.

A charged particle is in motion having initial velocity `vecv` when it enters into a region of uniform magnetic field perpendicular to `vecv`. Because of the magnetic force the kinetic energy of the particle will ______.

An electron is moving with a speed of 3.2 × 10^{7} m/s in a magnetic field of 6.00 × 10^{-4} T perpendicular to its path. What will be the radium of the path? What will be frequency and the energy in keV?

[**Given:** mass of electron = 9.1 × 10^{−31} kg, charge e = 1.6 × 10^{−19} C, 1 eV = 1.6 × 10^{−19} J]

According to the right-hand rule, the direction of magnetic induction if the current is directed in an anticlockwise direction is ______

A conductor has three segments; two straights of length L and a semicircular with radius R. It carries a current I What is the magnetic field B at point P?

The force between two parallel current-carrying conductors is F. If the current in each conductor is doubled, then the force between them becomes ______

What is Lorentz force?

Explain "Magnetic force never does any work on moving charges".

Show that currents in two long, straight, parallel wires exert forces on each other. Derive the expression for the force per unit length on each conductor.

A particle with charge q moves with a velocity v in a direction perpendicular to the directions of uniform electric and magnetic fields, E and B respectively, which are mutually perpendicular to each other. Which one of the following gives the condition for which the particle moves undeflected in its original trajectory?

A charged particle is released from rest in a region of steady and uniform electric and magnetic fields which are parallel to each other. The particle will move in a ____________.

If a particle of charge 10^{12} coulomb moving along the `hat"x" -` direction with a velocity 10^{2} m/s experiences a force of 1 o-s newton in `hat"y" -` direction due to magnetic field, then the minimum magnetic field is ____________.

A proton enters into a magnetic field of induction 1.732 T, with a velocity of 10^{7} m/s at an angle 60° to the field. The force acting on the proton is e = 1.6 × 10^{-19} C, sin 60° = cos 30° = `sqrt3/2`

A particle of charge -16 x 10^{-18} C moving with velocity 10 m/s along the X-axis enters a region where a magnetic field of induction B is along Y-axis and electric field of magnitude 10^{4} V/m is along the negative Z-axis. If the charged particle continues moving along the X-axis, the magnitude of B is ____________.

A very high magnetic field is applied to a stationary charge. Then the charge experiences ______.

The magnetic moment is NOT associated with ____________.

A charged particle enters an environment of a strong and non-uniform magnetic field varying from point to point both in magnitude and direction, and comes out of it following a complicated trajectory. Would its final speed equal the initial speed if it suffered no collisions with the environment?

What is the magnetic induction of the field at the point O in a current I carrying wire that has the shape shown in the figure? The radius of the curved part of the wire is R, the linear parts are assumed to be very long.

A magnetic field exerts no force on

The phenomenon in which a magnetic field is produced in the space near a conductor carrying current is called ______

An infinitely long straight conductor carries a current of 5 A as shown. An electron is moving with a speed of 10^{5} m/s parallel to the conductor. The perpendicular distance between the electron and the conductor is 20 cm at an instant. Calculate the magnitude of the force experienced by the electron at that instant.

In the product `vec"F" = "q" (vec"υ" xx vec"B")`

= `"q" vec"υ" xx ("B"hat"i" +"B"hat"j" + "B"_0hat"k")`

For q = 1 and `vec"υ" = 2hat"i" + 4hat"j" + 6hat"k"` and

`vec"F" = 4hat"i" - 20hat"j" + 12hat"k"`

What will be the complete expression for `vec"B"`?

An infinitely long straight conductor carries a current of 5 A as shown. An electron is moving with a speed of 10^{5} m/s parallel to the conductor. The perpendicular distance between the electron and the conductor is 20 cm at an instant. Calculate the magnitude of the force experienced by the electron at that instant.

In the product

`overset(->)("F") = "q"(overset(->)(υ) xx overset(->)("B"))`

= `"q"overset(->)(υ) xx ("B"overset(^)("i") + "B" overset(^)("j") + "B"_0overset(^)("k"))`

For q = 1 and `overset(->)(υ) = 2overset(^)("i") + 4overset(^)("j") + 6overset(^)("k")` and

`overset(->)("F") = 4overset(^)("i") - 20overset(^)("j") + 12overset(^)("k")`

What will be the complete expression for `overset(->)("B")`?

A cubical region of space is filled with some uniform electric and magnetic fields. An electron enters the cube across one of its faces with velocity v and a positron enters via opposite face with velocity – v. At this instant ______.

- the electric forces on both the particles cause identical accelerations.
- the magnetic forces on both the particles cause equal accelerations.
- both particles gain or loose energy at the same rate.
- the motion of the centre of mass (CM) is determined by B alone.

A charged particle would continue to move with a constant velocity in a region wherein ______.

- E = 0, B ≠ 0.
- E ≠ 0, B ≠ 0.
- E ≠ 0, B = 0.
- E = 0, B = 0.

A charge particle moves along circular path in a uniform magnetic field in a cyclotron. The kinetic energy of the charge particle increases to 4 times its initial value. What will be the ratio of new radius to the original radius of circular path of the charge particle:

At a certain place the angle of dip is 30° and the horizontal component of earth’s magnetic field is 0.5 G. The earth’s total magnetic field (in G), at that certain place, is ______.

Two long current-carrying conductors are placed parallel to each other at a distance of 8 cm between them. The magnitude of the magnetic field produced at the mid-point between the two conductors due to the current flowing in them is 300µT. The equal current flowing in the two conductors is ______.

Two conducting rails are connected to a source of emf and form an incline as shown in figure. A bar of mass 50 g slides without friction down the incline through a vertical magnetic field B. If the length of the bar is 50 cm and a current of 2.5 A is provided by battery. Value of B for which the bar slide at a constant velocity ______ × 10^{-1} Tesla. 2 [g = 10 m/s^{2}]

Figure shows a square loop. 20 cm on each side in the x-y plane with its centre at the origin. The loop carries a current of 7 A. Above it at y = 0, z = 12 cm is an infinitely long wire parallel to the x axis carrying a current of 10 A. The net force on the loop is ______ × 10^{-4} N.

A beam of light travelling along X-axis is described by the electric field E_{y} = 900 sin ω(t - x/c). The ratio of electric force to magnetic force on a charge q moving along Y-axis with a speed of 3 × 10^{7} ms^{-1} will be : [Given speed of light = 3 × 10^{8} ms^{-1}]

A unit vector is represented as `(0.8hat"i" + "b"hat"j" + 0.4hat"k")`. Hence the value of 'b' must be ______.

With a neat labelled diagram, explain cyclotron motion and cyclotron formula.

Distinguish between the forces experienced by a moving charge in a uniform electric field and in a uniform magnetic field. (Any two points)

State the expression for the Lorentz force on a charge due to an electric field as well as a magnetic field. Hence discuss the magnetic force on a charged particle which is (i) moving parallel to the magnetic field and (ii) stationary.

Two long parallel current-carrying conductors are 0.4 m apart in air and carry currents 5 A and 10 A. Calculate the force per metre on each conductor, if the currents are (a) in the same direction and (b) in the opposite direction.

State dimensions of magnetic field.

What is the relation between Tesla and Gauss?

A long straight wire AB carries a current of 5A. P is a proton travelling with a velocity of 2 × 10^{6} m/s, parallel to the wire, 0.2 m from it and in a direction opposite to the current, as shown in Figure below. Calculate the force which magnetic field of the current carrying conductor AB exerts on the proton.

A circular coil of wire is made up of 200 turns, each of radius 10 cm. If a current of 0.5A passes through it, what will be the Magnetic field at the centre of the coil?