An electron having charge 1 . 6 × 10 - 19 C and mass 9 × 10 - 31 kg is moving with 4 × 10 6 m s - 1 speed in a magnetic field 2 × 10 - 1 T in a circular orbit. The force acting on electron and the radius of the circular orbit is _____

1 . 28 × 10 - 13 N , 1 . 1 × 10 - 4 m

12 . 8 × 10 - 13 N , 1 . 1 × 10 - 4 m

1 . 28 × 10 - 14 N , 1 . 1 × 10 - 3 m

1 . 28 × 10 - 13 N , 1 . 1 × 10 - 3 m

HARD

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A uniform electric field $E$ is present horizontally along the paper throughout region but uniform magnetic field $B_{0}$ is present horizontally (perpendicular to plane of paper in inward direction) right to the line $A B$ as shown. A charge particle having charge $q$ and mass $m$ is projected vertically upward and crosses the line $A B$ after time $t_{0}$ . The speed of projection if particle moves after $t_{0}$ with constant velocity. (given $q E = m g$ ) is $n t_{0} .$ Find the value of ' $n$ ' $(g = 9.8 {ms}^{- 2})$

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Important Questions on Moving Charges and Magnetism

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

An electron and a proton enter a magnetic field perpendicularly both have same kinetic energy. Which of the following is true?

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

Proton with kinetic energy of

1 M e V

moves from south to north. It gets an acceleration of

10^{12} m s^{- 2}

by an applied magnetic field (west to east). The value of magnetic field: (Rest mass of proton is

1.6 \times 10^{- 27} k g

)

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

A positive charge

q

is projected in magnetic field of width

\frac{m v}{\sqrt{2} q B}

with velocity

v

. Then, the time taken by charged particle to emerge from the magnetic field is

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

One can define an alpha-volt

(α - V)

to be the energy acquired by an

α

-particle when it is accelerated by a potential of

1 V

. For this problem, you may take a proton to be

2000

times heavier than an electron. Then,

HARD

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

A charged particle is introduced at the origin

x = 0, y = 0, z = 0

with a given initial velocity

\vec{v}

. A uniform electric field

\vec{E}

and a uniform magnetic field

\vec{B}

exist everywhere. The velocity

\vec{v}

, electric field

\vec{E}

and a uniform magnetic field

\vec{B}

are given in the columns below

Column 1	Column 2	Column 3
1. Electron with $\vec{v} = 2 \frac{E_{0}}{B_{0}} \hat{x}$	(i) $\vec{E} = E_{0} \hat{z}$	(P) $\vec{B} = - B_{0} \hat{x}$
2. Electron with $\vec{v} = \frac{E_{0}}{B_{0}} \hat{y}$	(ii) $\vec{E} = - E_{0} \hat{y}$	(Q) $\vec{B} = B_{0} \hat{x}$
3.Proton with $\vec{v} = 0$	(iii) $\vec{E} = {- E}_{0} \hat{x}$	(R) $\vec{B} = B_{0} \hat{y}$
4. Proton with $\vec{v} = 2 \frac{E_{0}}{B_{0}} \hat{x}$	(iv) $\vec{E} = E_{0} \hat{x}$	(S) $\vec{B} = B_{0} \hat{z}$

In which case will the particle describe a helical path with axis along positive z direction?

HARD

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

When a proton of charge

e

and mass

m

is released from rest in a room, it starts to move with initial uniform acceleration

a_{0}

towards West. When it is projected towards North with a speed

v_{0}

, it moves with an initial acceleration

3 a_{0}

towards West. The electric and magnetic fields in the room are respectively

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

A particle of mass

m

and charge

q

has an initial velocity

\vec{v} = v_{0} \hat{j}

. If an electric field

\vec{E} = E_{0} \hat{i}

and magnetic field

\vec{B} = B_{0} \hat{i}

act on the particle, its speed will double after a time

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

A proton and an

α

-particle are projected with the same kinetic energy at right angles to a uniform magnetic field. The ratio of the radii of their paths is

HARD

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

A charged particle is introduced at the origin

x = 0, y = 0, z = 0

with a given initial velocity

\vec{v}

. A uniform electric field

\vec{E}

and a uniform magnetic field

\vec{B}

exist everywhere. The velocity

\vec{v}

, electric field

\vec{E}

and a uniform magnetic field

\vec{B}

are given in the columns below

Column 1	Column 2	Column 3
1. Electron with $\vec{v} = 2 \frac{E_{0}}{B_{0}} \hat{x}$	(i) $\vec{E} = E_{0} \hat{z}$	(P) $\vec{B} = - B_{0} \hat{x}$
2. Electron with $\vec{v} = \frac{E_{0}}{B_{0}} \hat{y}$	(ii) $\vec{E} = - E_{0} \hat{y}$	(Q) $\vec{B} = B_{0} \hat{x}$
3.Proton with $\vec{v} = 0$	(iii) $\vec{E} = {- E}_{0} \hat{x}$	(R) $\vec{B} = B_{0} \hat{y}$
4. Proton with $\vec{v} = 2 \frac{E_{0}}{B_{0}} \hat{x}$	(iv) $\vec{E} = E_{0} \hat{x}$	(S) $\vec{B} = B_{0} \hat{z}$

In which case would the particle move in a straight line along the negative direction of y axis

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

α

-particle consists of

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

A charge

q

is accelerated through a potential difference

V

. It is then passed normally through a uniform magnetic field, where it moves in a circle of radius

r

. The potential difference required to move it in a circle of radius

2 r

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

A negative test charge is moving near a long straight wire carrying a current. The force acting on the test charge is parallel to the direction of the current. The motion of the charge is:

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

An electron is moving in a circle of radius

r

in a uniform magnetic field

B

. Suddenly, the field is reduced to

\frac{B}{2}

. The radius of the circular path now becomes

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

An electron having charge

1.6 \times 10^{- 19} C

and mass

9 \times 10^{- 31} kg

is moving with

4 \times 10^{6} m s^{- 1}

speed in a magnetic field

2 \times 10^{- 1} T

in a circular orbit. The force acting on electron and the radius of the circular orbit is _____

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

Cathode rays enter into a uniform magnetic field perpendicular to the direction of magnetic field. In the magnetic field, their path will be

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

Question Image

In the above diagram, a particle of mass $' m'$ and charge $' q'$ initially moving along - axis with velocity $v_{x}$ enters the region between the two charged plates The length of the plate system is $L$ and a uniform electric field between the plate is $E$ Find the vertical deflection of the particle at the far edge of the plate?

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

A proton is moving perpendicular to a uniform magnetic field of

2.5

T

with

2 MeV

kinetic energy. The force on proton is ______

N

. (Mass of proton

= 1.6 \times 10^{- 27} kg

, Charge of proton

= 1.6 \times 10^{- 19} C

)

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

A proton, an electron, and a Helium nucleus, have the same energy. They are in circular orbits in a plane due to magnetic field perpendicular to the plane. Let

r_{p}, r_{e}

and

r_{H e}

be their respective radii, then,

HARD

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

A charged particle is introduced at the origin

x = 0, y = 0, z = 0

with a given initial velocity

\vec{v}

. A uniform electric field

\vec{E}

and a uniform magnetic field

\vec{B}

exist everywhere. The velocity

\vec{v}

, electric field

\vec{E}

and a uniform magnetic field

\vec{B}

are given in the columns below

Column 1	Column 2	Column 3
1. Electron with $\vec{v} = 2 \frac{E_{0}}{B_{0}} \hat{x}$	(i) $\vec{E} = E_{0} \hat{z}$	(P) $\vec{B} = - B_{0} \hat{x}$
2. Electron with $\vec{v} = \frac{E_{0}}{B_{0}} \hat{y}$	(ii) $\vec{E} = - E_{0} \hat{y}$	(Q) $\vec{B} = B_{0} \hat{x}$
3.Proton with $\vec{v} = 0$	(iii) $\vec{E} = {- E}_{0} \hat{x}$	(R) $\vec{B} = B_{0} \hat{y}$
4. Proton with $\vec{v} = 2 \frac{E_{0}}{B_{0}} \hat{x}$	(iv) $\vec{E} = E_{0} \hat{x}$	(S) $\vec{B} = B_{0} \hat{z}$

In which case will the particle move in a straight line with a constant velocity?

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Motion in a Magnetic Field

An electron is moving in a circular path under the influence of a transverse magnetic field of

3.57 \times 10^{- 2} T

. If, the value of

\frac{e}{m}

1 .76 \times 10^{11} C {kg}^{- 1}

, the frequency of revolution of the electron is

Important Questions on Moving Charges and Magnetism

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