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

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

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Important Questions on Moving Charges and Magnetism

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

Ionized hydrogen atoms and

α

-particles with same momenta enters perpendicular to a constant magnetic field

B

. The ratio of their radii of their paths

r_{H} : r_{α}

will be

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

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?

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

EASY

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

A proton and an alpha particle both enter a region of uniform magnetic field B, moving at right angles to the field B. if the radius of circular orbits for both the particles is equal and the kinetic energy acquired by proton is 1 MeV, the energy acquired by the alpha particle will be:

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

)

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?

HARD

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

Two parallel metal plates $A$ and $B$ separated by a distance $25 cm$ are connected to an ammeter. Photons of energy $3.28 eV$ are incident on the photosensitive plate $A$ of threshold wavelength $5000 \overset{o}{A}$ . The minimum value of the magnetic field to be applied parallel to the plates so that the current through the ammeter becomes zero is $B \times 10^{- 5} T$ . Then the value of

$B$ is (mass of electron $= 9.0 \times 10^{- 31} kg$ , charge of electron $= 1.6 \times 10^{- 19} C$ )

EASY

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

An electron is moving with a velocity

2 \times 10^{6} m / s

along positive

x

-direction in the uniform electric field of

8 \times 10^{7} V / m

applied along positive

y

-direction. The magnitude and direction of a uniform magnetic field (in tesla) that will cause the electrons to move undeviated along its original path is

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

A beam of protons with speed

4 \times 10^{5} m s^{- 1}

enters a uniform magnetic field of

0.3 T

at an angle

60 °

to the magnetic field, the pitch of the resulting helical path of protons is close to : (Mass of the proton

= 1.67 \times 10^{- 27} kg

, charge of the proton

= 1.69 \times 10^{- 19} C

)

MEDIUM

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

A rectangular region of dimensions $w \times I (w < < I)$ has a constant magnetic field into the plane of the paper as shown. On one side the region is bounded by a screen. On the other side positive ions of mass $m$ and charge $q$ are accelerated from rest and towards the screen by a parallel plate capacitor at constant potential difference $V < 0$ , and come out through a small hole in the upper plate. Which one of the following statements is correct regarding the charge on the ions that hit the screen?

Question Image

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

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,

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 _____

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 proton accelerated by a potential difference

500 kV

flies through a uniform transverse magnetic field

0.1 T

. The field is spread on a region of

1.0 cm

thickness. The angle through which the proton gets deviated from its original direction is (Proton mass

= 1.6 \times 10^{- 27} kg

and charge of proton

= 1.6 \times 10^{- 19} C

)

MEDIUM

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

An electron, a proton and an alpha particle having the same kinetic energy are moving in circular orbits of radii

r_{e}, r_{p}, r_{α}

respectively in a uniform magnetic field B. The relation between

r_{e}, r_{p}, r_{α}

is:

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

MEDIUM

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

A proton and an

α

- particle (with their masses in the ratio of

1 : 4

and charges in the ratio of

1 : 2

) are accelerated from rest through a potential difference

V .

If a uniform magnetic field

(B)

is set up perpendicular to their velocities, the ratio of the radii

r_{p} : r_{α}

of the circular paths described by them will be:

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

Important Questions on Moving Charges and Magnetism

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