Lorentz Force

When a charged particle with velocity is subjected to an induction magnetic field the force on it is non-zero. What does this imply?

1.	Angle between and is necessarily .
2.	Angle between and can have any value other than .
3.	Angle between and can have any value other than zero and .
4.	Angle between and is either zero or .

Under the influence of a uniform magnetic field a charged particle is moving in a circle of radius R with constant speed v. The time period of the motion:

1. depends on v and not on R.

2. depends on both R and v.

3. is independent of both R and v.

4. Depends on R and not on v.

In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential and then made to describe semi-circular paths of radius using a magnetic field . If and are kept constant, the ratio of will be proportional to:
1.
2.
3.
4.

A beam of electrons passes un-deflected through mutually perpendicular electric and magnetic fields. Where do the electrons move if the electric field is switched off and the same magnetic field is maintained?

1.	in an elliptical orbit.
2.	in a circular orbit.
3.	along a parabolic path.
4.	along a straight line.

A particle of mass charge and kinetic energy enters a transverse uniform magnetic field of induction What will be the kinetic energy of the particle after seconds?

1.		2.
3.		4.

Under the influence of a uniform magnetic field, a charged particle moves with constant speed in a circle of radius The time period of rotation of the particle:

1.	depends on and not on
2.	depends on R and not on
3.	is independent of both and
4.	depends on both and

A beam of cathode rays is subjected to cross Electric (E) and magnetic fields(B). The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by:

1. $\frac{B^2}{2V{E}^2}$

2. $\frac{2V{B}^2}{E^2}$

3. $\frac{\mathrm{2V}{E}^2}{B^2}$

4. $\frac{E^2}{2V{B}^2}$

(where V is the potential difference between cathode and anode)

A uniform electric field and a uniform magnetic field are acting in 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:

1.	speed will decrease
2.	speed will increase
3.	will turn towards the left of the direction of motion
4.	will turn towards the right of the direction of motion

When a proton is released from rest in a room, it starts with an initial acceleration towards the east. When it is projected towards the north with a speed of , it moves with an initial acceleration of towards the east. What are the electric and magnetic fields in the room?

1.
2.
3.
4.

Moving perpendicular to field , a proton and an alpha particle both enter an area of uniform magnetic field . If the kinetic energy of the proton is and the radius of the circular orbits for both particles is equal, the energy of the alpha particle will be:
1.
2.
3.
4.

An electron is moving in a circular path under the influence of a transverse magnetic field of . If the value of is , what will be the frequency of revolution of the electron?

1.		2.
3.		4.

A metallic rod of mass per unit length of kgm^–1 is lying horizontally on a smooth inclined plane which makes an angle of with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction of T is acting on it in the vertical direction. What is the current flowing through the rod to keep it stationary?

1.	A	2.	A
3.	A	4.	A

Ionized hydrogen atoms and particles with the same momenta enter perpendicular to a constant magnetic field, . The ratio of their path radii will be:

1.		2.
3.		4.

An infinitely long straight conductor carries a current of as shown. An electron is moving with a speed of ${\mathrm{}}^{}$ parallel to the conductor. The perpendicular distance between the electron and the conductor is at an instant. Calculate the magnitude of the force experienced by the electron at that instant.

1.
2.
3.
4.

In the product
For and and what will be the complete expression for ?
1.
2.
3.
4.

A wire carrying a current along the positive -axis has length . It is kept in a magnetic field . The magnitude of the magnetic force acting on the wire is:
1.
2.
3.
4.

An electron (mass and charge ) moving with speed ( =speed of light) is injected into a magnetic field of magnitude perpendicular to its direction of motion. We wish to apply an uniform electric field together with the magnetic field so that the electron does not deflect from its path. Then (speed of light )

1.	is parallel to and its magnitude is
2.	is parallel to and its magnitude is
3.	is perpendicular to and its magnitude is
4.	is perpendicular to and its magnitude is