PHY_10_57_V2_DM_Magnetic properties of a substance

Worksheet

1.      Charged particles, each of mass m and charge Q, travel at a constant speed in a circle of radius r in a uniform magnetic field of flux density B.

Which expression gives the frequency of rotation of a particle in the beam?

2.      The path followed by an electron of momentum p, carrying charge –e, which enters a magnetic field at right angles, is a circular arc of radius r.

What would be the radius of the circular arc followed by an α particle of momentum 2p, carrying charge +2e, which entered the same field at right angles?

A       

B        r

C        2r

D        4r

3.      Which one of the following statements is correct?

An electron follows a circular path when it is moving at right angles to

A       a uniform magnetic field.

B       a uniform electric field.

C       uniform electric and magnetic fields which are perpendicular.

D       uniform electric and magnetic fields which are in opposite directions.

4.      Two electrons, X and Y, travel at right angles to a uniform magnetic field.

X experiences a magnetic force, F_X, and Y experiences a magnetic force, F_Y.

What is the ratio  if the kinetic energy of X is half that of Y?

A       

B       

C      

D       1

5.      A negatively charged particle moves at right angles to a uniform magnetic field. The magnetic force on the particle acts

A       in the direction of the field.

B       in the opposite direction to that of the field.

C       at an angle between 0° and 90° to the field.

D       at right angles to the field.

6.      Two charged particles, P and Q, move in circular orbits in a magnetic field of uniform flux density. The particles have the same charge but the mass of P is less than the mass of Q. T_P is the time taken for particle P to complete one orbit and T_Q the time for particle Q to complete one orbit. Which one of the following is correct?

A       T_P = T_Q

B       T_P> T_Q

C       T_P< T_Q

D       T_P – T_Q= 1

7.      Charged particles, each of mass m and charge Q, travel at a constant speed in a circle of radius r in a uniform magnetic field of flux density B. Which expression gives the frequency of rotation of a particle in the beam?

A       

B       

C       

D       

8.      When a β particle moves at right angles through a uniform magnetic field it experiences a force F. An α particle moves at right angles through a magnetic field of twice the magnetic flux density with velocity one tenth the velocity of the β particle. What is the magnitude of the force on the α particle?

A       0.2 F

B       0.4 F

C       0.8 F

D       4.0 F

9.      A jet of air carrying positively charged particles is directed horizontally between the poles of a strong magnet, as shown in the diagram.

In which direction are the charged particles deflected?

A       upwards

B       downwards

C       towards the N pole of the magnet

D       towards the S pole of the magnet

10.  An electron moving with a constant speed enters a uniform magnetic field in a direction perpendicular to the magnetic field. What is the shape of the path that the electron would follow?

A       parabolic

B       circular

C       elliptical

D       a line parallel to the magnetic field

11.  An electron moving with a constant speed enters a uniform magnetic field in a direction at right angles to the field. What is the subsequent path of the electron?

A       A straight line in the direction of the field.

B       A straight line in a direction opposite to that of the field.

C       A circular arc in a plane perpendicular to the direction of the field.

D       An elliptical arc in a plane perpendicular to the direction of the field.

12.  The path followed by an electron of momentum p, carrying charge −e, which enters a magnetic field at right angles, is a circular arc of radius r.
What would be the radius of the circular arc followed by an α particle of momentum 2p, carrying charge +2e, which entered the same field at right angles?

A        

B       r

C       2r

D       4r

13.  Particles of mass m carrying a charge Q travel in a circular path of radius r in a magnetic field of flux density B with a speed v. How many of the following quantities, if changed one at a time, would change the radius of the path?

•    m

•    Q

•    B

•    v

A       one

B       two

C       three

D       four

14.  Protons, each of mass m and charge e, follow a circular path when travelling perpendicular to a magnetic field of uniform flux density B. What is the time taken for one complete orbit?

A      

B      

C      

D      

15.  Particles of mass m, each carrying charge Q and travelling with speed v, enter a magnetic field of flux density B at right angles. Which one of the following changes would produce an increase in the radius of the path of the particles?

A       an increase in Q

B       an increase in m

C       a decrease in v

D       an increase in B

16.  An electron moves due North in a horizontal plane with uniform speed. It enters a uniform magnetic field directed due South in the same plane. Which one of the following statements concerning the motion of the electron in the magnetic field is correct?

A       It continues to move North with its original speed.

B       It slows down to zero speed and then accelerates due South.

C       It is accelerated due West.

D       It is accelerated due North.

17.  An α particle and a β^– particle both enter the same uniform magnetic field, which is perpendicular to their direction of motion. If the β^– particle has a speed 15 times that of the α particle, what is the value of the ratio

?

A       3.7

B       7.5

C       60

D       112.5

18.  Which line, A to D, correctly describes the trajectory of charged particles which enter, at right angles, (a) a uniform electric field, and (b) a uniform magnetic field?

19.  An alpha particle moves at one-tenth the velocity of a beta particle. They both move through the same uniform magnetic field at right angles to their motion.

The magnitude of the ratio  is

A       

B       

C       

D       

20.  An electron moves into a region of uniform magnetic flux density between the poles of a magnet as shown in the diagram.

The deflection of the electron will be

A       towards the pole marked S

B       towards the pole marked N

C       perpendicular to the plane of the paper towards you

D       perpendicular to the plane of the paper away from you