0%

DP IB Physics: HL

Topic Questions

Home / IB / Physics: HL / DP / Topic Questions / 5. Electricity & Magnetism / 5.4 Magnetic Effects of Electric Currents / Structured Questions


5.4 Magnetic Effects of Electric Currents

Question 1a

Marks: 3

The diagram shows a current-carrying conductor at an angle θ to an external B field.

  1a-figure-1

   

The force acting on the current-carrying conductor when it lies at different angles to the field can be calculated using the equation

F space equals space B I L space sin space theta

 

(a)
State what the symbols B, I and L represent.

     

[3]

    Assess your score
      

    Question 1b

    Marks: 1
    (b)
    State the angle, θ, between the conductor and the B field which would result in the largest force being exerted on the conductor.

        

      [1]

      Assess your score
        

      Question 1c

      Marks: 1
      (c)
      State the angle, θ, between the conductor and the B field which would result in there being no force exerted on the conductor from the B field.
         

       [1]

        Assess your score
          

        Question 1d

        Marks: 3

        The conductor in the diagram in part (a) has a length of 1.2 m and a current of 0.85 A flowing through it. The conductor is placed at 30o to the B field, which has a magnetic flux density of 70 mT.

         

        (d)
        Calculate the force acting on the conductor.
           
        [3]
          Assess your score
            

          Question 2a

          Marks: 1

          The diagram shows a magnetic B field.

          q2b-figure-2

             

          (a)
          State whether the magnetic field is acting into or out of the page.
            
          [1]

            Assess your score
              
            Key Concepts
            Magnetic Fields

            Question 2b

            Marks: 2

            A circuit is built with a section of wire, between the points A and B, running perpendicular to a magnetic field.

            q2c-figure-3

            (b)
            When the switch is closed, state the direction of:

            (i)
            The current through wire AB. 
            [1]
            (ii)
            The force acting on wire AB.
            [1]
              Assess your score
                

              Question 2c

              Marks: 2
              (c)
              State two ways of increasing the size of the force acting on the current carrying conductor.
                 
              [2]
                Assess your score
                  

                Question 2d

                Marks: 3

                When the force, the magnetic field and the current are all mutually perpendicular to each other, the directions of each can be interpreted using a technique known as Fleming's Left Hand Rule.

                q2a-figure-1

                (d)
                State what is represented by the direction of:

                (i)
                The thumb
                [1]
                (ii)
                The first finger
                [1]
                (iii)
                The second finger
                [1]
                  Assess your score
                    
                  Key Concepts
                  Magnetic Fields

                  Question 3a

                  Marks: 2
                  (a)
                  Define magnetic flux density.
                     
                  [2]

                    Assess your score
                      
                    Key Concepts
                    Magnetic Fields

                    Question 3b

                    Marks: 1
                    (b)
                    State the unit for magnetic flux density.
                       

                    [1]

                      Assess your score
                        
                      Key Concepts
                      Magnetic Fields

                      Question 3c

                      Marks: 5

                      A wire of length 15 cm has a mass of 30 g and current of 2.0 A flowing through it. When the wire is placed inside a uniform magnetic field it 'floats' in equilibrium in the magnetic field.

                         

                      q3c-figure-1

                         

                      (c)

                      (i)
                      Calculate the weight of the wire
                      [3]
                           
                      (ii)
                      Hence determine the size of the force produced by the magnetic field acting on the wire when it is carrying current
                      [2]
                        Assess your score
                          

                        Question 3d

                        Marks: 3
                        (d)
                        Calculate the magnetic flux density required to keep the wire ‘floating’ in equilibrium.
                           
                        [3]
                          Assess your score
                            

                          Question 4a

                          Marks: 5

                          The equation used to calculate the force acting on a moving charged particle is

                          F space equals space q v B sin theta

                            

                          (a)
                          State what each symbol in the above equation represents.
                             
                          [5]
                            Assess your score
                              
                            Key Concepts
                            Magnetic Fields

                            Question 4b

                            Marks: 2

                            A beam of electrons is fired into a uniform magnetic field of flux density 0.5 T, as shown. An electron enters the magnetic field at point A.

                             q4b-figure-1

                               

                            (b)
                            Draw an arrow, labelled F, from point A to show the direction of the force acting on the electron.
                               
                            [2]

                             

                              Assess your score
                                

                              Question 4c

                              Marks: 2

                              The electron is travelling at a speed of 4.8 × 107 m s−1 in the magnetic field where magnetic flux density B = 0.5 T

                              (c)
                              Calculate the force on the electron when it enters the magnetic field and is travelling perpendicular to it.
                                
                              [2]

                                Assess your score
                                  

                                Question 4d

                                Marks: 4
                                (d)
                                On your sketch, continue the path of the electron beam

                                (i)
                                Through the magnetic field
                                [2]
                                (ii)
                                After it has emerged from the magnetic field
                                [2]
                                  Assess your score
                                    

                                  Question 5a

                                  Marks: 3

                                  When a moving charge enters a magnetic field the magnetic field produces a force on the charge, which can be calculated using

                                  F space equals space q v B sin theta

                                     

                                  where q = charge, v = velocity, B = magnetic flux density, and θ = the angle between the velocity of the charge and the direction of the magnetic field.

                                  The magnetic force provides the centripetal force which causes the charge to move in a circular orbit. The equation to calculate centripetal force acting on an object is

                                  F space equals fraction numerator m v squared over denominator r end fraction

                                   

                                  where m = mass of the object, v = speed of the object and r = radius of the circular orbit.

                                  (a)
                                  Using the equations given above, show that the radius of the circular orbit of the charged object inside the magnetic field can be given as  

                                  r space equals space fraction numerator m v over denominator q B end fraction
                                     
                                  [3]
                                    Assess your score
                                      

                                    Question 5b

                                    Marks: 3
                                    (b)
                                    State three ways of increasing the radius of the circular orbit.

                                     

                                    [3]

                                      Assess your score
                                        

                                      Question 5c

                                      Marks: 3

                                      An electron is travelling at right angles to a uniform magnetic field which has a magnetic flux density of 5.6 mT. The speed of the electron is 3.0 × 106 m s–1.

                                      (c)
                                      Use the following information to calculate the radius of the circular orbit of the electron:
                                      Mass of an electron, m = 9.11 × 10–31 kg
                                      Charge of an electron, q = 1.60 × 10–19 C

                                      [3]

                                        Assess your score
                                          

                                        Question 5d

                                        Marks: 1
                                        (d)
                                        Name the particle accelerator which accelerates charged particles along a spiral path.
                                          
                                        [1]
                                          Assess your score