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DP IB Physics: SL

Topic Questions

Home / IB / Physics: SL / 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

A proton of mass m and electric charge q enters a region of magnetic field at point P and exits at point Q. The speed of the proton at P is v. The path followed by the proton is a quarter of a circle.

q1_magnetic-effects-of-electric-currents_ib-sl-physics-sq-medium  

(a)
State and explain whether the speed of the proton at P is the same as the speed at Q.
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    Question 1b

    Marks: 2
    (b)
    Outline why the path of the proton is circular.  
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      Question 1c

      Marks: 2
      (c)
      Show that the radius of the circular path is given by Rfraction numerator m v over denominator q B end fraction, where B is the magnetic flux density.
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        Question 1d

        Marks: 2

        The speed of the proton is 3.2 × 106 ms–1 at P and the magnetic flux density is 0.21 T.

        (d)
        Show that the radius of the path is 16 cm.
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          Question 2a

          Marks: 2

          The diagram shows a charged particle entering a region of magnetic field that is directed into the page.

          q2_magnetic-effects-of-electric-currents_ib-sl-physics-sq-medium

          The path of the particle is a quarter circle. 

          (a)
          Justify why the particle is positive.
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            Question 2b

            Marks: 3

            The proton enters the region with a speed of 5.4 × 106 ms–1. The magnetic flux density of the field is 0.35 T. 

            (b)
            Calculate the radius of the protons circular path.
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              Question 2c

              Marks: 3
              (c)
              Calculate the time the proton spends in the region of the magnetic field.
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                Question 2d

                Marks: 3

                The diagram shows the path of a charged particle passing through a thin metallic foil.

                q2d_magnetic-effects-of-electric-currents_ib-sl-physics-sq-medium 

                (d)
                State and explain the direction of motion of the particle and the sign of its charge.
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                  Question 3a

                  Marks: 5

                  Positive charges are seen passing through different magnetic fields. 

                  (a)
                  Determine the direction of the missing quantity between B, v and F for each:

                  q3a_magnetic-effects-of-electric-currents_ib-sl-physics-sq-medium
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                    Question 3b

                    Marks: 3

                    The diagram shows two parallel plates. The electric field between them is directed from top to bottom and has a magnitude 2.6 × 103 N C–1. The shaded region is a region of magnetic field normal to the page.q3b_magnetic-effects-of-electric-currents_ib-sl-physics-sq-medium

                    (b)
                    Deduce the magnetic field magnitude and direction so that an electron experiences zero net force when travelling through the plates with a speed of 3.0 × 105 ms–1.
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                      Question 3c

                      Marks: 2
                      (c)
                      Suggest and give a reason whether a proton shot with the same speed through the plates experiences zero net force.
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                        Question 3d

                        Marks: 3

                        The electron’s speed is halved. 

                        (d)
                        Suggest whether the electron would still be undeflected for the same magnetic field found in (b).
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                          Question 4a

                          Marks: 3

                          In the national grid electricity is generated by current carrying wires within a magnetic field. 

                          There are two wires carrying equal currents into the page.

                          q4_magnetic-effects-of-electric-currents_ib-sl-physics-sq-medium 

                          (a)
                          Determine the direction of the magnetic field at point X.    
                                 

                                    Use a diagram to help you with your answer.

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                            Question 4b

                            Marks: 2

                            A bar magnet is placed in a uniform magnetic field as shown in the diagram.

                            q4b_magnetic-effects-of-electric-currents_ib-sl-physics-sq-medium 

                            (b)
                            Suggest whether there is a net force on the bar magnet, causing it to move to a different position. Explain your answer.
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                              Question 4c

                              Marks: 2
                              (c)
                              The bar magnet does move in a specific type of motion. Determine how it will move.
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                                Question 4d

                                Marks: 2

                                A taut electrical wire carries electricity between a generator and the step-up transformer. The current is 2000 A and the magnetic field of the Earth at the position of the wire is 4.50 × 10–5 T and makes an angle of 45⁰ below the horizontal. 

                                (d)
                                Calculate the force experienced by a 25.0 m length of this wire.
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                                  Question 5a

                                  Marks: 2

                                  A current I passes through a conductor. The electrons move with a drift speed v. A magnetic field B at right angles to the direction of motion of the electrons is also present in the conductor.  

                                  q5_magnetic-effects-of-electric-currents_ib-sl-physics-sq-medium

                                  (a)
                                  Draw the arrows to indicate the directions of the: 

                                  (i)   Conventional current in the conductor

                                  (ii)   Magnetic force on the electron

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                                    Key Concepts
                                    Right Hand Rule

                                    Question 5b

                                    Marks: 3

                                    A is the cross-sectional area of the conductor, q is the charge of one electron, n is the number of electrons per unit volume and v is the drift speed of the electrons. 

                                    (b)
                                    Show that the current on the conductor is given by I = qnAv.

                                     

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                                      Question 5c

                                      Marks: 2

                                      The number density of the electrons is 3.5 × 1028 m–3. The current in the wire is 0.30 A and its cross-sectional area is 4.4 × 10–6 m2

                                      (c)
                                      Hence, calculate the drift velocity of the electrons moving in the conductor.
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                                        Question 5d

                                        Marks: 2

                                        The magnitude of the magnetic field within this current carrying conductor is 0.30 T. 

                                        (d)
                                        Calculate the magnitude of the force on the electrons in the conductor.
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