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Magnetic fields and forcesEdexcel A-Level Physics: Flashcards

What these 13 flashcards ask

  • Define the tesla.
  • State the equation for the force on a current-carrying conductor in a magnetic field.
  • When is the force on a current-carrying wire zero?
  • State Fleming's left-hand rule.
  • State the equation for the force on a moving charge in a magnetic field.
  • Why does a magnetic field not change the speed of a moving charge?
  • What is the direction of the force on a moving charge relative to v and B?
  • How does the force on an electron differ from that on a proton moving the same way?
  • Define magnetic flux.
  • What is the weber in terms of tesla?
  • Define flux linkage.
  • How is flux calculated if the field makes an angle with the normal to the area?
  • In which orientation is the flux through a coil zero?

Exam questions on Magnetic fields and forces

  1. A 0.12 m length of straight copper wire carries a steady current of 5.0 A. It lies horizontally at right angles to a uniform horizontal magnetic field of flux density 0.30 T between the flat poles of a large magnet.
    The wire is turned, in the horizontal plane, so that it makes an angle of 30° with the field lines. The current is unchanged. Calculate the force on the wire.2 marks
  2. A proton enters a region of uniform magnetic field of flux density 0.050 T with a speed of 2.4 × 10⁶ m s⁻¹, moving at right angles to the field lines. The charge on a proton is 1.60 × 10⁻¹⁹ C and its mass is 1.67 × 10⁻²⁷ kg.
    Calculate the magnitude of the acceleration of the proton as it enters the field.2 marks
  3. A flat rectangular coil of 250 turns measures 8.0 cm by 5.0 cm. It is placed in a uniform magnetic field of flux density 0.18 T, with the plane of the coil initially perpendicular to the field lines.
    Calculate the magnetic flux through the coil and the flux linkage of the coil, and state the unit of flux linkage.3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).