A-Level H2 物理筆記
Chapter 21: Electromagnetism
Magnetic effect of a current
Applications of the magnetic effect of a current
Force on a current-carrying conductor
(a) Draw the pattern of the magnetic field due to currents in straight wires and in solenoids and state the effect on the magnetic field of changing the magnitude and / or direction of the current.
(b) Describe the application of the magnetic effect of a current in a circuit breaker.
(c) Describe experiments to show the force on a current-carrying conductor, and on a beam of charged particles, in a magnetic field, including the effect of reversing:
(i) the current
(ii) the direction of the field
(d) Deduce the relative directions of force, field and current when any two of these quantities are at right angles to each other using Fleming’s left-hand rule.
(e) Describe the field patterns between currents in parallel conductors and relate these to the forces which exist between the conductors (excluding the Earth’s field).
(f) Explain how a current-carrying coil in a magnetic field experiences a turning effect and that the effect is increased by increasing:
(i) the number of turns on the coil
(ii) the current
(g) Discuss how this turning effect is used in the action of an electric motor.
(h) Describe the action of a split-ring commutator in a two-pole, single-coil motor and the effect of winding the coil on to a soft-iron cylinder.