electromagnetism and the motor effect

• What is produced around a conducting wire when current flows through it?

  A magnetic field
• What is a conducting wire?

  A wire with current flowing through it
• How can the shape and direction of the magnetic field around a wire be investigated?

  Using plotting compasses
• What does the magnetic field around a current-carrying wire look like?

  • Made up of concentric circles
  • Indicates no poles
  • Circles get further apart with distance
• What does the distance from the wire indicate about the magnetic field strength?

  It gets weaker as distance increases
• What rule is used to determine the direction of the magnetic field around a wire?

  The right-hand thumb rule
• What happens to the magnetic field direction if the current direction is reversed?

  The direction of the magnetic field reverses
• What occurs if there is no current flowing through the conductor?

  No magnetic field is produced
• How does increasing the current affect the magnetic field strength?

  It increases the strength of the magnetic field
• What factors affect the strength of the magnetic field around a wire?

  • Size of the current
  • Distance from the conductor
• What happens to the field lines as the current increases?

  They become closer together
• What is the magnetic field pattern around a solenoid?

  • Field lines circle around each part
  • Similar to that of a bar magnet
• How can the strength of the magnetic field around a wire be increased?

  By coiling the wire into a solenoid
• What is the magnetic field like inside a solenoid?

  • Strong and uniform
  • Fields from coils add together
• What happens to the magnetic field outside the solenoid?

  It becomes weaker
• How can the polarity of a solenoid be determined?

  By viewing it from the end
• What indicates a south pole in a solenoid?

  Current flowing clockwise
• What indicates a north pole in a solenoid?

  Current flowing anticlockwise
• What happens to the poles if the current direction changes?

  The north and south poles reverse
• What happens if there is no current flowing through the solenoid?

  No magnetic field is produced
• How can the strength of the magnetic field around a solenoid be increased?

  • Increase the current size
  • Increase the number of coils
  • Add an iron core
• What does an iron core do when current flows through the coils?

  It becomes an induced magnet
• What does 'uniform field' mean?

  • Same strength and direction at all points
  • Represented by parallel field lines
• What occurs when a wire with current is placed in a magnetic field?

  It experiences a force
• What causes the motor effect?

  Interactions between two magnetic fields
• How can the size of the force on a current-carrying conductor be increased?

  By increasing the current or using stronger magnets
• What happens when the wire is placed at 90 degrees to the magnetic field lines?

  It results in maximum interaction
• What is Fleming's left-hand rule used for?

  To determine directions of force, field, and current
• What are the steps to use Fleming's left-hand rule?

  1. Point first finger in direction of magnetic field
  2. Rotate hand so second finger points in direction of current
  3. Thumb points in direction of thrust (force)
• What is the equation to calculate the force on a current-carrying wire?

  F = BIL
• What do the variables in the equation F = BIL represent?

  F = force, B = magnetic flux density, I = current, L = length
• If a 5 cm length of wire carries 1.5 A and experiences a force of 0.06 N, how do you calculate the magnetic flux density?

  Use F = BIL
• What is the expectation regarding calculating force on a wire?

  Only when the wire is perpendicular to the field