NDA (I) 2022 General Ability Test · Question 96 of 150

Correct — C, induced current. Fleming's right-hand rule is the generator rule: with the thumb, forefinger and middle finger held mutually perpendicular, the forefinger points along the magnetic field, the thumb along the motion of the conductor, and the middle finger then gives the direction of the induced current. Because the conductor is moving through the field (electromagnetic induction), the middle finger predicts the direction of the induced current — not a force. Fleming's left-hand rule, by contrast, gives the force on a current-carrying conductor.

• (a)force acting on the conductor — That is what Fleming's left-hand rule gives — the motor rule, the force on a current-carrying conductor in a field. The right-hand rule is about induced current.
• (b)electric field — Fleming's rules deal with the magnetic field, the motion and the current, not the direction of an electric field.
• (d)current — The middle finger gives the direction of the induced current — the current produced by the conductor's motion through the field; plain 'current' omits that it is induced, so 'induced current' (c) is the precise answer.

Fleming's right-hand rule is used in electromagnetic induction (the generator/dynamo). When a conductor moves through a magnetic field, an EMF is induced and a current flows. Holding the first three fingers of the right hand at right angles, forefinger = field, thumb = motion, and middle finger = the direction of the induced current.

The key contrast is with Fleming's left-hand rule (the motor rule), which gives the force on a current-carrying conductor. Because here the conductor is moving and the current is a consequence, the right-hand rule predicts the induced current.

• Fleming's right-hand rule (generator) has forefinger = field, thumb = motion, and middle finger = induced current.
• It applies when a conductor moves through a magnetic field, inducing an EMF and current.
• Fleming's left-hand rule gives the force on a current-carrying conductor (motor rule).
• The three fingers are held mutually perpendicular (at right angles).

• Swapping the right-hand rule (induced current) with the left-hand rule (force).
• Choosing plain 'current' instead of the precise 'induced current'.

Tests which quantity Fleming's right-hand rule predicts — the direction of the induced current.

No directly related past PYQ was found.

• practice — not a real PYQ

  Fleming's left-hand rule is used to find the direction of the

  • (a)induced current
  • (b)force on a current-carrying conductor
  • (c)magnetic field
  • (d)EMF

  Answer(b) force on a current-carrying conductor — the motor rule.

• practice — not a real PYQ

  The direction of the current induced in a conductor moving through a magnetic field is given by

  • (a)Fleming's left-hand rule
  • (b)Fleming's right-hand rule
  • (c)Ohm's law
  • (d)Coulomb's law

  Answer(b) Fleming's right-hand rule.