The rule to determine the direction of a current induced in a coil due to its rotation in a magnetic field is:
- A.Right-Hand Thumb Rule.
- B.Fleming's Left-Hand Rule.
- C.Fleming's Right-Hand Rule.
- D.Hund's Rule.
Correct answer
Explanation
The correct answer is C, Fleming's Right-Hand Rule. When a conductor moves in a magnetic field and a current is induced in it, this rule gives the direction of that induced current.
Stretch the thumb, forefinger and middle finger of the right hand at right angles to one another. If the forefinger points along the magnetic field and the thumb along the motion of the conductor, the middle finger shows the direction of the induced current. This is the principle of the electric generator, or dynamo, in which a coil rotating in a magnetic field produces electricity by electromagnetic induction, discovered by Michael Faraday in 1831. The rule is also called the generator rule.
A is wrong: the right-hand thumb rule gives the direction of the magnetic field around a current-carrying wire.
B is wrong: Fleming's left-hand rule gives the direction of the force on a current-carrying conductor in a field, the principle of the electric motor.
D is wrong: Hund's rule is a chemistry rule about how electrons fill orbitals of equal energy.
Exam tip: right hand = generator (induced current); left hand = motor (force); thumb rule = field around a wire.
Practice Questions
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