Question

Which of the following is used to determine the direction of induced current in a generator?

• A. Fleming's left hand rule
• B. Right hand thumb rule
• C. Left hand thumb rule
• D. Fleming's right hand rule

Answer 1

The correct option is D

Fleming's right hand rule

Explanation of correct option

Option D,

Fleming's right-hand rule

1. According to Fleming's right-hand rule, when the thumb, forefinger, and middle finger of the right hand are perpendicular to each other, then if the thumb denotes the direction of motion of the conductor, the forefinger denotes the direction of the magnetic field, then the middle finger will represent the direction of induced current.
   
2. Fleming's right-hand rule is mainly applicable to generators.
3. So, here Fleming's right-hand rule is used in the case of a generator to determine the direction of the induced current.

Explanation of incorrect option

Option A,

Fleming's left-hand rule

1. When a current-carrying conductor is placed in an external magnetic field, the conductor experiences a force perpendicular to both the field and to the direction of the current flow.
2. So, it is used in the case of motor to find the direction of the force in the current carrying coil placed in magnetic field.

Option B,

Right hand thumb rule,

1. If a current carrying conductor is imagined to be held in your right hand such that the thumb points along the direction of the current, then the direction of the wrapped fingers will give the direction of magnetic field lines.
   
2. In the figure, I indicates the current and B indicates the magnetic field.

Option C,

Left hand thumb rule

1. There is no rule called the left-hand thumb rule.

Therefore, Option D is correct.