Apply Fleming's Right-Hand Rule
Scenario
Bina battery ke ek cycle dynamo light jala deta hai. Wahan cycle ka pahiya magnet aur wire ko ghumata hai.
Lekin motion se current kis disha mein banega, yeh kaise pata lagayein?
Mental model
Right Hand FBI: Thumb (Motion), First finger (Field), Central finger (Current). Generator rule.
Jaise left hand motor (motion banane) ke liye tha, waise hi right hand generator (current banane) ke liye hai. Apna daahina haath lo, pehli teen ungliyon ko ek doosre ke 90 degree par phailao. Agar thumb push ya motion dikhata hai, aur pehli ungli magnetic field, toh beech wali ungli banne wale (induced) current ki disha batayegi.
Explanation
Jab hum ek conductor ko magnetic field ke andar move karte hain, toh usme electromagnetic induction ki wajah se ek current paida (induce) hota hai. Is induced current ki disha (direction) nikalne ke liye hum **Fleming's Right-Hand Rule** ka use karte hain.
Is rule ke hisaab se apne right hand ke thumb (anguthe), forefinger (pehli ungli), aur middle finger (beech ki ungli) ko is tarah stretch karo ki wo teeno ek doosre ke perpendicular (right angles) hon.
- **Forefinger** hamesha **Magnetic Field** ki direction mein point karegi (North se South).
- **Thumb** hamesha conductor ke **Motion** (push) ki direction ko point karega.
- Toh jo **Middle finger** hai, wo apne aap **Induced Current** ki direction dikhayegi.
Ise yaad rakhne ka tareeka wahi FBI (Force/Motion, Magnetic Field, Current) hai, lekin dhyaan rahe ki ye Right Hand hai. Right hand hamesha electricity *generate* (paida) karne ke liye hota hai (jaise electric generator), jabki Left hand motors ke liye hota hai jahan current pehle se hota hai aur force nikalna hota hai.
Worked example
Problem: A straight wire is moved upwards (+y) in a magnetic field that points from left to right (+x). In which direction will the induced current flow?
- Right hand ki pehli ungli ko field ki direction (+x, right) mein point karo.
- Ab thumb ko motion ki direction (+y, up) mein point karo.
- Is position mein middle finger aapki screen ke andar point karegi.
Answer: The induced current will flow into the page (-z direction).
Problem: If the magnetic field is pointing downwards and you push the wire towards the East, what will be the direction of the induced current?
- Forefinger ko downward point karo.
- Thumb ko East ki taraf point karo.
- Aapki middle finger naturally North ki taraf point karegi.
Answer: The induced current will flow towards the North.
Key points
- Thumb (Motion): Points in the direction of the motion (or force applied) on the conductor.
- Forefinger (Field): Points in the direction of the magnetic field (N to S).
- Middle Finger (Current): Indicates the direction of the induced current.
Common mistakes
- Using the left hand instead of the right: Exam mein bacche aksar induced current nikalne ke liye bhi apna left hand utha lete hain aur galat answer likh aate hain. Generator (induced current) ke liye hamesha Right hand use hota hai.
Recall questions
- Which rule is used to find the direction of induced current?
- In Fleming's Right-Hand Rule, what does the middle finger represent?
- What do the thumb and forefinger represent in Fleming's Right-Hand Rule?
Questions & answers
State Fleming's right-hand rule.
Stretch the thumb, forefinger and middle finger of right hand so that they are mutually perpendicular. If the forefinger indicates the direction of the magnetic field and the thumb shows the direction of motion of conductor, then the middle finger will show the direction of induced current.
Approach: Describe the hand position and state what each of the three fingers represents.
A metal rod is moved towards the right in a uniform magnetic field that points into the page. What is the direction of the induced current?
Upwards.
Approach: Point forefinger into the page, thumb to the right. The middle finger points upwards.
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