Magnetic Effects of Electric Current : āĻŦā§āĻĻā§āĻ¯ā§āĻ¤āĻŋāĻ āĻ§āĻžā§°āĻžā§° āĻā§āĻŽā§āĻŦāĻā§āĻ¯āĻŧ āĻĒā§ā§°āĻāĻžā§ą : PYQ 1
5 Marks PYQ : ā§Ģ āĻ¨āĻŽā§āĻŦā§° āĻā§ā§°ā§āĻ¤ā§āĻŦāĻĒā§ā§°ā§āĻŖ āĻĒā§ā§°āĻļā§āĻ¨
Q8. Describe the construction and working of a DC electric motor with a neat labelled diagram.
āĻĒā§ā§°āĻļā§āĻ¨: āĻāĻāĻž DC āĻŦā§āĻĻā§āĻ¯ā§āĻ¤āĻŋāĻ āĻŽā§āĻā§°ā§° āĻāĻ āĻ¨ āĻā§°ā§ āĻāĻžā§°ā§āĻ¯āĻĒā§ā§°āĻŖāĻžāĻ˛ā§ āĻāĻāĻž āĻ¸ā§āĻļā§āĻā§āĻāĻ˛ āĻ˛ā§āĻŦā§āĻ˛āĻ¯ā§āĻā§āĻ¤ āĻāĻŋāĻ¤ā§ā§°āĻ¸āĻš āĻŦā§°ā§āĻŖāĻ¨āĻž āĻā§°āĻžāĨ¤
Ans:
Construction (āĻāĻ āĻ¨):
- Rectangular Coil (Armature): A coil of insulated copper wire wound on a soft iron core. āĻāĻ¯āĻŧāĻ¤āĻžāĻāĻžā§° āĻāĻ¯āĻŧā§āĻ˛ (āĻā§°ā§āĻŽā§āĻāĻžā§°): āĻāĻ¨āĻā§āĻ˛ā§āĻā§āĻĄ āĻ¤āĻžāĻŽā§° āĻ¤āĻžāĻā§°āĻ¤ āĻ¤ā§āĻ¯āĻŧāĻžā§° āĻāĻ¯āĻŧā§āĻ˛, āĻ¨ā§°āĻŽ āĻ˛ā§āĻšāĻžā§° āĻā§ā§°āĻ¤ āĻĒā§āĻāĻā§ā§ąāĻž āĻĨāĻžāĻā§āĨ¤
- Strong Magnetic Field: Provided by permanent magnets. āĻļāĻā§āĻ¤āĻŋāĻļāĻžāĻ˛ā§ āĻā§āĻŽā§āĻŦāĻā§āĻ¯āĻŧ āĻā§āĻˇā§āĻ¤ā§ā§°: āĻ¸ā§āĻĨāĻžāĻ¯āĻŧā§ āĻā§āĻŽā§āĻŦāĻā§ āĻĒā§ā§°āĻĻāĻžāĻ¨ āĻā§°ā§āĨ¤
- Split Ring Commutator: Reverses the direction of current after every half rotation. āĻ¸ā§āĻĒā§āĻ˛āĻŋāĻ ā§°āĻŋāĻ āĻāĻŽāĻŋāĻāĻā§āĻā§°: āĻĒā§ā§°āĻ¤āĻŋ āĻ ā§°ā§āĻ§-āĻā§ā§°ā§āĻŖāĻ¨ā§° āĻĒāĻŋāĻāĻ¤ āĻ§āĻžā§°āĻžā§° āĻĻāĻŋāĻļ āĻ¸āĻ˛āĻ¨āĻŋ āĻā§°ā§āĨ¤
- Carbon Brushes: Help in supplying current to the coil. āĻāĻžā§°ā§āĻŦāĻ¨ āĻŦā§ā§°āĻžāĻļ: āĻāĻ¯āĻŧā§āĻ˛āĻ˛ā§ āĻ§āĻžā§°āĻž āĻ¯ā§āĻāĻžāĻ¨ āĻ§ā§°ā§āĨ¤
- DC Power Supply: Provides electrical energy. DC āĻŦāĻŋāĻĻā§āĻ¯ā§ā§ āĻ¯ā§āĻāĻžāĻ¨: āĻŦā§āĻĻā§āĻ¯ā§āĻ¤āĻŋāĻ āĻļāĻā§āĻ¤āĻŋ āĻĒā§ā§°āĻĻāĻžāĻ¨ āĻā§°ā§āĨ¤
Working (āĻāĻžā§°ā§āĻ¯āĻĒā§ā§°āĻŖāĻžāĻ˛ā§): When electric current flows through the coil placed inside a magnetic field, the two sides of the coil experience forces in opposite directions (according to Fleming’s Left Hand Rule). This produces rotation of the coil.
The split ring reverses the current direction after each half turn, allowing the coil to continue rotating in the same direction.
āĻā§āĻŽā§āĻŦāĻā§āĻ¯āĻŧ āĻā§āĻˇā§āĻ¤ā§ā§°ā§° āĻŽāĻžāĻāĻ¤ āĻāĻ¯āĻŧā§āĻ˛ā§° āĻŽāĻžāĻā§ā§°ā§ āĻ§āĻžā§°āĻž āĻŦā§ā§ąāĻžāĻ˛ā§ āĻāĻ¯āĻŧā§āĻ˛ā§° āĻĻā§āĻ¯āĻŧā§āĻĢāĻžāĻ˛ā§ āĻŦāĻŋāĻĒā§°ā§āĻ¤ āĻŦāĻ˛ āĻ˛āĻžāĻā§ (āĻĢā§āĻ˛ā§āĻŽāĻŋāĻā§° āĻŦāĻžāĻāĻ āĻšāĻžāĻ¤ā§° āĻ¨āĻŋāĻ¯āĻŧāĻŽ āĻ āĻ¨ā§āĻ¸āĻžā§°ā§)āĨ¤ āĻĢāĻ˛āĻ¤ āĻāĻ¯āĻŧā§āĻ˛āĻā§ āĻā§ā§°ā§āĨ¤
āĻ¸ā§āĻĒā§āĻ˛āĻŋāĻ ā§°āĻŋāĻ āĻ§āĻžā§°āĻžā§° āĻĻāĻŋāĻļ āĻ¸āĻ˛āĻ¨āĻŋ āĻā§°āĻŋ āĻāĻ¯āĻŧā§āĻ˛āĻā§ āĻāĻā§ āĻĻāĻŋāĻļāĻ¤ā§ āĻ āĻŦāĻŋā§°āĻ¤ āĻā§ā§°āĻŋāĻŦāĻ˛ā§ āĻ¸āĻšāĻžāĻ¯āĻŧ āĻā§°ā§āĨ¤
Diagram Description (āĻāĻŋāĻ¤ā§ā§° āĻŦā§°ā§āĻŖāĻ¨āĻž): Label the following parts in the diagram:
- Battery / DC Supply → āĻŦā§āĻ¯āĻžāĻāĻžā§°ā§
- Split Ring → āĻ¸ā§āĻĒā§āĻ˛āĻŋāĻ ā§°āĻŋāĻ
- Carbon Brushes → āĻāĻžā§°ā§āĻŦāĻ¨ āĻŦā§ā§°āĻžāĻļ
- Armature → āĻā§°ā§āĻŽā§āĻāĻžā§°
- North & South Poles → āĻāĻ¤ā§āĻ¤ā§° āĻā§°ā§ āĻĻāĻā§āĻˇāĻŋāĻŖ āĻŽā§āĻ°ā§
- Direction of Rotation → āĻā§ā§°ā§āĻŖāĻ¨ā§° āĻĻāĻŋāĻļ
(Tip: Always draw a neat diagram in exams for full marks.) āĻĒā§°ā§āĻā§āĻˇāĻžāĻ¤ āĻ¸āĻŽā§āĻĒā§ā§°ā§āĻŖ āĻ¨āĻŽā§āĻŦā§° āĻĒāĻžāĻŦāĻ˛ā§ āĻ¸āĻĻāĻžāĻ¯āĻŧ āĻāĻāĻž āĻĒā§°āĻŋāĻˇā§āĻāĻžā§° āĻāĻŋāĻ¤ā§ā§° āĻāĻāĻāĻŋāĻŦāĻžāĨ¤
Q9. State and explain Fleming's Right Hand Rule. Where is it used ? āĻĒā§ā§°āĻļā§āĻ¨: āĻĢā§āĻ˛ā§āĻŽāĻŋāĻā§° āĻ¸ā§āĻ āĻšāĻžāĻ¤ā§° āĻ¨āĻŋāĻ¯āĻŧāĻŽ āĻāĻ˛ā§āĻ˛ā§āĻ āĻā§°ā§ āĻŦā§āĻ¯āĻžāĻā§āĻ¯āĻž āĻā§°āĻžāĨ¤ āĻāĻ¯āĻŧāĻžāĻ āĻ’āĻ¤ āĻŦā§āĻ¯ā§ąāĻšāĻžā§° āĻā§°āĻž āĻšāĻ¯āĻŧ ?
Ans: Stretch the thumb, forefinger, and middle finger of the right hand so that they are mutually perpendicular.
- Thumb → Direction of motion of conductor
- Forefinger → Direction of magnetic field
- Middle finger → Direction of induced current
āĻ¸ā§āĻ āĻšāĻžāĻ¤ā§° āĻŦā§āĻĸāĻŧāĻž āĻāĻā§āĻ˛āĻŋ, āĻ¤ā§°ā§āĻāĻ¨ā§ āĻā§°ā§ āĻŽāĻžāĻā§° āĻāĻā§āĻ˛āĻŋāĻā§ āĻĒā§°āĻ¸ā§āĻĒā§°ā§° āĻĒā§ā§°āĻ¤āĻŋ āĻ˛āĻŽā§āĻŦāĻāĻžāĻŦā§ āĻŽā§āĻ˛āĻŋ āĻ§ā§°āĻŋāĻŦāĻžāĨ¤
- āĻŦā§āĻĸāĻŧāĻž āĻāĻā§āĻ˛āĻŋ → āĻĒā§°āĻŋāĻŦāĻžāĻšāĻā§° āĻāĻ¤āĻŋā§° āĻĻāĻŋāĻļ
- āĻ¤ā§°ā§āĻāĻ¨ā§ → āĻā§āĻŽā§āĻŦāĻā§āĻ¯āĻŧ āĻā§āĻˇā§āĻ¤ā§ā§°ā§° āĻĻāĻŋāĻļ
- āĻŽāĻžāĻā§° āĻāĻā§āĻ˛āĻŋ → āĻāĻĻā§āĻĻā§āĻĒāĻŋāĻ¤ āĻ§āĻžā§°āĻžā§° āĻĻāĻŋāĻļ
Use (āĻŦā§āĻ¯ā§ąāĻšāĻžā§°): Used in electric generators to determine the direction of induced current. āĻāĻ˛ā§āĻā§āĻā§ā§°āĻŋāĻ āĻā§āĻ¨ā§ā§°ā§āĻā§°āĻ¤ āĻāĻĻā§āĻĻā§āĻĒāĻŋāĻ¤ āĻ§āĻžā§°āĻžā§° āĻĻāĻŋāĻļ āĻ¨āĻŋā§°ā§āĻŖāĻ¯āĻŧ āĻā§°āĻŋāĻŦāĻ˛ā§ āĻŦā§āĻ¯ā§ąāĻšāĻžā§° āĻā§°āĻž āĻšāĻ¯āĻŧāĨ¤
Numerical PYQ (3 Marks) : āĻ¸āĻāĻā§āĻ¯āĻžāĻāĻ¤ āĻĒā§ā§°āĻļā§āĻ¨
Q10. A current of 5 A flows through a conductor for 2 minutes. Find the charge.
Given (āĻĻāĻŋāĻ¯āĻŧāĻž āĻāĻā§):
Current (I) = 5 A
Time (t) = 2 minutes = 120 seconds
Formula: Q = I × t
Soln:
Q = 5 × 120
Q = 600 Coulomb (C)
Ans: 600 C
Most Repeated PYQ Topics (Exam Tip) : āĻŦā§āĻāĻŋāĻā§ āĻ¸ā§āĻ§āĻž āĻĒā§ā§°āĻļā§āĻ¨āĻ¸āĻŽā§āĻš
Fleming’s Left & Right Hand Rules : āĻĢā§āĻ˛ā§āĻŽāĻŋāĻā§° āĻŦāĻžāĻāĻ āĻā§°ā§ āĻ¸ā§āĻ āĻšāĻžāĻ¤ā§° āĻ¨āĻŋāĻ¯āĻŧāĻŽ
- Electric Motor & Generator : āĻŦā§āĻĻā§āĻ¯ā§āĻ¤āĻŋāĻ āĻŽā§āĻā§° āĻā§°ā§ āĻā§āĻ¨ā§ā§°ā§āĻā§°
- Electromagnet vs Permanent Magnet : āĻāĻ˛ā§āĻā§āĻā§ā§°ā§āĻŽā§āĻāĻ¨ā§āĻ āĻŦāĻ¨āĻžāĻŽ āĻ¸ā§āĻĨāĻžāĻ¯āĻŧā§ āĻā§āĻŽā§āĻŦāĻ
- Direction of Magnetic Field : āĻā§āĻŽā§āĻŦāĻā§āĻ¯āĻŧ āĻā§āĻˇā§āĻ¤ā§ā§°ā§° āĻĻāĻŋāĻļ
- Numericals based on Q = I × t : Q = I × t āĻāĻŋāĻ¤ā§āĻ¤āĻŋāĻ āĻ¸āĻāĻā§āĻ¯āĻžāĻāĻ¤ āĻĒā§ā§°āĻļā§āĻ¨