Reading Time: 2 minutesTorque (
Electric Motors: Exploring Torque, Magnetic Fields, and Energy Conversion
What Are Electric Motors?
Electric motors convert electrical energy into mechanical energy using the interaction between magnetic fields and current-carrying conductors.
Key Concepts in Electric Motors
Magnetic Force on a Current-Carrying Wire
The force on a wire in a magnetic field is given by:
![\[ F = BIL \sin\theta \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-356e0092f4ef997893cd292013ef0ea6_l3.png "Rendered by QuickLaTeX.com")
Where:
: Magnetic field strength (T, Tesla)
: Current (A, Amperes)
: Length of wire in the field (m)- : Angle between and
: Magnetic field strength (T, Tesla)
: Current (A, Amperes)
: Length of wire in the field (m)
: Angle between Torque (
) in Motors
) in MotorsThe rotational force in a motor coil:
![\[ \tau = BIA N \sin\theta \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-2161f9bfa3a7012cf50740d2921b6682_l3.png "Rendered by QuickLaTeX.com")
Where:
: Area of the loop (m²)
: Number of turns in the coil- : Angle between field and coil normal
: Area of the loop (m²)
: Number of turns in the coilApplications of Electric Motors
Transportation
- Electric vehicles (torque: 200-500 N·m typical)
- High-speed trains (power: 5-10 MW per motor)
Industry
- Conveyor systems (1-50 HP motors)
- Robotic arms (precision servo motors)
Home Appliances
- Washing machines (universal motors)
- Refrigerator compressors (induction motors)
Example Problem
A rectangular loop (
) has 100 turns, carries 
, and is in a 
field. Find maximum torque.
- Calculate Area:
- Maximum Torque (
):
![\[ A = 0.1 \, \text{m} \times 0.05 \, \text{m} = 0.005 \, \text{m}^2 \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-c0de47074d60d515afda53d686761da3_l3.png "Rendered by QuickLaTeX.com")
): ![\[ \tau = (0.5)(3)(0.005)(100)\sin 90^\circ = 0.75 \, \text{N·m} \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-3393f82c1698c063777305e994d3c513_l3.png "Rendered by QuickLaTeX.com")
Common Mistakes
- Using cm instead of m for area calculations
- Omitting the
term in torque calculations - Confusing motor torque (
) with linear force (
)
term in torque calculations
) with linear force (
)Practice Questions
- Calculate torque for a circular loop (,
) with 
current in 
field. - Explain how commutators maintain rotation in DC motors.
- Compare induction vs. synchronous motor applications.
, 
) with 
current in 
field.