Calculate Physical Properties of Coil


The coil is the most recognizable form of an inductor. Both inductors and electromagnets consist of wires wound around a bobbin or core form and the coiled wire is known as the winding. The center of the coil is referred as the core.

Each individual loop of wire is called a turn. To prevent short-circuit because of the turns the wire needs insulation, such as plastic or enamel coating. Finally to secure the winding, it is often wrapped around a coil form made of materials like plastic. In designing and constructing the coil like this, it becomes necessary to estimate the cross sectional area, and resistance of the coil.

This online electrical calculator helps you calculate the physical characteristics of a coil or material, including resistance, total wire length, and number of windings. The calculator assumes the wire to be copper when calculating resistance and voltage.

Understanding Physical properties of Coil:

Here’s a comprehensive overview of the key physical properties of coils:

Stiffness: “The stiffness of coils is an essential characteristic, influenced by various factors. It increases with the fourth power of diameter D1, is directly associated with the G value of the wire used, and decreases with the cube of the mean diameter D2 of the coil. Therefore, coils with larger diameters, denser wire, and fewer wraps per unit length exhibit greater stiffness.”

Diameter: The size of the coil (D1) plays a pivotal role in determining its stiffness; larger diameters contribute to increased stiffness. Additionally, the coil’s diameter influences its capacity to endure external pressures like compression and tension.

Wire density: The coil’s rigidity is notably influenced by the density of the wire (G) employed in its construction, where wires of greater density lead to coils with increased stiffness.

Mean diameter: The average coil diameter (D2) demonstrates an inverse relationship with stiffness, indicating that coils featuring smaller average diameters exhibit lower stiffness levels.

Number of wraps: The quantity of coils wound per unit length (referred to as n) around the shaping mandrel during the creation of the secondary layout, commonly termed as the primary winding of the coil, exhibits an inverse correlation with stiffness. A reduced number of wraps corresponds to a higher stiffness in the coil.

Composition: The configuration of the coil, comprising its material type and quantity, can impact its physical characteristics. For instance, coils crafted from specific alloys might exhibit enhanced resistance to corrosion or increased strength.

Detachment mechanism: The way the coil is disconnected, including factors like the detachment mechanism type or the materials employed, can influence its physical characteristics and operational effectiveness.

Size: The dimensions of a coil play a pivotal role in shaping its physical characteristics, as larger coils often exhibit distinct properties compared to their smaller counterparts.

Shape: The physical characteristics and efficiency of the coil can be influenced by its configuration, encompassing aspects such as the curvature and orientation of the wire used.

Material properties: The characteristics of the material utilized in forming the coil, including its Young’s modulus, Poisson’s ratio, and density, can influence its physical attributes and performance.


Electrical transformers.

Magnetic resonance imaging (MRI) machines.





In summary, the performance and appropriateness of coils for diverse applications, including medical equipment, electrical parts, and mechanical mechanisms, heavily rely on their inherent physical characteristics.

Wire Diameter (d)
Number Of Turns
Bobbin Length (bl)
Bobbin Diameter (bd)
Current (I)


\[T= \frac {bl}{d}\]
\[n= \frac {Turns}{T}\]
\[cd = (2 * n * d) + bd \]
\[r= \frac {n * d + bd}{2}\]
\[a = pi * r * r\]
\[L= \frac {2 * pi * r * n}{1000}\]
\[rpm = 0.0333 * \frac {\left( \frac {0.812}{2}\right)^2}{\left(\frac{d}{2}\right)^2}\]
\[R= rpm * L\]
\[V = R * I\]
\[P= V* I\]

where :

  • T = Turns per winding,
  • bl = Length of Bobbin,
  • d = Wire Diameter,
  • n = Number of windings,
  • cd = Outer diameter of the coil,
  • bd = Diameter of Bobbin,
  • r = radius of the middle of the coil,
  • a = Cross-sectional area,
  • L = Total Length,
  • rpm = Resistance/meter,
  • R = Resistance,
  • V = Voltage at Rated Current,
  • I = Current,
  • P = Power at Rated Current,

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