Full Answer Section

where:

• F is the force in Newtons
• N is the number of turns of the coil
• I is the current in Amperes
• μ₀ is the permeability of free space (4π × 10^-7 T·m/A)
• A is the cross-sectional area of the core
• g is the air gap distance

Calculating the Effective Magnetomotive Force (MMF):

Given that 15% of the total MMF is expended on the iron part, 85% is available for the air gap.

MMF_air_gap = 0.85 * N * I

Relating MMF to Magnetic Field Intensity (H):

For the air gap:

H = MMF_air_gap / (2 * g)

Relating Magnetic Field Intensity to Magnetic Flux Density (B):

B = μ₀ * H

Relating Magnetic Flux Density to Force:

The force on the armature is given by:

F = (B^2 * A) / (2 * μ₀)

Combining Equations and Solving for I:

By substituting the expressions for B and H into the force equation and rearranging, we can solve for the current I.

Note: To simplify the calculations, we can combine the equations and directly solve for I in terms of the given parameters.

After calculating the required current, it’s essential to consider the practical limitations of the electromagnet, such as the maximum current capacity of the wire and the power supply.