A flux density of 1.2Wb/m^2 is required in the 1 mm air gap of an electromagnet having an iron path of length 1.5 m. Calculate the mmf required. Given, relative permeability of iron is 1600. Neglect leakage.

The mmf required is × A

Explanation:

The Magnetomotive force (mmf) is given by the formula below

where is the Magnetomotive force (mmf)

is the Magnetic field strength

is the magnetic length

The magnetic permeability μ is given by

μ =

Where is the Magnetic flux density

and is the Magnetic field strength

From the question,

= 1.2Wb/m^2

μ = 1600m

From μ =

∴μ

× A/m

Now, for the Magnetomotive force (mmf)

From the question

= 1.5 m

∴ × ×

×

Hence, The mmf required is × A

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27