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Electrical Engineering Objective Questions { Electromagnetism }

204. An air gap is usually inserted in magnetic circuits to
A. increase m.m.
B. increase the flux
C. prevent saturation
D. none of the above
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205. The relative permeability of a feromagnetic material is
A. less than one
B. more than one
C. more than 10
D. more than 100 or 1000
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206. The unit of magnetic flux is
A. henry
B. weber
C. amper re/metre
D. ampe e-turn/weber
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207. Permeability in a magnetic circuit corresponds to ...... in an electric circuit.
A. resistance
B. resistivity
C. conductivity
D. conductance
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208. Point out the wrong statement. magnetic leakage is undesirable in electric machines because it
A. lowers their power efficiency
B. increases their cost of manufacture
C. leads to their increased weight
D. produces fringing
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209. Relative permeability of vacuum is
B. I H/m
C. 1/4n
D. 4n x 10-7 H/m
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210. The magnetising force (H) and magnetic flux density are connected by the relation
A. B = prH/i.to
B. B = IAN
C.B = H/p.opl.
D. B = goH/pr
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