Because of the skin depth effect, the current at high frequency tends to flow at very low depth from radius. Then at high frequency the effective cross section of the wire is narrower than at DC.
Fro example skin depth at 100 kHz is 0.206 mm (0.008”), a wire more thicker than AWG26 could be a waste of copper, better use a bunch of thin wire (Litz wire) to rise the Q factor.
Answer:
to make the bace of a building more sturdy
Explanation:
example: the bace of the empire state building is stone very sturdy
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Answer:
B A and C
Explanation:
Given:
Specimen σ
σ
A +450 -150
B +300 -300
C +500 -200
Solution:
Compute the mean stress
σ
= (σ
+ σ
)/2
σ
= (450 + (-150)) / 2
= (450 - 150) / 2
= 300/2
σ
= 150 MPa
σ
= (300 + (-300))/2
= (300 - 300) / 2
= 0/2
σ
= 0 MPa
σ
= (500 + (-200))/2
= (500 - 200) / 2
= 300/2
σ
= 150 MPa
Compute stress amplitude:
σ
= (σ
- σ
)/2
σ
= (450 - (-150)) / 2
= (450 + 150) / 2
= 600/2
σ
= 300 MPa
σ
= (300- (-300)) / 2
= (300 + 300) / 2
= 600/2
σ
= 300 MPa
σ
= (500 - (-200))/2
= (500 + 200) / 2
= 700 / 2
σ
= 350 MPa
From the above results it is concluded that the longest fatigue lifetime is of specimen B because it has the minimum mean stress.
Next, the specimen A has the fatigue lifetime which is shorter than B but longer than specimen C.
In the last comes specimen C which has the shortest fatigue lifetime because it has the higher mean stress and highest stress amplitude.