Consider an Thin Conducting Rod of Length L which start's Rotating about an fixed Point P(L,0) in X-Y plane. Initially Rod is on X-axis at an distance of L from origin.(As shown)
There is an infinitely long wire on entire Y-axis. And current is flowing Through this wire is I 0
This Rod is rotated By an external agent with Constant angular velocity ω . Then Find the Magnitude of Motional EMF develop between the Point 'P' and centre of the rod at the instant when rod is rotated by an angle θ = 6 0 0
Details and Assumptions
∙ Long wire and Conducting Rod are Placed in X-Y plane.
∙ Rod is Rotated By an external agent so that it can definitely move with constant angular velocity.
∙ EMF means electro motive Force.
Use following data
∙ I 0 = 4 × 1 0 7 A m p . ∙ ω = 4 r a d / s ∙ L = 4 m .
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Here I used The Fact the magnetic field due to wire at an distance of x will be B = 2 π x μ 0 I 0 .
And also If an rod of length 'l' moving with velocity 'v' then emf developed in it will be = B l v .
I got the same answer but was marked incorrect. I sent the same as clarification also . It said it accepts only integer answers
I have updated the answer to 13.7505.
Those who previously entered 13 or 14 have been marked correct.
How did you integrate?
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\Ep P 0 = ∫ r = 0 r = L / 2 2 π ( L + r cos θ ) μ 0 I 0 ω r ( d r ) \Ep P 0 = 2 π μ 0 I 0 ω ∫ r = 0 r = L / 2 L + 2 r r ( d r ) ( ∵ cos 6 0 = 1 / 2 ) \Ep P 0 = π μ 0 I 0 ω ∫ r = 0 r = L / 2 2 L + r 2 L + r − 2 L ( d r ) \Ep P 0 = π μ 0 I 0 ω ∫ r = 0 r = L / 2 ( 1 − 2 L + r 2 L ) ( d r ) \Ep P 0 = π μ 0 I 0 ω ( [ r − 2 L + r 2 L ln ( 2 L + r ) ] 0 L / 2 ) \Ep P 0 = 4 π cos θ μ 0 I 0 ω L ( 1 − cos θ 1 ln 1 6 2 5 ) .
Hopes this helps You ! @Tushar Gopalka
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Bro how to integrate!! Hope this is correct dE=uiwxdx/π(2L+x) How to integrate this
General solutions is given by 2 π cos θ μ 0 i ω ( l − cos θ a ( ln ( a a + l cos θ ) ) ) W h e r e : a = D i s t a n c e o f p i v o t f r o m w i r e l = l e n g t h o f r o d θ = a n g l e m a d e b y r o d w i t h h o r i z o n t a l ω = A n g u l a r f r e q u e n c y i = C i r r e n t i n w i r e
I also wrote the exact same integral eqn but I also took the component of the element dx i.e. (dxsin(theta)) And I think we SHOULD take the element or else the integral will be wrong. By the way my answer was coming out to be 11.91( by taking the component of dx)
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Let at any Time t=t rod is rotated by an angle ' θ ' So Consider an element of length 'dr' which is at an distance of 'r' from the point of Pivot ( Point P ).
Distance of This element from the wire is
x = L + r cos θ .
Now emf induced between Point P and Centre O is :
\Ep P 0 = ∫ r = 0 r = L / 2 2 π ( L + r cos θ ) μ 0 I 0 ω r ( d r ) \Ep P 0 = 2 π μ 0 I 0 ω ∫ r = 0 r = L / 2 L + 2 r r ( d r ) ( ∵ cos 6 0 = 1 / 2 ) \Ep P 0 = π μ 0 I 0 ω ∫ r = 0 r = L / 2 2 L + r 2 L + r − 2 L ( d r ) \Ep P 0 = π μ 0 I 0 ω ∫ r = 0 r = L / 2 ( 1 − 2 L + r 2 L ) ( d r ) \Ep P 0 = π μ 0 I 0 ω ( [ r − 2 L + r 2 L ln ( 2 L + r ) ] 0 L / 2 ) \Ep P 0 = 4 π cos θ μ 0 I 0 ω L ( 1 − cos θ 1 ln 1 6 2 5 ) .