December 9th, 2018, 04:33 AM  #1 
Member Joined: Nov 2012 From: The Netherlands Posts: 40 Thanks: 2  wire frames as a dynamo
Hi I have the query of the following nature: In Fig. 1, a wire frame ABCD) is drawn in a homogeneous magnetic field B = 0.10 T . The points P and Q are connected to a voltmeter. Then the wire frame is mechanically driven. In this case side AD moves forward in the position shown (paper out). The wire frame has a surface of 60 cm2 and functions as a dynamo. Query 1: Find out in which direction a current flows through the wire frame during the first quarter turn of the wire frame. Figure 2 In figure 2 a graph of the flux 'phi' through the wire frame is drawn in the course of time. The flux can also be calculated by drawing up a sinus formula. Query 2 : Determine the maximum voltage of this 'dynamo'. The rotational frequency of the dynamo is reduced to half. Query 2. Sketch the corresponding (* U ind, t) graph. **where U is Indution and is subscript ind. Thus U subscript 'ind'. Give the characteristic points in the graph clearly with corresponding values. ++++++++++++++++++++++++++++++++++++++++++++++++++ ++++ can anyone give me some pointers on how to tackle this situation. some feedback on how to proceed would be of a good assistance here. Thanks in advance 
December 9th, 2018, 10:36 AM  #2  
Math Team Joined: Jul 2011 From: Texas Posts: 2,924 Thanks: 1521  Quote:
Quote:
from the sinusoid, note the period $T = 0.04 \, s$ and the amplitude is $\Phi = 0.0006 \, Wb$ ... $\Phi (t) = 0.0006\sin(50\pi \cdot t)$ $\dfrac{d \Phi}{dt} = 0.03\pi \cos(50\pi \cdot t)$ Max voltage occurs when $\dfrac{d \Phi}{dt}$ is a maximum $\implies \cos(50\pi \cdot t) = 1$ also note (for a single looped wire frame) $E = \dfrac{d \Phi}{dt}$ Quote:
How will changing the frequency to half its initial value affect the period of the graph?  
December 9th, 2018, 11:02 AM  #3 
Member Joined: Nov 2012 From: The Netherlands Posts: 40 Thanks: 2 
Thank you skeeter This will at least help me to kickstart the issue. Let me dwell into this and I fill post my side of the feedback soon. Thanks ! 
December 9th, 2018, 12:29 PM  #4 
Senior Member Joined: Sep 2015 From: USA Posts: 2,430 Thanks: 1315 
wb Skeeter, good to see you again.

December 20th, 2018, 01:49 AM  #5 
Member Joined: Nov 2012 From: The Netherlands Posts: 40 Thanks: 2 
Hi All as I had stated, I would come back and give the final feedback. (It's not me ) but my son has been able to do what was required (I think). The resolution is as here : https://i.postimg.cc/NFXNJ2pN/problms.jpg This was just for the records. Thanks 