- #1
Asmaa Mohammad
- 182
- 7
Homework Statement
Homework Equations
The Attempt at a Solution
Solution for Q1:
Solution for Q2:
Solution for Q3:
Are they correct?
Ah, yes, This electronic edition of this exam is different from the one I have, luckily, the peak of the voltage is the only difference, I have just noticed.cnh1995 said:You have taken the peak emf to be 0.04V while the question says it is 0.4V.
As this:cnh1995 said:Also, how did you calculate the average of emf for 1/4 revolution?
The coil starts its motion from the position in which it is parallel to the field lines, I think after 3 seconds it will come back to its original position, where it has a maximum induced emf. But I can't prove this mathematically.cnh1995 said:For Q3: The frequency of emf is 1Hz. After 3 seconds, how many degrees would elapse? What is the emf at the beginning of this 3 second interval?
Right.Asmaa Mohammad said:The coil starts its motion from the position in which it is parallel to the field lines, I think after 3 seconds it will come back to its original position, where it has a maximum induced emf. But I can't prove this mathematically.
Right.Asmaa Mohammad said:The change in the flux dΦ = BA - 0 (BA is the maximum flux linkage when the coil is perpendicular to the field and 0 is flux linkage when the coil is parallel to the field lines) So the change would be (BA - 0).
The change in time dt = T/4 (Where T is period), and since T=1/f -----> dt = 1/4f
The average emf = -N dΦ/dt = -NBA* 4f
It is:cnh1995 said:So what is the general equation of emf in terms of maximum emf and θ, where θ is the angle between normal of the plane and the magnetic field?
Yes. Minus sign is optional.Asmaa Mohammad said:It is:
emf = -NBAω sinθ = (emf)max*sinθ
Isn't it same as above?Asmaa Mohammad said:emf = (emf)max sinθ
I meant it will be like this:cnh1995 said:Isn't it same as above?
No, in this equation we should use pi = 180, and I have already used this equation in solution for Q3, look again!cnh1995 said:So you are confused between when to take pi=180 and pi=3.14?
So, when time passes, (θ = 90 -ωt) in the case we have the problem here,cnh1995 said:At t=0, θ=90°. Therefore θ=90°-ωt and hence, θ=90°-2πft.
This is not correct in your #7. The emf in this case will ve zero.Asmaa Mohammad said:a coil starts its motion from the position it is perpendicular to the field lines, the maximum induced emf in it
You can use θ=90-ωt in #7 as well. At t=0, θ=90°, which is correct since θ is the angle between normal and the magnetic field, which is 90° when the coil is parallel to the field.Asmaa Mohammad said:So, when time passes, (θ = 90 -ωt) in the case we have the problem here,
but for the case in the problem mentioned in #7, it will be like this:
at t=0, θ=0.
cnh1995 said:You have taken the peak emf to be 0.04V while the question says it is 0.4V.
Also, how did you calculate the average of emf for 1/4 revolution?
Solution for Q2 looks fine, but you should take the peak emf to be 0.4V.
For Q3: The frequency of emf is 1Hz. After 3 seconds, how many degrees would elapse? What is the emf at the beginning of this 3 second interval?
cnh1995 said:You have taken the peak emf to be 0.04V while the question says it is 0.4V.
Also, how did you calculate the average of emf for 1/4 revolution?
Solution for Q2 looks fine, but you should take the peak emf to be 0.4V.
For Q3: The frequency of emf is 1Hz. After 3 seconds, how many degrees would elapse? What is the emf at the beginning of this 3 second interval?
EMF stands for electromotive force, which is the voltage induced in a conductor when it moves through a magnetic field. In the case of a coil rotating in a magnetic field, the changing magnetic field causes an EMF to be induced in the coil.
The average EMF in a coil rotating in a magnetic field is calculated by dividing the total change in magnetic flux by the time taken for that change to occur. This can be represented by the equation E = ΔΦ/Δt, where E is the average EMF, ΔΦ is the change in magnetic flux, and Δt is the time taken.
The average EMF in a coil rotating in a magnetic field can be affected by the strength of the magnetic field, the speed of rotation, the number of turns in the coil, and the size and shape of the coil. Additionally, the type of material used for the coil and the presence of any external resistance can also impact the average EMF.
The direction of rotation of the coil does not affect the average EMF in a coil rotating in a magnetic field. This is because the induced voltage is determined by the rate of change of the magnetic field, not the direction of rotation. However, the direction of rotation can affect the polarity of the induced voltage.
The average EMF in a coil rotating in a magnetic field is important in applications such as generators, where it is used to generate electricity. It is also a crucial concept in understanding the principles of electromagnetic induction, which has numerous practical applications in industries such as power generation, transportation, and communication.