Question:
In Part-20 Question No-2(b), Why you have taken V=vm cos(wt @)
Answer:
In Part-20 Question No-2(b), Why you have taken V=vm cos(wt @)
As said in the video part 20, Class 12, Alternating current, the sin and the cos wave function over time is the same representation when viewed graphically
It depends on the easiness to solve the problem, whether you take sin or cos. Mostly, as we know sin 0 is 0 and cos 90 is 0, our choice of assumption of equation could be based on this.
The current and the voltage have a phase difference of ɸ. Hence, the equations can be V = Vm cos ωt, I = Im cos (ωt - ɸ) OR V = Vm sin ωt, I = Im sin (ωt - ɸ)
- Now consider t = 0 in the case V = Vm cos ωt, I = Im cos (ωt - ɸ) then we get V = Vm as cos 0 is 1
- But if we had considered t = 0 in the case V = Vm sin ωt, I = Im sin (ωt - ɸ) then we get V = 0 as sin 0 is 0 – From this no specific interpretation can be drawn.
As t = 0, V = 0 does not give us anything to interpret, it is better to consider the case of cos function where t= 0, V = Vm is easy to interpret This fact is emphasised in the video also.
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