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HELP HELP!! some question related to my homework pls help~

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anzdyy

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2)The coil of a 300V moving iron voltmeter has a resistance of 500Ω and an
inductance of 0.8H. The instrument reads correctly at 50 Hz AC supply and
takes 100-mA at full scale deflection. What is the percentage error in the
instrument reading when it is connected to 200VDC supply?


3)A 250V moving-iron voltmeter takes a current of 0.1A when it is
connected to a 250VDC supply. The coil has an inductance of 0.5H. Determine
the error in the reading when the meter is connected to a 250V, 50Hz AC supply,
assuming that the voltmeter reads correctly at DC supply.




hi.. i am new member i don know is it correct to post it here if is wrong pls tell me.. thx alot... ok.. up there is the questions.. i ady have the solution i will upload it pls kindly try to see for me... y this two is almost the similiar question but question 2 is using V,voltage to find while question 3 is using I, current to find.. thx for the help...
 

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where is nigel? usually he would put a stop to that kind of jargon. haven't seen any replies from him in a while.
 
Your images are 2500 x 3500 pixels. You'll have to wait till someone gets a high enough resolution screen so they will fit.
 
I only checked your first answer and it looks fine to me. The only error I can see is you can't separate the reactance into w²L², it has to be (wL)². You state the equation wrong but have done the calculations correctly.

Mike.
 
Pommie said:
I only checked your first answer and it looks fine to me. The only error I can see is you can't separate the reactance into w²L², it has to be (wL)². You state the equation wrong but have done the calculations correctly.

Mike.


but my doubt is y the first question is using V,voltage to calculate the error while in question 2 is in I, current, ampere to calculate the error. thanks for the help..
 
anzdyy said:
but my doubt is y the first question is using V,voltage to calculate the error while in question 2 is in I, current, ampere to calculate the error. thanks for the help..

You can calculate it either way. Try redoing the first question but work out the currents involved and you will get the same error value. BTW, your second question looks correct as well.

Mike.
 
Pommie said:
You can calculate it either way. Try redoing the first question but work out the currents involved and you will get the same error value. BTW, your second question looks correct as well.

Mike.

oh ya y i din think of this.. thanks.. will try do myself
 
Pommie said:
You can calculate it either way. Try redoing the first question but work out the currents involved and you will get the same error value. BTW, your second question looks correct as well.

Mike.
i tried but i cant get it how how?? teach me
 
I can't understand how you can calculate what you posted in your first post and not be able to calculate the same using current. You simple compare V/R with V/Z.

Was what you posted your work?

Mike.
 
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