Inductive Circuit and Frequency

AI Thread Summary
In a series circuit with a resistor and an inductor, as the frequency of the supply increases, the inductive reactance also increases, leading to a decrease in current. Consequently, the voltage across the resistor increases to maintain a constant total voltage, while the voltage across the inductor decreases. The discussion highlights confusion regarding whether the circuit includes a capacitor or an inductor, emphasizing the need for clarity in circuit components. The concept of reactance is explained, detailing how it affects voltage readings in AC circuits. Overall, understanding the relationship between frequency, current, and voltage is crucial for solving the problem effectively.
ah4p
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Homework Statement



A resistor and a capacitor are connected in series to a variable frequency supply. A voltmerter is connected across the inductor and another across the resistor. The supply voltage is kept constant as frequency of supply is increased.
State and explain the changes in the readings on voltmeters across the inductor and across the resistor

Homework Equations



current is inversely proportional to frequency in an inductive circuit

V=IR

The Attempt at a Solution



I thought across the inductor V decreases since I will decrease as a result of frequency increasing

therefore to keep total V constant the V across the resistor will increase

4. Actual ANSWER

the answer however is V across resistor increases because Inductive reactance increases & Current decreases

so V across inductor decreases

I've never been taught what inductive reactance means?

can anyone explain why this is the answer
thank you very much in advance :)
my prelim is on MOnday :( and I'm so failing
 
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First phrase says R series C ... the rest talks about L ... are there all 3, or just L?
reactance "X" is a "generalized resistance" ... how much (volt-wise) does the device "react" to conducting AC current?
V(AC) = I X
for a Resistor, XR = R , no matter what the frequency is.
for a capacitor, XC = 1/ωC ... since small amount of charge collects in short time, at high frequency.
for an inductor, XL = ωL ... since the current changes more rapidly at high frequency.


You have R series L, so they have the same current;
what happens to the Resistor's voltage, if the current is limited by the inductor (at high frequency)?
 
lightgrav said:
First phrase says R series C ... the rest talks about L ... are there all 3, or just L?
reactance "X" is a "generalized resistance" ... how much (volt-wise) does the device "react" to conducting AC current?
V(AC) = I X
for a Resistor, XR = R , no matter what the frequency is.
for a capacitor, XC = 1/ωC ... since small amount of charge collects in short time, at high frequency.
for an inductor, XL = ωL ... since the current changes more rapidly at high frequency.You have R series L, so they have the same current;
what happens to the Resistor's voltage, if the current is limited by the inductor (at high frequency)?

oh it would increase since the electrons require more energy to move through it??

thanks for replying
 
ah4p said:
4. Actual ANSWER

the answer however is V across resistor increases because Inductive reactance increases & Current decreases

so V across inductor decreases
Unfortunately, this cannot be the correct answer. It is contradictory in itself. Please check whether you have transcribed this incorrectly.

You haven't answered lightgrav's question: does this problem involve a series R + C or a series R + L. You have mentioned both, probably a careless mistake due to haste, or you may be mixing up two separate questions.
 
You did not describe the position of the inductor in the circuit.
 
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