# Analogue Circuits Question -- AC and DC currents through a coil

• IronaSona
In summary, the questioner incorrectly specifies lower case units, without a space; 100v, 250w, 50hz.The answer for the capacitor case looks ok, though I haven't check the arithmetic operations.
IronaSona
Summary:: .

Hi ,so am currently doing homework , and was wondering if anyone could tell me if i have done my calculations correctly ,because am not 100% sure that i have answer to those 2 questions correctly .If i have went somewhere wrong if you could tell me where and how i could fix it ,that would be great. Thank you.

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IronaSona
You are a bit more consistent than the examiner.
The questioner wrongly specifies lower case units, without a space; 100v, 250w, 50hz.

For units named after a person, such as Volta, Watt or Hertz;
the initial should be spaced and upper case; 100 V, 250 W, 50 Hz;
while the spelled out unit should be all lower case; 100 volt, 250 watt, 50 hertz.

berkeman and IronaSona
The answer for the capacitor case looks ok, though I haven't check the arithmetic operations.

The answer for the coil contains too many typos and inconsistencies, for example you write that ##Z=\sqrt{R^2+X_L^2}## and then later you seem to imply that ##Z=X_L##.

Delta2 said:
The answer for the capacitor case looks ok, though I haven't check the arithmetic operations.

The answer for the coil contains too many typos and inconsistencies, for example you write that ##Z=\sqrt{R^2+X_L^2}## and then later you seem to imply that ##Z=X_L##.

is this better ?

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Nope you basically do the same mistake. The correct way to go is as follows:
The coil's impedance at 60hz is ##Z=\frac{140}{2}##. Use this and the equation ##Z=\sqrt{R^2+X_L^2}## to correctly determine the reactance ##X_L## at 60 hz and from that the value of L.
Then you should NOT forget the ohmic resistance of the coil when you calculate the new reactance and new impedance at 50hz

Delta2 said:
Nope you basically do the same mistake. The correct way to go is as follows:
The coil's impedance at 60hz is ##Z=\frac{140}{2}##. Use this and the equation ##Z=\sqrt{R^2+X_L^2}## to correctly determine the reactance ##X_L## at 60 hz and from that the value of L.
Then you should NOT forget the ohmic resistance of the coil when you calculate the new reactance and new impedance at 50hz

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There are still some typos but now what you do seems correct. Havent checked the arithmetic.

IronaSona

## 1. What is the difference between AC and DC currents?

AC stands for alternating current, which means the direction of the current changes periodically. DC stands for direct current, which means the current flows in one direction.

## 2. How does a coil affect AC and DC currents?

A coil, also known as an inductor, resists changes in current flow. For AC currents, a coil will cause the current to lag behind the voltage due to its inductance. For DC currents, a coil will act as a short circuit, allowing the current to flow through it without any resistance.

## 3. Can a coil be used to convert AC to DC?

Yes, a coil can be used in conjunction with other components, such as diodes, to convert AC to DC. This is known as a rectifier circuit.

## 4. How does the frequency of the current affect the behavior of a coil?

The higher the frequency of the current, the greater the inductive reactance of the coil. This means that the coil will have a greater effect on AC currents compared to DC currents.

## 5. What is the purpose of using a coil in a circuit?

Coils are commonly used in circuits to filter out unwanted frequencies, to create a magnetic field, or to store energy. They can also be used for impedance matching and voltage regulation.

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