Exercises - Inductivity at AC voltage

Inductance connected to alternating voltage – exercises

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How can you measure the impedance of a coil?

 You connect the coil to DC voltage, measure current and voltage and calculate the impedance according to Ohm’s law.

 In order to determine the impedance, the wire resistance, i.e. the ohmic resistance of the coil, must first be determined. 

 The coil is connected to an AC voltage of known frequency. You measure the current and the active power with a power meter and calculate the impedance from the measured values.

 The coil is connected to an AC voltage of known frequency, the current and voltage are measured and the impedance is calculated according to Ohm’s law.

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In which circuit does the output voltage V2 increase as the frequency of the sinusoidal input voltage V1 increases?

Inductance connected to alternating voltage – exercises

 Circuit 1

 Circuit 2

 Circuit 4

 Circuit 3

 Circuit 5

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A relay labeled V~ = 12 V is accidentally connected to 12 V DC. What will happen?

 The relay coil will heat up too much due to the excessive current and the relay will be damaged.

 The relay will not function because the current will be too small.

 The relay will operate normally because the RMS value is the same for 12V AC as it is for 12V AC.

 The relay will hum, but otherwise perform its function normally.

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Exercise 1 

An ideal coil with L = 35 mH is connected to an AC voltage with a frequency of f = 50 Hz. How big is the inductive reactance X_L?

Exercise 2

An ideal coil with a reactive resistance of 6.3 kΩ is connected to a frequency of 60 Hz. Determine the inductance of the coil.

Exercise 3

A real coil has an ohmic resistance (wire resistance) and a reactance. To determine these two resistances, the coil (see measuring circuit) is connected to a DC voltage of 30 V and in the following to AC voltage of 50 V / 50 Hz. The current is 2.5 A each.

Real world Inductor - how to determine the ohmic resistance and the Impedance

Determine

- The ohmic resistance R and the inductive reactance Xbl at 50 Hz
- The inductance L
- The phase shift angle at AC voltage.