How Do You Calculate Voltage Drop in a Series Inductor and Resistor Circuit?

AI Thread Summary
In a series circuit with a 680Ω resistor and a 98.2Ω inductor, the supply voltage is 13.2V, and the circuit current is 8.1mA. The voltage drop across the inductor's windings is calculated using Ohm's Law, resulting in 0.8V, while the voltage across the resistor is 5.5V. Adding these values gives a total voltage drop of 6.3V. To find the voltage across the pure inductance, a scaled phasor diagram is suggested, involving drawing specific lengths to represent the voltages. The discussion concludes with a user expressing gratitude for the assistance received.
TommyJBrown
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1. Inductor & Resistor connected in series
A circuit comprising of an Inductor & Resistor connected in series.
The values are:
R1 resistor Value 680Ω
Resistance of the Inductor's Windings: (R of L) 98.2Ω
Supply Voltage: 13.2V
Circuit Current: 8.1mA
Supply Freq: 50Hz
Voltage across the resistor R1 5.5V
Voltage across the inductor 10.4V

Questions:
1. Use Ohm's Law to find the voltage dropped across the resistance of the inductor's windings (R of L)

2. Add this value to the voltage dropped across the resistor R1

3. Draw a scaled phasor diagram of the resistive voltage and the supply voltage, to find the voltage dropped across the pure inductance.

My solution so far:

1. = 8.1mA * 98.2Ω = 0.8V
Voltage dropped across R1 = 8.1mA * 680Ω = 5.5V

2. = 0.8V + 5.5v = 6.3V

3. This is where I get stuck

Can anyone Help!
 
Last edited:
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Draw a line AB of length 13.2 cm, which represents the supply voltage. From A draw an arc of length 5.5 cm, which represents voltage across R. From B draw an arc of length 10.4 cm, which represent the voltage across L.. Find the point of intersection C. Join AC. Drop a perpendicular from B to AC produced. The length of the perpendicular is the voltage across the pure inductance.
 
Thanks rl bahat.

That works fine... I couldn't see the wood for the trees!
Once again
Cheers
Tommy
 
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