Why Current Decreases When Inductance or Inductive Reactance Increases?

In Inductive Circuit, Why the Circuit Current (I) Decreases, When Inductance (L) or Inductive reactance (X_L) Increases?

Another question from electrical and electronics engineering interviews question and answers series.

Explain the statement that ” In an Inductive circuit, when Inductance (L) or inductive reactance (X_L) increases, the Circuit Current (I) decreases“.

Related Question: Why Current Increases When Capacitance Increases or Capacitive Reactance Decreases?

Explanation:

We know that in DC circuits:

I = V / R,

But in case of AC circuits:

I = V / Z

Where “total resistance of AC circuits = Impedance = Z = √ (R² + (X_L – X_C²)”

In case of Inductive circuit:

• Z = √ (R² + X_L²)
• I = V / X_L or I = V / Z

It shows that in inductive circuit, Current is inversely proportional to the inductive reactance as well as inductance “L” as inductance and inductive reactances “X_L” are directly proportional to each others.

• Related Question: According to Ohm’s Law, I ∝ V, But I ∝ 1/V in Power Equation. How do you Explain?

Let’s check with an example to see how current reduced by inductive reactance.

When Inductance = 0.02 H

Suppose an inductive circuit where:

• Inductance = L = 0.02 Henry
• Voltage = V = 220 V
• Resistance = R = 10 Ω
• Frequency = f = 50 Hz

To find the inductive reactance;

X_L = 2πfL

X_L = 2 x 3.1415 x 50 x 0.02

X_L = 6.28 Ω

Now circuit impedance:

Z = √ (R² + X_L²)

Z = √ (10² + 6.28²)

Z = 11.8 Ω

Finally, current in inductive circuit:

I = V / Z

I = 220 V / 11.8 Ω

 I = 18.64 A 

Related Questions:

• Why Power Factor Decreases When Inductance or Inductive Reactance Increases?
• Why Power Factor Decreases When Capacitive Reactance Increases or Capacitance Decreases?

When Inductance = 0.04 H

Now we increased the Inductance (L) of inductor form 0.02 H to 0.04 H,

V = 220 V, R = 10 Ω, L = 0.04 H, f = 50 Hz.

X_L = 2πfL= 2 x 3.1415 x 50 x 0.04 = 12.56 Ω

Z = √ (R² + X_L²) = √ (10² + 12.56²) = 16.05 Ω

I = V / Z = 220 V / 16.05 Ω

 I = 13.70 A 

Related Questions:

• In a Capacitive Circuit, Why the Current Increases When Frequency Increases?
• In an Inductive Circuit, Why the Current Increases When Frequency Decreases?

Conclusion:

We can see that, When inductance (L) was 0.02 Henry, then circuit current were 18.64 A,

But when circuit inductance increased from 0.02 H to 0.04 H, then the current decreased from 18.64 A to 13.70 A.

Hence proved,

In an inductive circuit, when inductive reactance X_L increases, the circuit current decreases and vice versa.

In oral or verbal,

• Inductive reactance is a kind of resistance. When resistance increases, the circuit current decreases and vice versa.
• Inductance is directly proportional to the inductive reactance

L ∝ X_L

• Current is inversely proportional to the inductance and inductive reactance.

I ∝ 1/L     and     I ∝ 1/X_L

Related Questions/Answers:

• Why Flux in Primary and Secondary Winding is Always Equal?
• Why the reactance of a system under fault condition is low and faults currents may raise to the dangerously high value?
• Why Inductive Reactance (X_L In DC Supply Is Zero (0)?