Test: Measurement of Inductance - Electrical Engineering (EE) MCQ

Owen’s bridge is used for the inductance measurement of low Q coils.
De-Sauty’s bridge is used for the measurement of perfect capacitors.
So that both statements are true.

Heaviside bridge:

• Heaviside bridge is used to measure the mutual inductance.
• The bridge which measures the unknown mutual inductance regarding mutual inductance such type of bridge is known as the Campbell bridge.
• Mutual inductance is the phenomenon in which the variation of current in one coil induces the current in the nearer coil.
• The bridge is also used for measuring the frequency by adjusting the mutual inductance until the null point is not obtained.

Bridge is a simple closed circuit extensively used for measuring component values such as resistance, inductance, capacitance and for other derived circuit parameters directly from the component values.

Bridge circuit compares the value of unknown quantity with a known quantity.

Maxwell's bridge measures an unknown inductance in terms of known capacitance. It is advanced form of the Wheatstone bridge which works on the principle of comparison. i.e. the value of unknown inductance is determined by comparing it with the known value or standard value.

Two methods are used to determine the self-inductance of the circuit:

1. Maxwell's inductance bridge 

2. Maxwell's inductance capacitance bridge

Hay’s bridge is used for measurement of inductance of coils with high quality factor.

In a Maxwell – inductance-capacitance bridge,

Z₁Z₄ = Z₂Z₃

Where Z₁, Z₂, Z₃, Z₄ are the impedances

Given:

R₂ = 1000 Ω,

R₃ = 1000 Ω,

R₄ = R5 = 2000 Ω,

C₅ = C₄ = 1 μF

So, for bridge balance,

 L_x/C₅ = R₂R₃

L_x = R₂R₃C₅

L_x = 1000 × 1000 × 1 μ = 1 H

Also, for R_x

i.e. R_xR₅ = R₂R₃

    
So, L_x = 1H, R_x = 500 Ω

Here R₁ and L₁ are the unknown resistance and inductance of the coil.

At bridge balance condition,

Z₁Z₄ = Z₂Z₃

From the above expression, it is clear that unknown inductance (L₁) is in terms of known capacitance C₄. 

Maxwell’s inductance bridge:

In Maxwell’s inductance bridge resistance is connected in parallel with the standard capacitor. It is commonly used for measurement of Inductance of a coil having Q value in the range of (1< Q < 10).

In Maxwell’s inductance bridge resistance is connected in parallel with the standard capacitor.

Hay’s bridge:

• In Hay’s bridge, a resistance is connected in series with a standard capacitor.
• Hay’s bridge is used for the measurement of the inductance of coils with high-quality factors.

Maxwell’s inductance-capacitance bridge:

In Maxwell’s inductance bridge resistance is connected in parallel with the standard capacitor.

Maxwell’s inductance bridge:

In Maxwell’s inductance bridge resistance is connected in parallel with the standard known capacitor. It is commonly used for the measurement of the Inductance of a coil having a Q value in the range (medium) of (1< Q < 10).

In Maxwell’s inductance bridge resistance is connected in parallel with the standard capacitor.

Notes:

1) A Maxwell bridge is a modification to a Wheatstone bridge used to measure an unknown inductance (usually of low Q value) in terms of calibrated resistance and inductance or resistance and capacitance

2) Maxwell-Wien Bridge, also known as Maxwell Inductance bridge can measure unknown inductance when a known capacitance in the bridge is given.

Equations of Maxwell-Wien bridge are: