AC DC Bridges Questions and Answers

Answer-1: A bridge circuit is a type of electrical circuit in which two circuit branches (usually in parallel with each other) are "bridged" by a third branch connected between the first two branches at some intermediate point along them.

Answer-2: The bridge circuit is useful in measuring impedances (resistors, capacitors, and inductors) and in converting signals from transducers to related voltage or current signals.

Answer-3: The bridge circuit is balanced when the output read by the meter is zero or minimum. In this condition the voltages on both sides of the meter are identical.

Answer-4: A bridge circuit that is excited by DC source is known as DC Bridge.

Answer-5: A bridge circuit that is excited by an AC source is known as an AC Bridge.

Answer-6: A resistance bridge (for AC or DC) would have four resistors and an ohmmeter. The value of two of the resistors is known precisely, and one of the resistors is variable with a clearly marked scale. The fourth resistor is the one being measured. If the variable resistor is turned until the meter reads zero, the value of the unknown resistor can be read off the scale.

Answer-7: Capacitors are devices that are used with AC circuits but they do not work with DC circuits. Capacitors affect AC circuits by shifting the relationship between the voltage and current cycles. For a capacitance measuring bridge the setup is exactly the same as for a resistance bridge except at least one of the four components is capacitor.

Answer-8: Inductors are the devices that are used with AC circuits but they do not work with DC circuits. Inductors affect AC circuits by shifting the relationship between the voltage and current cycles. For an inductor measuring bridge the setup is exactly the same as for a resistance bridge except at least one of the four components is inductor. With inductor bridges you must take care that the inductors are physically separated because inductors work with magnetism and if they are physically close together the magnetic fields can interact.

Answer-9: There are numerous AC bridge circuits, the more widely known of which are as follows:
1) Resonance Bridge
2) Schering Bridge
3) Hay Bridge
4) Owen Bridge
5) Maxwell Bridge
6) Andersons Bridge
7) Wien Bridge

Answer-10: A Resonance Bridge is an AC bridge circuit used for measuring an unknown inductance, an unknown capacitance, or an unknown frequency, by balancing the loads of its four arms.

Answer-11: A Schering Bridge is a bridge circuit used for measuring an unknown electrical capacitance and its dissipation factor.

Answer-12: The dissipation factor of a capacitor is the the ratio of its resistance to its capacitive reactance.

Answer-13: A Hay Bridge is an AC bridge circuit used for measuring an unknown inductance by balancing the loads of its four arms, one of which contains the unknown inductance.

Answer-14: An Owen Bridge is an AC bridge circuit used for measuring an unknown inductance by balancing the loads of its four arms, one of which contains the unknown inductance.

Answer-15: A Maxwell Bridge, also known as the Maxwell-Wien Bridge, is an AC bridge circuit used for measuring an unknown inductance by balancing the loads of its four arms, one of which contains the unknown inductance.

Answer-16: In Andersons bridge, the self-inductance of an inductor is measured in terms of a standard capacitor.

Answer-17: Wien Bridge in its basic form is designed to measure frequency by balancing the pots of its reactive arms. It can also be used for the measurement of an unknown capacitor by balancing the loads of its four arms with great accuracy.

Answer-18: The two AC Bridges which are frequency independent are:
1) Maxwell Bridge
2) Owen Bridge