What are the disadvantages of the Kelvin bridge?

Disadvantages. For knowing whether the bridge is balanced or no, the sensitive galvanometer is used. To obtain good sensitivity of the device, a high current is required. Manual adjustments are to made periodically when required.

Why can’t a Kelvin bridge be used for the?

Explanation: A Kelvin bridge can be used for the measurement of high Quality factor values. Due to bridge imbalance problem, Kelvin bridge can’t be used for measuring low Quality factor values.

Why is the Kelvin double bridge more accurate?

In order to avoid this problem, Kelvin’s double bridge is used. It is so constructed that the contact resistance will not come into the picture while measuring the value of low resistance. Hence, Kelvin’s double bridge greatly improves the accuracy of measurement by eliminating the effect of contact resistance.

What is the essential condition for Kelvins Double bridge?

To understand the need of Kelvin bridge we must first recognize 3 important ways to categorize electrical resistance: High Resistance: Resistance that is greater than 0.1 Mega-ohm. Medium Resistance: Resistance that ranges from 1 ohm to 0.1 Mega-ohm.

What is the condition to achieve higher sensitivity in a Kelvin bridge?

Explanation: The condition to achieve a high sensitivity in a Kelvin bridge is that the measuring current should be high enough so as to sensitize the null detector.

Which range Cannot be measured using a Kelvin bridge?

20. Why can’t a Kelvin bridge be used for the measurement of low Quality factor value? Explanation: A Kelvin bridge can be used for the measurement of high Quality factor values. Due to bridge imbalance problem, Kelvin bridge can’t be used for measuring low Quality factor values.

What is the working principle of Kelvin bridge?

The operation of the Kelvin bridge is very similar to the Wheatstone bridge, but uses two additional resistors. Resistors R1 and R2 are connected to the outside potential terminals of the four terminal known or standard resistor Rs and the unknown resistor Rx (identified as P1 and P′1 in the diagram).

What is the use of kelvins method?

Hint:Kelvin’s method determines the resistance of the galvanometer using the principle of Wheatstone bridge, which makes it easier to find the resistance since you only need to know the ratio of the lengths and not the specific value of resistance of wires.

What is the current flowing through the detector when the bridge is said to be balanced?

The bridge is said to be balanced when deflection in the galvanometer is zero i.e. no current flows through the galvanometer or in other words VB = VD.

What is the balance equation of Kelvin bridge 1 point?

Rx = R1.R3 ⁄ R2 This additional ratio arms eliminate the effect of lead and contact resistances. The important condition for this bridge balance condition is that the ratio of the resistances of ratio arms must be the same as the ratio of the resistances of the second ratio arms.

Does Kelvin bridge is used for measurement of low resistance?

Clarification: Kelvin bridge is used for the measurement of low resistances. Low resistances vary in the range of 1Ω to 10 μΩ. Clarification: As Kelvin bridge is used for the measurement of low resistance values, the accuracy of measurement of low resistances in a Kelvin bridge is of the order of ±0.05 to ±0.2 %.

What are the criteria for balance of a Kelvin bridge?

Under balance conditions there is no current through the galvanometer which means that the voltage drop between a and b, Eab is equal to voltage drops Eamd between a and c. Eq (2) is the usual working equation for the kelvin bridge.

How to understand the need of Kelvin bridge?

To understand the need of Kelvin bridge let us categorize the electrical resistances on the basis of view point of measurement: Electrical resistances are classified as follows: High Resistance: Under this category resistance is greater than 0.1 Mega-ohm. Medium Resistance: Under this category resistance is ranging from 1 ohm to 0.1 Mega-ohm.

What is the unknown resistance value of Kelvin double bridge?

The unknown resistance value can be obtained from the two arms of Kelvin double bridge, typically, it measures 1- 0.00001 ohm with an accuracy ± 0.05% to ±0.2%. A bridge is an electrical circuit, which is used in Labourites for measuring various parameters.

What is the effect of load and contact resistance on Kelvin bridge?

There is no effect of load and contact resistance in the Kelvin bridge since the bridge is independent of load and contact resistance. 7). What is the accuracy of Kelvin Double Bridge? The unknown resistance value can be obtained from the two arms of Kelvin double bridge, typically, it measures 1- 0.00001 ohm with an accuracy ± 0.05% to ±0.2%.

Which wire is eliminated with the Kelvin bridge?

The final equation is the same as the balanced Wheatstone Bridge, which shows that connecting lead wire has been eliminated by connecting the galvanometer at point ‘b’. is eliminated with the kelvin bridge.