# Electrical Measurements Questions and Answers – Capacitance Comparison Bridge

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Capacitance Comparison Bridge”.

1. In a capacitance bridge, the arms are _________
a) resistive
b) capacitive
c) inductive
d) mixture of resistance, capacitance and inductance

Explanation: The capacitance bridge is mainly used for the measurement of unknown capacitance. The ratio arms in a capacitance bridge are resistive in nature.

2. How is the bridge balanced?
a) using resistance R1
b) using resistance R3
c) through capacitance C3
d) through capacitance Cx

Explanation: Bridge balance is obtained by varying the resistance R3. At balance we get the value of the unknown resistance as Rx = R1 R3R2.

3. Impedance Z4 consists of _________
a) resistance Rx
b) capacitance Cx
c) combination of capacitance Cx and resistance Rx
d) consists of a detector

Explanation: Ratio arm Z4 consists of the unknown impedance. Impedance Z4 consists of capacitance Cx in series with a leakage resistance Rx.

4. Impedance Z3 consists of_________
a) resistance R3
b) capacitance C3
c) vibration galvanometer
d) capacitance C3 in series with resistance R3

Explanation: Impedance usually refers to the combination of resistance and either capacitance or inductance. As we are considering the case of capacitance measurement, impedance Z3 comprises capacitance C3 in series with resistance R3.

5. Unknown capacitance value is obtained by _________
a) comparison with standard
b) using a tuned detector
c) using capacitance of other ratio arms
d) using a vibration galvanometer

Explanation: Tuned circuit is used for detecting balance condition. Vibration galvanometer is used for the same purpose. Unknown value of capacitance is obtained by comparing it with a standard value.
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6. Unknown resistance is obtained by using which of the following relation?
a) Rx = $$\frac{R_1 R_3}{R_2}$$
b) Rx = $$\frac{R_2 R_3}{R_1}$$
c) Rx = $$\frac{R_2 R_1}{R_3}$$
d) Rx = $$\frac{R_2}{R_1}$$

Explanation: The value of the unknown resistance is obtained by using the relation
Rx = $$\frac{R_2 R_3}{R_1}$$
at balance condition.

7. Unknown capacitance is found by using which of the following relation?
a) Cx = $$\frac{C_3 R_2}{R_1}$$
b) Cx = $$\frac{C_3}{R_2}$$
c) Cx = $$\frac{C_3 R_1}{R_2}$$
d) Cx = $$\frac{R_1}{R_2}$$

Explanation: The value of unknown capacitance is found using the relation Cx = $$\frac{C_3 R_1}{R_2}$$ at balance condition.

8. Actual balance condition can be obtained by _________
a) varying R1
b) varying R3
c) varying R2
d) varying R1 and R3

Explanation: Resistances R1 and R3 are variable, while resistance R2 is fixed. By varying the resistances R1 and R3, we get the actual balance condition.

Sanfoundry Global Education & Learning Series – Electrical Measurements.