Electronics and Communication Engineering - Measurements and Instrumentation

21.
Insertion of a dielectric material between the plates of an air capacitor
increases the capacitance
decreases capacitance
has no effect an capacitance
increases breakdown voltage
Answer: Option
Explanation:

.


22.
Two ammeters A and B are connected in parallel in a circuit carrying 100 A. Their resistances are 0.8 mΩ. Their readings will be.
55.56 and 44.44 A respectively
44.44 A and 55.56 A respectively
60 A and 40 A respectively
40 A and 60 A respectively
Answer: Option
Explanation:

.


23.
In figure, Za = 100∠50°, Zb = 300∠-90° and Zc = 200∠0°. For balanced condition, Zd will be
600∠ - 40°
600∠140°
600∠ - 140°
150∠140°
Answer: Option
Explanation:

.


24.
In household energy meters the flux of series magnet is in phase with current but the flux of shunt magnet lags the voltage by 88°. The reading of energy meters
will be correct
will have a negative error
will have a positive error
may have positive or negative error
Answer: Option
Explanation:

Since angle is less than 90°, reading will be less. Therefore error is negative and correction is positive.


25.

Assertion (A): A universal RLC bridge has a battery and also a high frequency ac source.

Reason (R): RLC bridge uses a Wienbridge arrangement for measuring capacitance.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true R is false
A is false R is true
Answer: Option
Explanation:

Modified De sauty bridge is used to measure capacitance.