Measurements and Instrumentation

31

DC voltage of the order of a few mV can be accurately of measured by

A. PMMC voltmeters
B. moving iron voltmeter
C. null balancing potentiometer
D. electrostatic voltmeter

32

Assertion (A): The gall tinsley potentiometer is a coordinate potentiometer and has two exactly similar potentiometers.

Reason (R): An ac potentiometer may measure the unknown voltage in polar form or rectangular coordinate form.

A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true R is false
D. A is false R is true

33

Which of the following is used as detector in audio frequency ac bridges?

A. AC voltmeter
B. CRO
C. Head phones
D. Vibration galvanometer

34

An oscilloscope has an input impedance consisting of 1 M`Omega` and 20 pF is parallel. A high impedance probe connected to input of this oscilloscope has a 10 M`Omega` series resistance. This 10 M`Omega` series resistance

A. may not be shunted
B. should be shunted by 2 pF capacitor
C. should be shunted by 20 pF capacitor
D. should be shunted by 200 pF capacitor

35

Rayleigh current balance is an absolute instrument.

A. True
B. False