The force between two charged particle is given by, $${\text{F}} = \frac{1}{{4\pi {\varepsilon _0}}}\frac{{{{\text{Q}}_{\text{1}}}{{\text{Q}}_{\text{2}}}}}{{{{\text{r}}^2}}},$$    where the symbols have their usual meanings. The dimensions of ∈₀ in free space in SI system are:

One single phase wattmeter operating on 230V and 5A for 5 hours makes 1940 revolutions. Meter constant in revolutions is 400. What is the power factor of the land?

A. 1

B. 0.84

C. 0.73

D. 0.65

The spring material used in a spring control device should have the following property.

A. Should be nonmagnetic

B. Most be of low temperature coefficient

C. Should have low specific resistance

D. All of the above

Why is a MISC meter not recommended for DC measurement?

A. The meter is calibrated for AC and it’s error for DC would be high

B. The meter does not respond to DC signals

C. The error is high due to hysteresis effect

D. The error is high due to eddy current effect

A moving iron ammeter may be compensated for frequency errors by

A. A shunt resistance

B. A series inductance

C. Shunt capacitance

D. Series resistance