Construction and Working

Q. A dynamometer type wattmeter responds to the

1. average value of active power
2. average value of reactive power
3. peak value of active power
4. peak value of reactive power

Q. A current transformer rated 100/5 A has magnetizing and loss components of the exciting current as 1 A and 0.6 A respectively. The secondary winding burden is purely resistive. It's transformation ratio at rated current is

1. 20.12
2. 20.20
3. 19.88
4. 20.00

Q.

A transformer has $500\mathrm{turns}$ in its primary and $1000\mathrm{turns}$ in its secondary winding. The primary voltage is $200\mathrm{V}$ and the load in the secondary is $100\mathrm{ohm}$. Calculate the current in the primary, assuming it to be an ideal transformer.

Q. The damping method used in horizontally mounted moving iron instrument is

1. Eddy current damping
2. Electro magnetic damping
3. Fluid friction damping
4. Air friction damping

Q. Electrodynamic type watt meters have large errors while measuring power in AC circuits at low power factor conditions, since the voltage across and the current through the

1. current coil are not in phase
2. current coil not in quadrature
3. pressure coil are not in phase
4. pressure coil are not in quadrature

Q. Disc in an induction type energy meter rotates in the opposite direction when

1. a large capacitor is connected on the load side
2. a large inductor is connected on the load side
3. current coil and voltage coil are wrongly connected
4. either current coil or voltage coil is wrongly connected.

Q. A moving iron ammeter has constant rate of change of inductance with respect to deflection equal to $3\mu H/degree.$ The control torque is provided by spring having spring constant equal to $4\times {10}^{-7}N-m/degree.$ If the maximum deflection of pointer is 120°, then current corresponding to this maximum deflection will be _______A.

1. 5.66

Q. An input voltage represented by waveform as shown below is applied to a true RMS meter. The reading of instrument will be_____V.(upto two decimal places)

1. 2.18

Q. In the context of a PMMC instrument, identify the correct matches:

List - I	List - II
(i) a pair of springs	(p) to provide controlling torque
(ii) aluminimum former	(q) to provide damping torque
	(r) to act as a base for the coil
	(s) to provide current into and out of the moving coil

1. (i) - (p) and (q), (ii) - (r) and (s)
2. (i) - (r) and (s), (ii) - (p) and (q)
3. (i) - (p) and (s), (ii) - (q) and (r)
4. (i) - (q) and (r), (ii) - (p) and (s)

Q. The moving coil in a dynamometer wattmeter is normally connected

1. in series with the fixed coil
2. across the supply
3. in series with the load
4. across the load

Q. Which of the given below methods is/are effective in reducing phase angle and/or ratio error in CT?

1. By turns compensation
2. By reducing the primary turns
3. By reducing the primary turns.
4. By using toroidal cores