The stator winding of a control transformer in a synchro pair has a high impedance per phase
Statement II:
The rotor of the control transformer is cylindrical in shape.
Question 2
Statement I:
A salient-pole rotor placed in a magnetic field can produce an emf. proportional to the speed of the rotating machine because fo its variable reluctance characteristic.
Statement II:
The above device is essentially a frequency tachometer using a suitable pulse shaping circuit and an electronic counter.
Question 3
Statement I:
If a squirrel cage motor is started at full rated voltage, the power supply could be damaged.
Statement II:
For squirrel cage induction motors, starting current is high and power factor at starting is low.
Question 4
Statement I:
An induction motor always runs at a speed less than its synchronous speed.
Statement II:
Synchronous speed of induction motor depends on the frequency of supply and number of poles.
Question 5
Statement I:
Series DC motors are used for cranes and locomotives.
Statement II:
Series DC motors provide high starting torques, a requisite for such applications.
Question 6
Statement I:
Two ideal current sources with currents I1 and I2 cannot be connected in parallel
Statement II:
Superposition theorem cannot be applied to ideal current sources if these source are connected in cascade.
Question 7
A signal is band limited to 3.6 kHz and three other signals are band limited to 1.2 kHz each. These signals are to be transmitted by means of time division multiplexing. If each signal is sampled at its Nyquist rate, then the speed of the commutator (by assuming 6 samples per rotation) is
Question 8
Statement I:
When a transformer is loaded there is a change in its secondary voltage expressed as a percentage of secondary voltage on no-load, and this change is called its regulation.
Statement II:
The change in secondary voltage is due to the transformer impedance and the load current. The regulation could be zero for leading load condition.
Question 9
The phase detector circuit in the phase locked loop demodulators recognizes
Question 10
A resistance strain gauge is used to measure stress of steel which is stressed to 1200 kg/ cm2. If the gauge factor is 2.5 and the Young’s modulus of steel is 2 × 106 kg/cm2 the percentage change in resistance of the gauge is
