11. Calculate the equivalent resistance when three resistances are connected in a series of values 8 Ω, 3 Ω, and 1 Ω.
A. 12 Ω
B. 18 Ω
C. 15 Ω
D. 16 Ω
Answer: A
When three resistances are connected in series their equivalent resistance is equal to the sum of the individual resistances.
Req=R1+ R3+R2=12 Ω.
12. Calculate the active power in an inf Ω resistor with 0 current flowing through it.
A. inf MW
B. 4.44 MW
C. 12 MW
D. 6.18 MW
Answer: A
The resistor is a linear element. It only absorbs real power and dissipates it in the form of heat. The voltage and current are in the same phase in the case of the resistor so the angle between V & I is 0°.
P=I2R=0×0×inf=inf MW.
13. When 15 A current flows into the positive terminal of voltage source 60 V. Calculate the power delivered by the source.
A. -900 W
B. 936 W
C. -943 W
D. 950 W
Answer: A
When the current enters the positive terminal of an element it will always absorb the power and when the current leaves the positive terminal it will deliver the power.
Power delivered is -15×60=-900 W.
14. Source transformation is not valid for ___________
A. Ideal voltage source
B. Ideal current and voltage source
C. Practical voltage source
D. Practical current source
Answer: B
Source transformation is not valid for an ideal current and voltage source. The internal resistance for ideal voltage and current source is zero due to which source transformation is not valid.
15. Regenerative braking is not possible in a series motor.
A. True
B. False
Answer: A
In regenerative braking, the motor acts as a generator. The back emf is more than the terminal voltage in the case of regenerative braking.
16. Regenerative is the best electrical braking among all braking techniques.
A. True
B. False
Answer: A
In regenerative braking, the power is fed back to the source from the battery. The kinetic energy of the motor shaft is converted into electrical energy.
17. Full form of SCIM.
A. Squirrel cage induction motor
B. Solid cage induction motor
C. Square cage induction motor
D. Squirrel cage inverter motor
Answer: A
SCIM stands for squirrel cage induction motor. SCIM rotor is made up of aluminum, and copper bars. There are no armature conductors involved in it.
18. Wound rotor induction motor has better ________ characteristics than Squirrel cage induction motor.
A. Starting
B. Running
C. Modified
D. Quasi-state
Answer: A
A wound rotor induction motor has better starting characteristics because external resistance can be connected to it using slip rings to start the motor. In the case of SCIM, no external resistance can be connected to the rotor side.
19. All circuits are always _________
A. Networks
B. Resistors
C. Capacitors
D. Inductors
Answer: A
The network is defined as the interconnection of electrical elements that may or may not has a closed path. The circuit is defined as the interconnection of an element that must have at least one closed path. All circuits are always networks but vice-versa is not true.
20. The dead network does not have any _________
A. Dependent source
B. Independent source
C. Resistor
D. Capacitor
Answer: B
In the case of the dead network, there are no independent sources available in the electrical circuit. The Thevenin voltage of the circuit is zero because no force is available to drive the current in the circuit.
