SSC JE 2013 electrical question paper with solution

Explanation:

Explanation:

An LC circuit, also called a resonant circuit, tank circuit, or tuned circuit is an electric circuit consisting of an inductor, represented by the letter L, and a capacitor, represented by the letter C, connected together in Parallel.

Explanation:

• Instantaneous power is the power of the object at any instant of time, in general, it is defined as p(t) = v(t) x  i(t)
• In a single-phase ac circuit, the instantaneous power to a load is of pulsating nature. Even at the unity power factor, the instantaneous power is always less than the unity
• For a sinusoidal signal,  the voltage swings through zero volts twice a cycle, so the instantaneous power is zero two times per cycle.
• If the load has both resistance and reactance, then the current, and voltage swings through zero twice a cycle, with different phase angle, and thus the instantaneous power will swing through zero 4 times a cycle.
• Instantaneous power is positive for one part of the cycle and negative for another part of the cycle if there is both resistance and reactance in the circuit. then there will be one negative for voltage and one negative for current thus instantaneous power will have two negative per cycle for a single-phase R-L series circuit.

Explanation:

• The Q factor is a parameter that describes the resonance behavior of an underdamped harmonic oscillator (resonator).
• In an ideal series RLC circuit, and in a tuned radio frequency receiver (TRF) the Q factor is: 1/R√L/C
• The larger the series resistance, the lower the Q factor.

Explanation:

Active power = 200 x 30 + 40 x10 =6400 W

Reactive Power = 200 x 10 – 40 x 30 = 800 VAR 

Explanation:

Norton’s theorem illustrates that a network consists of  several voltage sources, current sources, and resistors with two terminals, which is electrically equivalent to an ideal current source ” I_NO” and a single parallel  resistor, R_NO

Answer 4. 14 Ω

From the circuit diagram 

e = V – 10i

r = e/i 

= V/i -10

On differentiating

dr = dv/di -10

= 12/0.5 – 10 = 14 Ω

Answer.1. 50 Ω at a power factor of 0.6 lead

Explanation:

For maximum power transfer

Z_L = Zs* = 30 – j40

Apparent power

Zs² = 30² + 40²

Zs = 50 Ω

Power factor = Real power/ Apparent power

CosΦ = 30/50 = 0.6 leading

 A leading power factor signifies that the load is capacitive, as the load “supplies” reactive power, and therefore the reactive component  Q is negative as reactive power is being supplied to the circuit.

Answer.3. 

Explanation:

Speed torque characteristic is also called a mechanical characteristic. From the characteristics of the DC series motor, it can be found that when speed is high, torque is low, and vice versa.

Explanation:

1. The speed-torque characteristics is graph of DC motor.
2. Open circuit characteristic is also known as the magnetic characteristic or no-load saturation characteristic. it’s a graph plotted between emf induced and excitation is given ( field current ) at no load. This gives us an idea of how the dc machine is going to behave in certain field current.
3. In power engineering & electrical engineering, the V curve is the graph showing the relation of armature current as a function of field current in synchronous machines. The purpose of the curve is to show the variation in the magnitude of the armature current as the excitation voltage of the machine is varied.
4. The circle diagram is the graphical representation of the performance of the electrical machine[1][2][3] drawn in terms of the locus of the machine’s input voltage and current.[4] The circle diagram can be drawn for alternators, synchronous motors, transformers, and induction motors.