EE3251 Electric Circuits Analysis Important Questions

EE3251 Electric Circuits Analysis Important Questions

Unit 1

1.  Determine the node to reference voltages for the circuit shown in Fig. 1. 
   

   

2. Obtain a relationship between root mean square value and peak value of a sinusoidal signal.
3. Find the value of ‘Vo’ in the circuit shown in Figure 6. 
   

   

4. Find the range of ‘Rin’ for the circuit shown in Figure 7. 
   

   

Unit 2

1. Find the Norton equivalent circuit for the circuit shown in Fig.2 at terminals a-b. 
   

   

2. Obtain the equivalent resistance Rab for the circuit shown in Fig. 3 using star-delta conversion. 
   

   

3. Find the Norton’s equivalent across the terminals ‘a’ and ‘b’ for the circuit shown in Figure 8. 
   

   

4. Find ‘v’ using superposition theorem for the circuit shown in Figure 9. 
   

   

Unit 3

1. A circuit consists of a resistor connected in series with a 0.5 µF capacitor and has a time constant of 12 ms. Determine
   (i) the value of the resistor,
   (ii) the capacitor voltage 7 ms after connecting the circuit to a 10 V supply.
2. A coil of inductance 0.04 H and resistance 10 2 is connected to a 120 V, d.c. supply. Determine (i) the final value of current, (ii) the time constant of the circuit, (iii) the value of current after a time equal to the time constant from the instant the supply voltage is connected, (iv) the expected time for the current to rise to within 1% of its final value.
3. In the circuit shown in Figure 10, the battery voltage is applied for a steady state period. Obtain the complete expression for the current after closing the switch ‘K’. 
   

   

4. A capacitor of 5 microfarad is being charged to 10 V is connected to a resistance of 10 ko and is allowed to discharge through it by closing a switch ‘K’. Find the expression of discharging current.

Unit 4

1. A series circuit comprises a 10 2 resistance, a 5 µF capacitor and a variable inductance L. The supply voltage is 206 0° volts at a frequency of 318.3 Hz. The inductance is adjusted until the p.d. across the 10 Ω resistance is a maximum. Determine for this condition (i) the value of inductance L, (ii) the p.d. across each component and (iii) the Q-factor.
2. Determine the relationship between the resonance frequency and the half power frequencies of a series resonating circuit.
3. Following data refers to two coupled coils 1 and 2 (Figure 11). Ф11=0.5 mWb, 120.3 mWb, N₁100 turns, N2500 turns; i₁=1 A. Find coefficient of coupling, inductances L1, L2 and M.  
   

   

4. A coil of inductance 5 mH and resistance 10 2 is connected in parallel with a 250 nF capacitor across a 50 V variable-frequency supply. Determine (i) the resonant frequency, (ii) the dynamic resistance, (iii) the current at resonance, and (iv) the circuit Q-factor at resonance.

Unit 5

1. A balanced, three-wire, star-connected, 3-phase load has a phase voltage of 240 V, a line current of 5 A and a lagging power factor of 0.966. Draw the complete phasor diagram and also write the procedure to construct the phasor diagram.
2. Explain the two wattmeter method of measuring three phase power with neat circuit connections.
3. A balanced three phase star connected load is connected across a 11 kV, 50 Hz, three phase supply. If the load consumes 150 kW and takes a leading current of 100 A, find the circuit constants of the load on per phase basis.
4. Three identical resistances are connected in a star fashion, against a balanced three phase voltage supply. If one of the resistances is removed, calculate the reduction in power.