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# Model Paper DEEE III SEM ||ELEC. CIRCUITS EE-303||

##### Time: 3 Hours                        Total marks: 80

###### PART-A                                                10 X 3=30

Instructions: 1) Answer all questions.
2) Each answer carries three marks.
3) Answer should be brief and straight to the point and shall not exceed
five simple sentences.

1. Define junction, branch and loop in circuits.
2. State the limitations of ohm’s law.
3. Define (a) cycle (b) time period (c) frequency.
4. Convert the polar form 100 /͟30° into rectangular form.
5. Define RMS value and average value.
6. A pure inductance coil taken a current of 15 amps for 200volts, 50 Hz, AC Supply find the inductance of the coil.
7. Define resonance and write the formula for the resonant frequency for RLC series circuit.
8. Why a parallel resonant circuit is called a rejecter circuit.
9. List the advantages of poly phase system over single phase system.
10. State the relation between line voltage and phase voltage, line current and phase current in delta connected network.

PART-B                                                5 X 10=50
Instructions: 1) Answer any five questions.
2) Each answer carries ten marks.

1. Two batteries E1 and E2 have emf’s 6 volts and 2volts respectively and external resistances of 2 ohms and 3 ohm respectively are connected in parallel across 5 ohms resistor. Calculate (a) the current in each of the battery (b) the potential difference across 5ohms resistor.
2. Derive the formula for delta to star transformation.
3. State and explain about thevenens theorem.
4. (a) Explain about phase and phase difference.

(b) A sine wave has a peak valve of 50 volts Determine

(i) RMS value (ii) Average value (iii)    form factor.

1. A resistance of 12 ohms, an inductance of 0.15 H and a capacitance of 100 micro farad are connected in series across a 100V, 50HZ, AC supply.

Calculate, (a) Impedance (b) current (c) power factor (d) power consumed.

1. Draw and explain the graphical representation of series resonance and indicate the following in the graph.

(a) Resonant frequency (b) net reactance (c) impedance (d) current.

1. (a) Define Q factor of a parallel resonant circuit.

(b) A coil of 20 ohms resistance and an inductance of 0.2H is connected in parallel with a   condenser of 100 micro farad capacitance. Calculate the frequency at which the circuit will act as a non inductance resistance of “R”ohms.also find the value of “R”.

1. Derive the formula for measurement of 3 phase power and power factor by using two watt meter method (balanced load).