CIRCUITS II PROBLEM SETS (SERIES CIRCUIT)

1. An impedance coil is connected in series with a fixed resistor, and a 120 – V 25 cycle source is then impressed across the combination. If the voltage drops across the coil and resistor are 70 and 80 volts, respectively, when the current is 1.4 A, find the resistance of the coil. Ans. 13.84 Ω
2. A circuit consisting of a non –inductive resistance in series with a condenser is connected in series with a non – inductive resistance of 2 ohm across 220 volts, 25 – Hz mains. What is the capacitance when the entire circuit takes 300 W at a power factor of 0.2? Ans. 201 micro -Farad
3. A non – inductive resistance is in series with a condenser takes 7A and absorbs 300 W when connected across a 110 – V, 25 Hz mains. What non – inductive resistance must be connected in series with the circuit in order that it may take the same current from a 110 – V, 60 Hz supply? Ans. 8.38Ω
4. Find the value of impedance which absorbs a complex power of 5000∠45deg volt – amperes when the rms current through it is 12.5 A. Ans. 22.62 + j22.62 Ω
5. The resistance R and L of a coil are to be determined experimentally. The available equipment is a voltmeter and an 8 – ohm resistor. The 8 – ohm resistor is connected in series with the coil and the combination across a 120 V, 60 Hz source. If the voltmeter reads 32 V across the resistor, and 104 V across the coil, Find L. Ans. 63. 66mH
6. What is the inductance of the coil if it draws 0.55 A from a 110 – V, 60 Hz power line and 0.2 A from a 20 V battery? Ans. 0.459 H
7. A 5 micro-F capacitor is connected in series with a variable inductor to a 20 – V, 796 cycle source. For what value of inductance will the current be 2A leading? Ans. 6mH
8. An impedance coil is connected in series with a condenser across 220 – volt, 60 Hz source. The circuit absorbs 800 W at a power factor of 0.4 lagging and is so adjusted that the voltage across the condenser is 350 V. What is the voltage across the impedance coil? Ans. 558. 6 V
9. A coil draws 10 A when connected across a 100 V source. When a 10 – ohm resistor is connected in series with the coil, the current is reduced to 6 A. Determine the resistance of the coil. Ans. 3.89Ω
10. Find the current that will flow in a series circuit containing a 5 kΩ resistor, a 470 pF capacitor, a 150mH inductor, and a 0.001 micro-Farad capacitor if the exciting voltage is 65 V at 25Khz. Ans. 10.5 mA