s AM) /7,'o/>-/./-;.u.s 473 



for what value of the capacitance will the current be a maximum? If the 

 lino voltage is 20 volts, what are the current, power, power-factor and the 

 various voltages? 



38. A rosi-tance of 10 ohms, a 50 m.f. condenser and an inductance of 

 ()(>.") henry are connected in parallel across 100-volt 60-cycle mains. What 

 current does each take and what is the total line current ? 



39. An inductance having negligible resistance and a condenser are 

 connected in parallel across 25-cycle mains. Each takes 2 amp. (a) How 

 much current does the line supply? (6) If the frequency is doubled, how 

 much current does the line supply? 



40. A non-inductive resistance and an impedance coil are connected in 

 series across 120-volt 60-cycle mains. The voltage across the resistance 

 is found to be 90 volts and that across the impedance 60 volts. If the 

 current is 5 amp., determine (a) the circuit power (6) the circuit power- 

 factor (c) the impedance power-factor (d) the inductance of the impedance 

 coil. 



41. To measure the power consumed by a US-volt single-phase induction 

 motor, it is connected in series with a non-inductive resistance across 220- 

 volt mains. When the motor takes 20 amp. the resistance is so adjusted 

 that the voltage across the motor terminals is 115 volts and that across 



Distance is 127 volts. What power is the motor taking and what is the 

 power-factor of the motor and of the system? 



42. A series alternating-current circuit consisting of a resistance, an 

 impedance coil and a condenser having negligible leakage takes 420 watts at 

 115 volts, 60 cycles and 5 amp. lagging current. The voltage across the 



volts and that across the capacitance is 90 volts. Find 



(a) the power consumed in the re<i<tanco. (l The power consumed in the 



impedance coil, (n The voltage across the impedance coil, (d) The capaci- 



of the condenser in m.f. (e) The inductance of the impedance coil 



in he: 



43. A series circuit consisting of a resistance of 10 ohms, an inductance 

 ' -i-tance negligible) and an unknown condenser all in series is con- 



'lt 60-cyele mains. When 10 amp. loading current 



flow in the circuit the combined voltago across the capacitance and induc- 

 tance is 250 volts. What i- the value of the unknown capacitai. 



44. A non-inductive re :id an im|>edance coil are connected in 

 parallel across 1 10- volt 60-cycle mains. When the impedance and resis- 

 tance each take 20 amp. the lino current La .TJ amp. What power 

 impedance taking? The circuit? What i* the power-factor of each? 



45. A non-inductive resistance, an impedance and a condenser 1> 

 negligible power loss are all connected in parallel across 110-volt 60 

 mains. The resistance takes 12 am p.. the . .uulenser 10 amp., the impedance 

 13 amp. and th. to these three. Find (o) the circuit 



t.-tor; (c) the power taken l.y the impedance; 

 (d) the impedun 



46. A certain load takes 2 kw. at . -i<) cycles and at a power-factor 



