R.M.S. VALUES OF CURRENT AND E.M.F. 35 



value is 100 volts, and frequency 100 cycles, per second, is applied between its 

 terminals ? 



Answer. 0-126 ampere. 



2. What is the impedance of the circuit in Question 1 ? 

 Answer. 795'2 ohms. 



3. What is the difference in phase between E.M.F. and current in Question 1 ? 

 Draw curves respecting them. 



Answer. 82 50'. 



4. What is the self-induction of a coil through which, when 100 R.M.S. 

 volts is applied between its terminals, a current of 5 amperes passes, the 

 frequency being 80 periods per second, and the resistance of the coil being 

 0-5 ohm ? 



Answer. 0-0386 henry, nearly. 



5. The maximum value of an alternating current is 100 amperes : what is 

 its average value over half a period from zero to zero? 



200 

 Answer. amperes. 



6. The R.M.S. value of an alternating E.M.F. is 100 volts: what is its 

 maximum value ? 



Answer. 141 '4 volts. 



7. A coil having a self-induction of - 05 henry allows a current of 3 R.M.S. 

 amperes to pass when the frequency is 100 : what is the P.D. between its 

 terminals, the resistance of the coil being neglected ? 



Answer. 94 25 volts. 



8. What is the P.D. in Question 7, if the resistance of the coil is 5 ohms ? 

 Answer. 95*4 volts. 



9. What is the frequency when a current of 1 ampere is sent through a coil 

 having a self-induction of 0-75 henry, a P.D. of 200 volts being applied between 

 its terminals, the resistance of the coil being negligible ? 



Answer. 42-44. 



10. What is the frequency in Question 9, if the resistance of the coil is 10 ohms ? 

 Answer. 42-4. 



11. A condenser of capacity 10 microfarads is connected between the 

 terminals of an alternator giving 1000 volts at a frequency of 50 periods per 

 second : what is the current ? 



Answer. TT amperes. 



12. If a resistance of 10 ohms is inserted in series with the condenser in 

 Question 11, what current will pass ? 



Answer. 314 amperes. 



13. If a self-induction of 0'05 henry is placed in series with a capacity of 

 1 microfarad, and a P.D. of 100 volts, at a frequency of 100 periods per second, 

 be applied between the extreme terminals, what is the current ? 



Answer. 0'0641 ampere. 



14. A circuit contains in series a resistance of 10 ohms, a self-induction of 

 0-5 henry, and a capacity of 0-5 microfarad : what is the current if the P.D. 

 between the terminals of the arrangement is 100 volts, and the frequency 80 

 periods per second ? 



Answer. 0-0268 ampere. 



