MEETING 1, 2 AND 3 ACTIVITY TASK
1. Calculate the average voltage induced in a coil of 300 turns through which the flux changes
from 250,000 to 20,000 maxwells in 0.15 second.
2. A current wave has an equation i = 21.2 sin α. At what angle will the instantaneous values of
current be (a) 13.6 Amps? and (b) -19.9 Amps?
3. What are the frequencies of the following sinusoidal waves: (a) E = Em sin 314 t, and
(b) I = Im sin 251 t?
4. A 25-cycle sinusoidal Emf has a maximum value of 340 volts. Determine the instantaneous
value of Emf (a) 0.007 sec. after the wave passes through zero in a positive direction, and
(b) 0.01 sec. after the wave passes through zero in a negative direction.
5. Two equal voltages are out of phase with respect to each other by 90 electrical degrees. If their
geometric sum is 311 volts, calculate the rms value of each one.
6. The resultant value of two currents that are out of phase with each other by 60 electrical
degrees is 70 amperes. If one of them is 50 Amperes, what are the others?
7. The following information is given in connection with an AC source that delivers current to
three loads in parallel: IA = 20 amperes, IB = 12 amperes and lags behind IA by 30 electrical
degrees, IC = 32 amperes and leads IA by 60 electrical degrees. Using IA as the reference
phasor, determine the resultant current and the angle between it and IA.
8. Draw and find the phase difference between the waveforms E = 500 sin (ωt – 45º) V and
I = 150 sin (ωt + 210º) A.
9. An Emf given by E= 75 sin 120πt is applied to a circuit which offers a resistance of 25 Ω. Find
the rms and average values of the current in the circuit and also find its form factor.
10. Two electric units are connected across a source whose frequency is 60 cycle per second. If
the rms values of the voltage drops across the units are 100 and 125 volts and they are out of
phase by 90º, what is the equation of the voltage across the source?