Work and power of alternating current
Answers are for parents and teachers.
1
U = 120 V, I = 5 A, cosφ = 0.8. What is P in W?
480
2
P = 440 W, U = 220 V, cosφ = 1. What is the current in A?
2
3
For the same P and U with cosφ = 0.5, what is the current in A?
4
4
R = 40 Ω and Z = 50 Ω. What is cosφ?
0.8
5
Why is no heat released in reactive elements although a current flows?
Energy is alternately stored in the field and returned to the source; the mean power consumed is zero.