Alternating Current

A. Twice
B. One half
C. Four times
D. None

A. Sound waves
B. Electromagnetic waves
C. Radio waves
D. Modulated waves

A. Electric and magnetic fields moving parallel to each other
B. Magnetic field moving with velocity of light in space
C. Electric field moving with velocity of light
D. Electric and magnetic fields moving perpendicular to each other

A. λ-rays
B. Positive rays
C. Cathode rays
D. More than sound waves

A. fluctuates off and on
B. varies in magnitude alone
C. changes its direction again and again
D. changes its magnitude harmonically and reverses its direction of flow after regularly recurring intervals