Which of the following is a chemical change?
a. Dry ice subliming
b. Limestone being crushed to powder
c. Paper being shredded
d. Sulfur burning
d
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Transformers: The primary coil of an ideal transformer has 100 turns and its secondary coil has 400 turns. If the ac current in the secondary coil is 2 A, what is the current in its primary coil?
A. 2 A B. 8 A C. 1/2 A D. 1/4 A E. 4 A
Tarzan swings back and forth on a long vine. His friend Jane notices in amazement that he makes 30 complete swings in 2.4 minutes
(a) What is the frequency (in hertz) of Tarzan's swing? (b) How long is the vine he is using?
Two identical bar magnets are placed rigidly and anti-parallel to each other as shown. At what locations, if any, is the net magnetic field close to zero?
A thermodynamic engine absorbs 64 kcal of energy each cycle and exhausts 42 kcal
(a) What is the efficiency of this engine? (b) How much work does this engine do per cycle?