No magnetic force acts on a current carrying wire when it
A) carries a very small current.
B) is perpendicular to the magnetic field.
C) either or both of these
D) none of the above
Answer: D
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A dc motor is connected to a emf of 12.0 V. The resistance of its windings is 2.0 
At normal operating speed, the motor delivers 6.0 W of mechanical power. What current does it draw at normal operating speed?
A. 6.0 A B. 0.50 A C. 1.0 A D. 3.0 A
2.9×10^7 is the same as
a. 2.9 thousand. b. 29 thousand. c. 290 thousand. d. 2.9 million. e. 29 million.
Consider the two surfaces shown below. They are both immersed in a uniform vertical electric field, and have the same cross-sectional area on the horizontal plane. (The tile vectors shown are for a typical tile on each surface.) 
For which surface is the value of 
larger?
A. The flat surface. B. The curved surface. C. The value is the same nonzero number for both. D. The value is zero for both surfaces. E. One cannot compare the values from what is given.
A current I = 3 sin (400 t) amperes flows in a series RL circuit in which L = 1 mH and R = 100 ?. What is the average power loss?
A. 225 W B. 450 W C. 980 W D. 1.12 kW E. 900 W