Four equal negative point charges are located at the corners of a square, their positions in the xy-plane being (1,1), (?1,1), (?1,?1), (1,?1). The electric field on the x-axis at (1,0) points in the same direction as
A) i^
B) j^
C) -i^
D) -j^
Answer: C) -i^ (-x direction // to left)
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Two wires have a nearly equal electron number density. Assume that the electric field in each wire points directly along the wire, that electric fields in the two wires have the same magnitude, but that the conductivity in wire A is twice that in wire B. This means that the drift velocity in wire A is b times that in wire B, where b is
A. 4 B. 2 C. 1 D. 1/2 E. 1/4 F. Impossible to determine from the given information
A sprinter named Ben has challenged a beam of light to a race in the 100-meter dash. The race is held in a stadium full of spectators. At the start signal, a laser beam is turned on at the start line, pointed down the track
At the same instant, Ben bursts out of the starting blocks at 99% of the speed of light (0.99c). According to the spectators watching in the stands, what happens? (Assume they could somehow watch a slow-motion replay to see what occurred.) A) The light beam wins the race, but barely—it is going 1% of the speed of light faster than him. B) The light beam instantly finishes the race, before Ben even has a chance to start. C) The light beam wins the race by a large margin because it is going faster than him by the full speed of light. D) Ben beats the light beam to the finish line, becoming a hero.
Lift an object against the force of gravity if you want to judge its
A) mass. B) weight. C) both the same D) none of the above
The distance between adjacent orbits in a hydrogen atom
A) varies randomly with increasing values of n. B) decreases with increasing values of n. C) remains constant for all values of n. D) increases with increasing values of n.