Bert says that a charged particle in a vacuum can travel in a helix only if a uniform electric field and a uniform magnetic field are both present and both parallel to the axis of the helix. Stuart says that only a magnetic field with a component parallel to the axis of the helix is needed. Which one, if either, is correct, and why?
a. Bert, because the charged particle's velocity can have a vertical component only if an electric field in the vertical direction is present.
b. Stuart, because a component of velocity in the vertical direction is not changed by a vertical component of a magnetic field.
c. Bert, because a component of velocity in the vertical direction is changed by a vertical component of a magnetic field.
d. Stuart, because an electric field in the vertical direction would cause the particle to come to a complete stop.
e. Neither, because particles cannot move in helical paths in the presence of magnetic and electric fields.
b
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A neutral metal ball is suspended by a string. A positively charged insulating rod is placed near the ball, which is observed to be attracted to the rod. This is because:
A. the ball becomes positively charged by induction B. the ball becomes negatively charged by induction C. the number of electrons in the ball is more than the number in the rod D. the string is not a perfect insulator E. there is a rearrangement of the electrons in the ball
The term observable universe refers to
A) that portion of the universe that we have so far photographed through telescopes. B) the portion of the universe that can be seen by the naked eye. C) the portion of the universe that is not hidden from view by, for example, being below the horizon. D) that portion of the universe that we can see in principle, given the current age of the universe.
Series/Parallel Circuits: Draw a circuit with two batteries, a resistor between them, and a capacitor in parallel with the resistor. The batteries are connected negative pole to positive pole.
A. 
B. 
C. 
D. 
A jumbo jet of mass 100,000 kg during takeoff experience a thrust for each of its four engines of 50,000 N, producing an acceleration of
A) 0.5 m/s2. B) 1 m/s2. C) 2 m/s2. D) 4 m/s2. E) none of the above