On the average during good weather, the Earth has a positive surface charge. Which is the usual direction of the Earth's electric field at the Earth's surface?
a. down
b. up
c. some direction parallel to the Earth's surface
d. north.
[Ques. 2] A Ferris wheel, rotating initially at an angular speed of 0.500 rad/s, accelerates over a 7.00-s interval at a rate of 0.0500 rad/s2 . What angular displacement does the Ferris wheel undergo in this 7.00-s interval?
a. 4.48 rad
c. 4.73 rad
b. 2.50 rad
d. 0.500 rad
[Ques. 3] If the dielectric breakdown field in air is 3 106 V/m, what potential difference is involved with a 3 cm spark?
a. 1.0 108 V
c. 9 104 V
b. 9 106 V
d. 1.0 1010 V
[Ques. 4] A Ferris wheel, rotating initially at an angular speed of 0.16 rad/s, accelerates over a 7.0-s interval at a rate of 0.050 rad/s2 . What is its angular speed after this 7.0-s interval?
a. 0.46 rad/s
c. 0.51 rad/s
b. 0.85 rad/s
d. 1.2 rad/s
[Ques. 5] If a lightning bolt involves a discharge of 48 coulombs, about how many electrons are involved?
a. 3 1023
c. 0.3 1018
b. 3 1020
d. 0.3 108
[Ques. 6] A Ferris wheel starts at rest and builds up to a final angular speed of 0.70 rad/s while rotating through an angular displacement of 2.5 rad. What is its average angular acceleration?
a. 0.098 rad/s2
c. 1.8 rad/s2
b. 0.05 rad/s2
d. 0.60 rad/s2
[Ques. 7] Two parallel-plate capacitors have the same plate area, and the gap between the plates is filled with a dielectric with a dielectric constant equal to 6 . The gap in capacitor A is three times that in capacitor B. What is the ratio of the capacitance of A to B?
a. 1/3
c. 3
b. The ratio is not given.
d. 18
[Ques. 8] Starting from rest, a wheel undergoes constant angular acceleration for a period of time T. At which of the following times does the average angular acceleration equal the instantaneous angular acceleration?
a. 0.50 T
c. 0.71 T
b. 0.67 T
d. all of the above
[Ques. 9] Very large capacitors have been considered as a means for storing electrical energy. If we constructed a very large parallel-plate capacitor of plate area 10 m2 using paper (k = 3.7) of thickness 1.0 mm as a dielectric, how much electrical energy would it store at a plate voltage of 5000 V? (e0 = 8.85 10-12 C2/Nm2)
a. 4.1 J
c. 0.41 J
b. 8200 J
d. 82,000 J
[Ques. 10] Starting from rest, a wheel undergoes constant angular acceleration for a period of time T. At what time after the start of rotation does the wheel reach an angular speed equal to its average angular speed for this interval?
a. 0.25T
c. 0.67T
b. 0.50T
d. 0.71T
Quick Reply
