Download Physics 12

Physics 12
Version 1
Name: ____________
Electric Fields and Potential Unit Test
Part A: Multiple Choice (2 marks each)
(1) What are the units of electric field strength?
a.
N/C
b. V/m
c. both a. and b.
d. neither a. nor b.
(2) What is the magnitude and direction of the electric field at point P?
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a. 2.4 x 10 N/C left
4
b. 3.0 x 10 N/C left
4
b. 2.4 x 10 N/C right
4
d. 3.0 x 10 N/C right
(3) The electric field 20 mm from an unknown charge has a magnitude of 1.0 x 10
N/C. The magnitude of the electric field 10 mm from the charge is:
5
a. 4.0 x 10 N/C
4
c. 5.0 x 10 N/C
5
5
b. 2.0 x 10 N/C
4
d. 2.5 x 10 N/C
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(4) A proton is accelerated from rest through a 1.0 x 10 volt potential difference. What
speed does the proton attain?
4
a. 1.4 x 10 m/s
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c. 1.9 x 10 m/s
7
b. 1.4 x 10 m/s
14
d. 1.9 x 10 m/s
(5) An electron accelerated in a vacuum through a potential difference of 'V' acquires a
speed of 'v'. What speed does it acquire if the potential difference is '4V'?
a. 16 v
b. 4 v
c. 2 v
d. v
2
(6) The potential difference between two parallel conducting plates is 8.7 x 10 V and
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their separation is 0.400 cm. Find the work necessary to move 3.2 x 10 C of positive
charge from the negative to the positive plate.
a. 0.0278 J
b. 0.0295 J
c. 6.95 J
d. 2.78 J
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(7) A proton with kinetic energy of 2.1 x 10
J is moving into a region of charged
parallel plates. The proton will be stopped momentarily in what region?
a. Region K
b. Region L
c. Region M
d. Region N
(8) An electron moves from the negative plate to the positive plate in the situation
shown below. It moves __________________ of the electric field and experiences a
______________ in potential energy.
a
c.
with the direction ; gain
against the direction ; gain
b. with the direction ; loss
d. against the direction ; loss
Part B: Written Questions
(1) The nucleus of a helium atom contains 2 protons. An electron orbits the nucleus
at a point 4.0 nm away. What is the magnitude and direction of the electric field at the
location of the electron? (3 marks)
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(2) An electron moving at 7.5 x 10 m/s enters an electric field between parallel plates
by passing through a small hole in one of the plates as shown.
a) What is the impact speed on the second plate? Ignore friction. (4 marks)
b) If the plates are moved closer together, and the electron is released through
again, will its impact speed be the same, greater, or less? ________ (1 mark)
c) Explain using principles of Physics (2 marks).
(3) A small 0.0021 kg plastic ball is suspended by a string in a uniform electric field as
shown. Calculate the charge on the ball (4 marks)
(4) A helium nucleus having twice the charge and four times the mass of a proton is
traveling with a high velocity when it enters a set of charged plates as shown.
What is the magnitude and direction of the acceleration of the nucleus? (4 marks)
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BONUS: The plates are 1.0 m long and the nucleus enters at 1.5 x 10 m/s. What is
the deflection of the helium nucleus just before it exits the plates? (1 mark)