Download 1 - Moodle Ecolint

1.
A positively charged rod is placed near to the cap of an uncharged gold leaf electroscope. Which
one of the following diagrams correctly shows the distribution of charges on the electroscope as
well as the deflection of the gold leaf?
A.
B.
+ +
+ +
+
+ +
+ +
+
–––––
+
+
+
+
+
+
+
+
+
+
C.
D.
+ +
+ +
+
–––––
+ +
+ +
+
–––––
+
+
+
2.
3.
4.
+
+
Which one of the field patterns below could be produced by two point charges?
A.
B.
C.
D.
A plastic rod is rubbed with a cloth. At the end of the process, the rod is found to be positively charged
and the cloth is found to be uncharged. This involves the movement of
A.
positive charge from the cloth to the rod.
B.
positive charge from earth to the cloth.
C.
negative charge from the rod to earth. D.
negative charge from earth to the cloth.
The diagram below shows lines of electric equipotential. The change in potential on moving from one line
to the next is always the same. At which point does the electric field strength have its greatest magnitude ?
A
B
C
D
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5.
Two positive point charges P and Q are held a certain distance apart.
X
P
Q
Y
+
Z
+
At which point(s) could the electric field strength, due to the charges, be zero?
A.
6.
X only
B.
Y only
C.
Z only
D.
X and Z only
Two isolated spheres X and Y of unknown materials are touching one another as shown below.
sphere X,
earthed
sphere Y,
negatively charged
Sphere Y is negatively charged and sphere X is earthed. The earth connection is removed from sphere X
and then the spheres are separated as shown below.
sphere Y,
negatively charged
sphere X,
positively charged
Sphere X is found to be positively charged and sphere Y remains negatively charged.
Which of the following describes the nature of the materials from which the spheres are made?
7.
Sphere X
Sphere Y
A.
Insulator
Insulator
B.
Insulator
Conductor
C.
Conductor
Insulator
D.
Conductor
Conductor
This question is about electric charge at rest.
(a)
Define electric field strength at a point in an electric field.
(2)
Four point charges of equal magnitude, are held at the corners of a square as shown below.
2a
+Q
+Q
2a
P
–Q
–Q
2
The length of each side of the square is 2a and the sign of the charges is as shown. The point P is at the
centre of the square.
(b)
(i)
Deduce that the magnitude of the electric field strength at point P due to one of the
kQ
point charges is equal to
.
2a 2
(2)
(ii)
On the diagram above, draw an arrow to represent the direction of the resultant
electric field at point P.
(1)
(iii)
Determine, in terms of Q, a and k, the magnitude of the electric field strength at
point P.
(3)
(Total 8 marks)
8.
This question is about the electric field due to a charged sphere and the motion of electrons in that field.
The diagram below shows an isolated, metal sphere in a vacuum that carries a negative electric charge of
9.0 nC.
–
(a)
On the diagram draw arrows to represent the electric field pattern due to the charged sphere.
(3)
(b)
The electric field strength at the surface of the sphere and at points outside the sphere can
be determined by assuming that the sphere acts as though a point charge of magnitude
9.0 nC is situated at its centre. The radius of the sphere is 4.5 × 10–2 m. Deduce that the
magnitude of the field strength at the surface of the sphere is 4.0 × 104 Vm–1.
(1)
An electron is initially at rest on the surface of the sphere.
(c)
(i)
Describe the path followed by the electron as it leaves the surface of the sphere.
(1)
(ii)
Calculate the initial acceleration of the electron.
(3)
(iii)
State and explain whether the acceleration of the electron remains constant,
increases or decreases as it moves away from the sphere.
(2)
(iv)
6
–1
At a certain point P, the speed of the electron is 6.0 × 10 ms . Determine the
potential difference between the point P and the surface of the sphere.
(3)
(Total 13 marks)
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