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YEAR 12 PHYSICS TERM 1 REVISION
ELECTROSTATICS. SHEET 1 2011
Q 1. Describe what is meant (with diagrams where necessary) by the following terms :
induction, conduction and electrostatically neutral.
Q 2. Calculate the force of attraction between an electron and an alpha particle which are
10cm apart. (an -particle is a Helium nucleus)
Q 3. Calculate the speed at which an electron would be travelling just before hitting the
positive terminal of a 24V battery.
Q 4. Calculate the work required to move a proton from the negative terminal to the
positive terminal of a 12V battery. Convert this answer to electron Volts.
Q 5. Calculate the size of the electric field between the plates of a 24V battery which are
10cm apart.
Q 6. A charge of +7C is placed at 20cm on the x-axis and a charge of -12C is placed
at 90cm on the x-axis. Calculate the size and direction of the electric field at
(a.) x = 70cm., (b.) x = 5cm, (c.) x = 1m.
Q 7. Sketch electric field lines for the following cases :

(a.)

(b.)
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Q 8. Calculate the resistivity of a piece of copper wire which has a length of 30cm and a
diameter of 0.5mm if the measured resistance is 82m.
Q 9. (a.) Calculate the total resistance in the following circuit and find the readings on each
of the meters.
12V
V1
A1
20
40
V2
100
150
A2
(b.) Work out the number of electrons passing through each of the ammeters per second(i.e. t = 1s.
Q 10. Calculate the absolute potential at A.
-5C
+7C
0.4m
0.45m
A
0.38m
+2C
Q 11. The following data was recorded for an experiment where a ball with an unknown charge is moved
to various distances from a +3C charge. The unknown charge is attached to a spring balance and
the force required to keep the ball at equilibrium is recorded.
Distance d (cm)
Force F (N)
2
270
4
65
6
28
8
18
10
11
12
7
(a.) What sign must the unknown charge be. Please explain.
(b.) Draw a graph of the raw data and determine the general relationship between F and d.
(c.) Using trial products determine the relationship between F and d.
(d.) From one of your graphs determine the size of the unknown charge.(k = 9  109)
Q 12. Three resistors are placed in series (the current through each of them must be the same).
The following graph shows the Ohmic properties of the 3 resistors.
Voltage(V)
RA
RB
10
6
RC
2
0
1
2
3
4
5
6
7
8
9
Current (A)
Q 12. Cont…
(a.) If a current of 5A flows through resistor A what would be the potential difference across the resistor?
(b.) What would be the current flowing through resistors B and C and therefore what potential difference
would be across each of them?
(c.) What must be the voltage of the power supply?
(d.) Calculate the slope of each line.
(e.) What does the slope of this graph represent?
Q 13. A small ball of mass 0.5g and a charge of - 6C is suspended in mid air by an electric field of
unknown strength.
Calculate the size and direction of the electric field.
Q 14. Two balls of identical mass(m = 2g) and charge are brought near each other. They are 12cm apart
when equilibrium is reached. One ball is fixed and the other is attached to a horizontal spring which
is compressed by 4cm. (spring constant k = 20 Nm-1) Find the size of the charge.
fixed
compressed spring
Q 15. An electron enters an electric field at an angle of 60 0 upwards to the horizontal. The field is vertical
and pointing downwards. The electron is travelling at 4  107 ms-1.
The electric field strength is 2  104 NC-1. Calculate the velocity of the electron after 8ns.
ve
E
600