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Lectricity, Magnetism &Amp; Modern Physics Question Paper
Lectricity, Magnetism &Amp; Modern Physics
Course:Certificate In Pre-Tech Physics (Pre-Tech Physics)
Institution: Kabarak University question papers
Exam Year:2009
KABARAK
UNIVERSITY
EXAMINATIONS
2008/2009 ACADEMIC YEAR
FOR THE CERTIFICATE OF PRE- UNIVERSITY PHYSICS
COURSE CODE: PPHYS 011
COURSE TITLE: ELECTRICITY, MAGNETISM &
MODERN PHYSICS
STREAM:
SEMETER
ONE
DAY: WEDNESDAY
TIME:
9.00
–
11.00
A.M.
DATE: 18/03/2009
INSTRUCTIONS:
Answer QUESTION 1 and ANY OTHER TWO
You may need the following constants:
-
Electron charge e = -1.6 x 10-19 C.
-
Proton charge e = 1.6 x 10-19 C.
-
p = 3.14
-
eo = 8.85 x 10-12 F/m
-
µo = 4p x 10-7 Tm/A
-
Planck's
Constant h = 6.626 x 10-34 J.s
PLEASE TURN OVER
Page 1 of 4
Question 1 (30 marks)
(a)
Give
any
THREE
properties
of
charge
(3
mks)
(b)
State
how
electrostatic
charge
can
be
created.
(2
mks)
(c)
What
do
electric
field
lines
represent?
(2
mks)
(d)
Some resistors are colour coded; hence their values can be determined from the
colour bands on them.
(i)
Give the colour referencing for each value 0-9.
(5 mks)
(ii)
Determine the value of a resistor with the following colour coding:
1st band - brown
2nd
band
-
black
3rd
band
-
brown
4th
band
–
gold
(6 mks)
(e)
Explain why batteries are sometimes referred to as capacitors.
(2 mks)
(f)
Why is it preferred to use the word “POOR CONDUCTORS” instead of “BAD
CONDUCTORS” when referring to electrically insulating materials?
(2 mks)
(g)
Explain why a material like steel retains its magnetism when it is magnetised as
opposed
to
soft
iron.
(4
mks)
(h)
A magnetic field can create a force on an object. Give three conditions that must
apply for the object to feel a force, and the magnetic field to affect the object.
(3 mks)
(i)
Sketch a general radioactivity curve for any radioactive material.
(2 mks)
Question 2 (20 marks)
(a) State
the
Coulomb’s
law
of
charges.
(2
mks)
(b)
(i)
For the figure below, determine the force between the two point charges
given
q1= +12×10-9 C and q2= -18×10-9 C.
(2 mks)
(ii) Is
the
force
attractive
or
repulsive?
(1
mk)
(iii) Suppose q1 and q2 are connected by a conducting wire. Now what is the
force?
(5 mks)
(c) (i) Define
Capacitance
and
give
its
SI
units
(2
mks)
(ii)
If a capacitor has 3.5 µC of charge on it and an electric field of 2.0 kV/mm is
desired if they are separated by 5.0 mm of air, what must each plate's area be?
Page 2 of 4
(4 mks)
(d)
Two huts A and B were put up in a lightning prone area. The roof of Hut A
comprises of iron sheets which were long enough to touch the ground. Hut B was a
tent made up of canvas which is electrically insulating. Which hut is relatively safer to
be in when lighting strikes? Give a reason for your choice.
(4 mks)
Question 3 (20 marks)
(a) State
Kirchoff’s
current
and
voltage
laws
(4
mks)
(b)
Apply Kirchoff’s laws to find the current through R4 in the circuit below if V = 30 V,
R1 = 12 , R2 = 18 , R3 = 9 , and R4 = 6 .
(7
mks)
(c) (i) Draw
a
sketch
of
a
power
transformer
(3
mks)
(ii)
Explain why for long distances, power companies prefer to transmit electricity
at
high
voltages.
(in
kilovolts
range)
(2
mks)
(iii)
The input to a primary coil of a transformer is 120 V while the current in the
secondary coil is 0.10 A.
(I)
Find the voltage across this coil when 60.0 W of power are delivered to
the circuit attached to the secondary coil.
(2 mks)
(II)
If the primary coil has 20 turns, how many does the secondary coil
have?
(2 mk s)
Page 3 of 4
Question 4 (20 marks)
(a) Explain
the
term
radioactivity.
(2
mks)
(b)
Explain the following radioactive decay process giving an example of each.
(i)
a
lpha
(3 mks)
(ii)
b
eta
(3 mks)
(iii)
ga
mma
(3 mks)
(c)
(i)
Give the condition for photoelectric effect to occur in a material.
(2 mks)
(ii)
Red light of wavelength 670.0 nm produces photoelectrons from a certain
metal which requires a stopping potential of 0.5 V to stop. What is the work
function and threshold wavelength of the metal?
(7 mks)
Page 4 of 4
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