Class
2nd YEAR Federal Board 2009
Paper:Physic (Objective Type) Time
Allowed: Max.Marks:
Note:Use this paper
to write the answers to the objective questions.No marks will be awarded
for cutting,over-writing
or using a pencil.This paper must be tagged with the answer-book.
1. Insert correct option.
(1) Viewed from above, the current in
a solenoid is anti-clockwise. What magnetic pole would the top end
of the solenoid be ?
(a) North pole
(b) May be North
or South
(c)South pole
(d) Insufficient
data
(2) If the distance between two charged
bodies is halved, what will the force between them become
?
(a) Double (b)
Four times
(c) Half (d)
One half
(3) The ratio of collector current to
the base current is nearly equal and is known as.
(a) Reverse
bias current (b)
Forward bias current
(c) Emitter
current (d)
Current gain
(4) 1 x 10 electrons pass through
a wire in 1 us .The current through the wire will be:
(a) 1.6x10-6
A (b)
3.6x10-6 A
(c) 2.6x10-6
A (d)
4.6x10-6 A
(5) What is the barrier potential of
silicon diode at room temperature ?
(a) O.3V (b)
O.7V
(c) 1V (d)
2mV
(6) Which of the following bands may
be either completely filled or partially filed by electrons but
can never
be empty ?
(a) Conduction
band (b)
Forbidden band
(c) Valance
band (d)
None of these
(7) By increasing the frequency of an
alternating current the value of inductive reactance.
(a) Increases
(b)
Does not change
(c) Decreases
(d)
None
(8) What is the % elongation when one
m long copper wire is stretched by 20cm due to a stress?
(a) 10 (b)
30
(c) 20 (d)
0.2
(9) What will be the output value of
an OR operation gate when both the switches.
(a) o (b)
Both a and 1
(c) 1 (d)
None of these
(10) What should be done to increase the sensitivity
of a Galvanometer ?
(a) Increase
the area of its coil (b)
Increase the area of its coil
(c) Place its
coil in a stronger field (d)
All of these
(11) A dynamo converts ?
(a) Mechanical
energy into electrical energy
(b) Electrical
energy into mechanical energy
(c) Magnetic
energy into mechanical energy
(d) Magnetic
energy into electrical energy
(12) What are the minority charge carries in an Ntype
substance ?
(a) Protons
(b)
Holes
(c) Positron
(d)
Electrons
(13) Which of the following cannot be accelerated
by an electric or magnetic field ?
(a) Electrons
(b)
Neutrons
(c) Positron
(d)
Alpha particles
(14) What does larger capacitance in AC circuit results
at the same frequency?
(a) More reactance
(b)
The same reactance
(c) Less reactance
(d)
Less reactance if voltage decreases
(15) What effect do two parallel wires carrying currents
in the opposite directions have on each other ?
(a) Repel (b)
Attract
(c) Have no
effect (d)
they cancel out their individual magnetic fields
(16) The amount of energy needed to remove electron
from the matal surface depends upon:
(a) Work (b)
Power
(c) Work function
(d) Power
function
(17) Electron in hydrogen atom jumps from any higher
orbit to 1st orbit. What is the set of lines emitted called
?
(a) Lyman series
(b)
Pffund series
(c) Paschen
series (d)
Bracket series
2. Attempt any FOURTEEN
parts.
(1) Two conducting spheres having
charges 3Q and 5Q attract each other with a force of 10 N. They
are
then touched with each other and then separated to the same distance
again. Calculate the
magnitude
and nature of force now.
(2) A conducting wire of resistance
''R'' is cut into three equal parts and then these three parts are
joined
in parallel. Calculate the equivalent resistance.
(3) At what speed of an observer
the length of an object will appear as 70% of its proper length
?
(4) What happens to light intessity
of lamps in a series circuit when more lamps are added in the circuit?
(5) Discuss the situation when.
(a) Electric
intensity at a point is zero but electric potential is not zero.
(b) Electric
potential at a point is zero but electric intensity is not zero.
(6) A balloon is negatively charged
by rubbing and then set free. It first clings to a wall but eventually
falls
down. Why?
(7) When we hold a live wire standing
barefoot we get an electric shock while wearing plastic or rubber
shoes
we don't. Explain the reason.
(8) In a hydrogen atom there are
two attractions between electron and proton.Name them.Also find
their
magnitudes if the radius of hydrogen atom is 0.053nm.
(9) Write down three difference
between Coulomb's electrostatic force and gravitational force.
(10) What will be the instantaneous value of
alternating voltage at time ''T/6'' where ''T'' is the time period
of the alternating voltage ?
(11) What factors make a fusion reaction
difficult to achieve ?
(12) How can radioactivity help in the
treatment cf cancer ?
(13) The decay constant for Sr is 1.99
x 10- S- calculate its half life.
(14) A capacitor is connected across
a battery.
(a) Why does each plate receive charge of exactly the same magnitude
?
(b) Is this true even is the plates are of different sizes?
(c) Will there be any current flowing through the circuit ?
(15) Find the equivalent resistance for
the combination show in the figure (Between A and B). Resistance
of each resistor is ''R''.
(16) Find the equivalent capacitance
of the circuit if the capacitance of each capacitor is ''C''.
(17) A series circuit of three identical
lamps is connected to a battery as shown in figure. When switch
''S''
is closed what effect will it have on the following:-
(a) Brightness of A and B,
(b) Brightness of lamp''C'',
(c) Current in the circuit.
(18) The resistance of a conductor decreases
with the increase in cross sectional area of the conductor. Why?
(19) Why do we choose a potentiometer
to measure potential difference accurately, rather than a voltmeter?
Attempt any TWO questions.
3.a) What is mutual induction?
Explain how induced emf is produced in the secondary coil. What
factors does
mutual induction depend upon?
b) Name the unit
of mutual induction and define it.
c) An emf of
5.6V is induced ina coil while the current ina nearby coil is decreased
from 100A to 20A in
0.02s. What is the mutual inductance of the two coils ? If the secondary
coil has 200 turns,find
the change
in the flux during this interval.
4.a) What is compton effect?
Prove that the wavelength of the photon increases after collision
with the electron.
b) A 50 keV photon
is Compton scattered by quasi free electron.If the scattered photon
comes off at 45
, What is its wavelength?
c) Explain why
bright light ejects more electrons from a metal surface than dimmer
light of the same colour
?
5.a) State the basic postulates
of Bohr's atomic model of the hydrogen atom. Also derive expressions
for radii
of quantized orbit of electron.
b) What is ment
by half life of a radioactive element? How can it be determined
from the decay constant
of radioactive element?
c) Comput the
shortest wave length radiation in the Balmer series. What value
of ''n'' must be used? And
why? |
