PHYSICS 2210 RMU Paper 1 and 2

PHYSICS 2210 RMU Paper – 2 for performance enhancement
(Optional)
The
solutions/answers are due in class on Tuesday, 09 December 2014.
[Essay question 7: 20
points; questions 8 to 12: 10 points each]
7.
Suppose the refractive index of air were 1.5, of water 1.3 and of glass
1.0.How would these
affect everyday phenomena? Consider the science ofOptics including but not limited to lenses,
refraction, interference effects etc. in framing your answer in the form of a
two-page essay, in double-spaced typing. The essay would be graded depending upon yourthoroughness, creativity, accuracy and concern
for the laws of Physics.Feel free also to embark on your own studies to consider areas which you
may not have covered in your courses.
You may exceed the two-page limitifyou
have more to offer.
8.
As shown below, a network of resistorsR1andR2extends to infinitytoward the right. Prove that the total
resistance RT of the infinite networkis given by:
RT’RI± Ri2 +2 R2
le

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9.) A parallel plate capacitor has the space
between the plates filled with two
slabs of dielectric, one with a constant Kl and the other with a
constantK2.Each slab has a
.gif”>.gif”>.gif”>thickness (d/2) where ‘d’ is the plate separation. Show that the capacitanceof the capacitor is
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K2 )
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d ( + K2 )

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10.
.gif”>A piece of uniform wire is made up into two squares with a common sideof length 4 cm. A current enters the system at
one of the corners A and leaves at the diagonally opposite corner F. Show that
the current in thecommon side
is one-fifth of the entering current (i.e, show that14 =11/5).
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11.
Two identical
spheres with mass m are hung from silk
threads as shown on the right. Eachsphere
has the same charge, so that
q1 = q2 = q. The
radius of each sphere is
very small compared to the
distance between the spheres, so that they
may be treated aspoint charges. Show that if 0 is small, the equilibrium distance between the spheres isgiven
by
d (q2
L / 27( Eo m g )1/3Note that
sin H = tan 0 for small H.

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12.
.gif”>Each of two perpendicular wires lying in the
plane of the papercarries the
same currentI.What is the
direction of the net magneticfield at (a) point A and (b) point B? Is the magnitude of the net
magnetic field at point A greater than, less than or equal to themagnitude of the net magnetic field at point
B?
If the current in each of the wires is I =
5.6 A, find the magnitudes ofthe net fields at points A and B. Verify that your answers are
consistent with your answers to the questions in the previousparagraph.
0

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previou
PHYSICS 2210 RMU Paper – 1 for performance enhancement
(Optional)
The
solutions/answers are due in class on Tuesday, 09 December 2014.
[Essay question 1:20 points; questions 2 to 6: 10 points each]
1.) Suppose the speed of light were 50 miles per
hour (approximately 22 m/s).
Write a two-page essay, in double-spaced typing,discussing itsramifications on your everyday life. The
essay would be gradeddepending upon your thoroughness, creativity, accuracy and concern forthe laws of Physics. Feel free also to embark
on your own studies toconsider areas which you may not have covered in your courses.
You may exceed
the two-page limit if
you have more to offer.
2.) Two charges of equal magnitude Q are held a
distancedapart. Consider
only points on the line passing through both
charges.
(a)
(i) If the two charges have thesamesign, find the location of all
points, if
any,where the electric potential is zero. Is the electric fieldalso zero at these points?
(ii) If the two charges have thesamesign, find the location of allpoints, if
any,where the electric field is zero. Is the electric potential also
zero at these points?
(b)Repeat part(a)above for two charges havingoppositesigns.
Can you conclude that the electric field is always zero at any point
wherethe electric
potential is zero?
Likewise, Is the electric potential always zero at any point where theelectric field is zero?
Please explain
your answers clearly in all cases. Diagrams could be veryhelpful.

3.) Twelve resistors, each of
resistance R ohms, form
a cube, as shown in the figure. Find, in
terms of R,the following:
(a)RAB, the equivalent resistance
of an edge.
(b)Roc,the equivalent resistance of a
face diagonal.
(c)RAG, the
equivalent resistance of a body diagonal.

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4.
Four very long current carrying wires in the sameplane intersect to form a square
40 cm on eachside, as
shown at right. Find the magnitude anddirection of the current ‘I’ so that the
magneticfield at the
centre of the square is zero.
Assume that there is no shorting due to any overlapping wires.

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5.
.gif”>.gif”>For the circuit shown below, find the current
through each resistor.
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6.
.gif”>.gif”>.gif”>.gif”>What is the magnitude of the currentiin the circuit
below where each ofthe resistances is 4 Q and all each of the batteries has an emf of 10
Volts?DO NOT TRY TO
SOLVE THIS PROBLEM THROUGH MULTIPLEEQUATIONS INVOLVING KIRCHHOFF’S LAWS. Try to
find anappropriate path and you can answer this question with only a fewseconds of
mental calculation.
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