## Sunday, 9 July 2017

### CBSE CLASS 11 PHYSICS UNITS AND MEASUREMENT WORKSHEET

WORKSHEET#1 UNITS AND MESUREMENT
1. If the unit of force is 100N, unit of length is 10m and unit of time is 100s. What is the unit of Mass
in this system of units? 105kg.
2. Using dimensions convert (a) 1 newton into dynes (b) 1 erg into joules.
3. The magnitude of force experienced by an object moving with speed v is given by F = kv2. Find
Dimensions of k.
4. Give limitations of dimensional analysis.
5. For Determination of g using simple pendulum, measurements of length and time period are
required. Error in the measurement of which quantity will have a larger effect on the value of g           thus obtained. What is done to minimise error?
6. Describe the Parallax Method for the determination of the distance of a nearby star from the earth.
7. Define the following units :(i) Lightyear (ii) Parsec(iii) Astronomical unit (Au)
8. Distinguish between the terms precision and accuracy of a measurement.
9. Explain
(i) absolute error (ii) mean absolute error(iii) relative error (iv) percentage error
(v) random error
10. Determine the number of light years in one metre. 1.057 × 10-16 Iy
11. The sides of a rectangle are (10..5 ± 0.2) cm and (5.2 ± 0.1) cm. Calculate  its perimeter with error
limits. (31.4 ± 0.6) cm.
12. The mass of a box measured by a grocer’s balance is 2.3 kg. Two gold
pieces 20.15 g and 20.17 g are added to the box.
(i) What is the total mass of the box? 2.3 kg
(ii) The difference in masses of the pieces to correct significant figures. 0.02 g
13. 5.74 g of a substance occupies 1.2 cm3. Express its density to correct significant figures. 4.8 g/cm3.
14. If displacement of a body s = (200 ± 5) m and time taken by it t = (20 +0.2) s, then
find the percentage error in the calculation of velocity. 3.5%
15. If the error in the measurement of mass of a body be 3% and in the measurement of velocity be
2%.What will be the maximum possible error in the calculation of kinetic energy. 7%
16. The length of a rod as measured in an experiment was found to be 2.48m, 2.46m, 2.49m, 2.50m and 2.48m. Find the average length, absolute error and percentage error. Express the result with error
limit. (2.48 ± 0.01)m (2.48m ± 0.40%)
17. A physical quantity is measured as Q = (2.1 ± 0.5) units. Calculate thepercentage error in (1) Q2   (2) 2Q. 48% and 24%
18. When the planet Jupiter is at a distance of 824.7 million km from the earth, its angular diameter is
measured to be 35.72¢¢ of arc. Calculate diameter  of Jupiter. 1.4287 × 105 km
19. A laser light beamed at the moon takes 2.56s and to return after reflection at the moon.s surface.
What will be the radius of lunar orbit. 3.84 × 108 m.
20. Convert
(i) 3 m/s.-2 to km/ h-.2            3.9 × 104 km h-.2
(ii) G = 6.67 × 10.-11 N m2 kg-2 to cm3 g-1 s-2 6.67 × 10-8 g-1 cm3 s-2.
21. A calorie is a unit of heat or energy and it equals 4.2 J where 1J = 1 kg  m2s-2. Suppose we employ a
system of units in which unit of mass is a kg,  unit of length is b m, unit of time gs. What will be
magnitude of calorie in terms of this  new system. n2 = 4.2 a-1 b-2 g2

22. The escape velocity v of a body depends on.
(i) the acceleration due to gravity g of the planet,
(ii) the radius R of the planet. Establish dimensionally the relation for the escape
velocity

23. The frequency of vibration of a string depends of on, (i) tension in the string (ii) mass
per unit length of string, (iii) vibrating length of the string. Establish dimensionally the
relation for frequency.

24. One mole of an ideal gas at STP occupies 22.4 L. What is the ratio of
molar volume to atomic volume of a mole of hydrogen? Why is the ratio
so large. Take radius of hydrogen molecule to be 1ºA.  104 This ratio is large    because actual size of gas molecule is negligible incomparison to the inter molecular separation.

25. Derive an expression for the centripetal force F acting on a particle of
mass m moving with velocity v in a circle of radius r.

26. The error in the measurement of radius of a sphere is 2%. What would be
the error in :
(a) Volume of sphere

(b) Surface area of sphere.

## Sunday, 2 July 2017

### class 12 cbsevWORKSHEET#2 ELECTRIC POTENTIAL AND CAPACITANCE

WORKSHEET#2 ELECTRIC POTENTIAL AND CAPACITANCE

2MARK
1)Draw E and V versus r on the same graph for a point charge.
2) Find position around dipole at which electric potential due to dipole is zero
but has non zero electric field intensity.
3) The electric potential V at any point in space is given V = 20x3 volt, where x is in
meter. Calculate the electric intensity at point P (1, 0, 2).
Ans. 60 NC.1
4)  Justify why two equipotential surfaces cannot intersect.
5Find equivalent capacitance between A and B in the combination given below : each capacitor is
of  2 µF. Ans. 6/7 µF
6) For an isolated parallel plate capacitor of capacitance C and potential difference V, what will be change in (i) charge on the plates (ii) potential difference across the  plates  (iii) electric field between the plates (iv)energy stored in the  capacitor, when the   distance between the plates is increased ?
Ans. (i) No change (ii) increases (iii) No change (iv) increases.
7) A RAM (Random access Memory) chip a storage capacitor has a capacity of 55pF. If the    capacitor is charged to 5.3V, how may excess electrons areon its negative plate ? Ans. 1.8 × 109
8) What is electric field between the plates with the separation of 2 cm and (i)with air (ii) dielectric medium of dielectricconstant K. Electric potentialof each plate is marked in the following figure.

9) The figure shows the Q (charge) versus V (potential) graph for a combination of two capacitors. identify the graph representing the parallel combination.

10) Calculate the work done in taking a charge of 1µC in a uniform electric field of 10 N/C from B to C given AB = 5 cm along  the field and AC = 10cm  perpendicular to electric field.
11) Two charges -q and + q are located at points A (0, 0, -a) and B (0, 0, + a) respectively. How much work is done in moving a test charge from pointP (7, 0, 0) to Q (-3, 0, 0) ? (zero)
12) The potential at a point A is -500 V and that at another point B is + 500 V. What is the work done by external agent to take 2 units (S.I.) of negative charge from B to A.
13)  How does the Potential energy of (i) mutual interaction (ii) net electrostatic P.E. of two charges change when they are placed in an external electric field.
14) With the help of an example, show that Farad is a very large unit of capacitance.
15)  What is meant by dielectric polarisation ? Why does the electric field inside  a dielectric decreases when it in placed in an external field ?
16) In charging a capacitor of capacitance C by a source of emf V, energy supplied by the sources QV and the energy stored in the capacitor is ½QV. Justify the difference.
3 Mark
1) Define electrostatic potential and its unit. Obtain expression for electrostatic potential at a point P in the field due to a point charge.
2)  Calculate the electrostatic potential energy for a system of three point charges placed at the corners of an equilateral triangle of side a
3)  What is polarization of charge ? With the help of a diagram show why the electric field between the plates of capacitor reduces on introducing a dielectric slab. Define dielectric constant on the basis of these fields.
4) Three capacitors are connected ®rst in series and then in parallel. Find the equivalent capacitance for each type of combination.
5) A charge Q is distributed over two concentric hollow sphere of radii r and R (R > r), such that their surface density of charges are equal. Find Potential at the common centre.
6) Derive an expression for the energy density of a parallel plate capacitor.
7) You are given an air filled parallel plate capacitor. Two slabs of dielectric constants K1 and K2 having been filled in between the two plates of the capacitor as shown in Fig. What will be the capacitance of the capacitor of initial area was A distance between plates d ?
8) A conducting slab of thickness .t. is introduced between the plates of a parallel plate capacitor, separated by a distance d (t < d). Derive anexpression for the capacitance of the capacitor. What will be its capacitance when t = d ?
9) If a dielectric slab is introduced between the plates of a parallel plate capacitor after the battery is disconnected, then  how do the followingquantities change.(i) Charge(ii) Potential(iii) Capacitance (iv) Energy.
10) What is an equipotential surface ? Write three properties Sketch equipotential surfaces of(i) Isolated point charge(ii  Uniform electric field(iii) Dipole
11) If charge Q is given to a parallel plate capacitor and E is the electric field between the plates of the capacitor the force  on each plate is 1/2 QE and if charge Q is placed between the plates experiences a force equal to QE. Give reason to explain the above.
12) Two metal spheres A and B of radius r and 2r whose centres are separated by a distance of 6r are given charge Q, are at potential V1 and V2. Find the ratio of V1/V2. These spheres are connected to each other with the help of wire connecting wire keeping the separation unchanged, with its the amount of charge that will flow through the?

13) Define potential gradient. How can potential gradient of a potentiometers be determined experimentally. In the graph shown here, a plot of potential drop versus length of the potentiometer is made for two potentiometers.B ?
Which is more sensitive A orB?