Subject: Physics

ELECTROSTATICSELECTROSTATICSELECTROSTATICSELECTROSTATICS 1.Dielectric constant of water is 80.What is its permittivity?

2.A sphere S 1 of radius r 1 encloses a total charge Q .If there

in another concentric sphere s 2 of radius r 2 (r 2

there be no additional charges between S 1

and S 2, find the ratio of the electric flux through S 1 and S 2 .How will the electric

flux through sphere S 1 change, if a

medium of dielectric constant S is

introduced in the space inside S 2 in place of air.

3 Determine the magnitude of an electric field that will

balance the weight of an electron.

4.n small drops of same size are charged to V volts each.

They coalesce to form a bigger drop. Calculate potential of

bigger drop.

5. Calculate the Coulomb force between two α -

separated by a distance 3.2 x10 –15 m.

6.Two points electric charges of values q and 2 q are kept at

a distance d apart from each other in air. A third charge Q is

to be kept along the same line in such a way that the net

force acting on q and 2 q is zero. Calculate the position of

charge Q in terms of q and d.

7.Two identical points charges of charge Q are kept at a

distance r from each other. A third point charge is placed on

the line joining the above two charges such that all the three

charges are in equilibrium. Calculate the magnitude and

location of the third charge.

8.Two point charges A and B of 1.5 2.5Cand Cµ µ

respectively are kept 30 cm apart in air. Calculate electric

potential at a point C that is 10 cm from the mid point of

straight line AB and is on a plane normal to AB and passing

through mid point of this line. 9.An infinite plane sheet of charge density 10 -8 Cm

held in air. In this situation how far apart are two

equipotential surfaces, whose PD is SV?

10.An electric dipole of length 2 cm is placed with its axis

making an angle of 60 ° to a uniform electric field of 10

N/C. If it experience a torque of 8 3 Nm, Calculate the

(i) magnitude of the charge on the dipole and (ii) potential energy of the dipole.

11.Two point charges A and B of values + 5 x10

x 10 -9 C are kept 6 cm apart in air. Calculate the work done

when charge B is moved by 1 cm towards charge A.

12.Two equal charges place in air separated by a distance 3m

repel each other with force 0.1 gF. Calculate magnitude of

either of the charge.

13. Two point chares of 2x10 –7 C and 1.0 x 10 –7

apart. What is the magnitude of the field produced by either

charge at the site of the other? Use standard value of

14.Two charge 0.2 0.2Cand Cµµ µµ+ − are placed 10

apart. Calculate the electric field at an axial point at a

distance of 10 cm from their mid point .Use standard value

HOLIDAYS HOMEWORK

1.Dielectric constant of water is 80.What is its permittivity?

encloses a total charge Q .If there

2 > r 1) and

in place of air.

3 Determine the magnitude of an electric field that will

4.n small drops of same size are charged to V volts each.

They coalesce to form a bigger drop. Calculate potential of

particles

6.Two points electric charges of values q and 2 q are kept at

a distance d apart from each other in air. A third charge Q is

to be kept along the same line in such a way that the net

force acting on q and 2 q is zero. Calculate the position of

7.Two identical points charges of charge Q are kept at a

distance r from each other. A third point charge is placed on

the line joining the above two charges such that all the three

charges are in equilibrium. Calculate the magnitude and

2.5Cand Cµ µ

respectively are kept 30 cm apart in air. Calculate electric

from the mid point of

straight line AB and is on a plane normal to AB and passing

Cm - 2, is

held in air. In this situation how far apart are two

10.An electric dipole of length 2 cm is placed with its axis

to a uniform electric field of 10 5

Nm, Calculate the

11.Two point charges A and B of values + 5 x10 -9 C and + 3

C are kept 6 cm apart in air. Calculate the work done

charge A.

12.Two equal charges place in air separated by a distance 3m

repel each other with force 0.1 gF. Calculate magnitude of

7 C are 1 cm

the field produced by either

charge at the site of the other? Use standard value of 0

1

4πε.

are placed 10 – 6cm

apart. Calculate the electric field at an axial point at a

cm from their mid point .Use standard value

distance of 4 cm. Calculate the linear charge density.

16.A proton and neutron consists of three quarks each. Two

types of quarks i.e. up quark denoted by u of charge

and the down quark denoted by d of charge

with electrons build up ordinary matter .Suggest a possible

quark composition of a proton and neutron.

17.If a capacitor is disconnected from the battery, what will be the energy stored in the capacitor when (i) separation

between plates is doubled and (ii) an uncharged and

identical capacitor is connected across it.

18.The equivalent capacitance of the combination between A

and B in the given figure is 15

Fµ . Calculate value of C

19.Two capacitors 1 23 6 .C FandC Fµ µ= =

series are connected in parallel with a third capacitor

3 4 .C Fµ= The arrangement is connected to a 6 V battery.

Calculate the total energy stored in the capacitors.

20.A parallel plate capacitor with air between its plate having

plate are a of 6x10 –3

m 2 and separation between them 3mm

is connected to a 100 V supply. Calculate charge on each

plate of the capacitor. Explain what would happen when a 3

mm thick mica sheet (dielectric constant, K = 6) inserted

between the plates.

(i )While the voltage supply remains connected

(ii) After the supply is disconnected.

21.When two capacitor of capacitance C

connected in series the net capacitance is 3

connected in parallel its value is 6 µ

C1 and C 2.

22.Find the equivalent capacitance of the combination of

capacitors

between the

points. A and B

as shown in the

figure. Also calculate the total

charge that flows

in the circuit when 100 V battery is connected between

points A and B .

23.A parallel plate capacitor with air between the plates has a

capacitance of 8 pF (1 pF=10 –12

F). What will be the

capacitance if the distance between the plates is reduced by

half, and the space between them is filled with a substance

of dielectric constant 6?

24.Three capacitors each of capacitance 9 pF are connected

in series. (a) What is the total capacitance of the

combination? (b) Determine the charge on each capacitor if the combination is connected to a 120 V supply?

25.Three capacitors of capacitance 2 pF, 3 pF and 4 pF are

connected in parallel.

(a) What is the total capacitance of the combination?

Grade XII

distance of 4 cm. Calculate the linear charge density.

16.A proton and neutron consists of three quarks each. Two

types of quarks i.e. up quark denoted by u of charge 2

3e+

and the down quark denoted by d of charge 1

3e− ,together

with electrons build up ordinary matter .Suggest a possible

ton and neutron.

17.If a capacitor is disconnected from the battery, what will be the energy stored in the capacitor when (i) separation

between plates is doubled and (ii) an uncharged and

identical capacitor is connected across it.

ent capacitance of the combination between A

1 23 6 .C FandC Fµ µ= = arranged in

series are connected in parallel with a third capacitor

The arrangement is connected to a 6 V battery.

Calculate the total energy stored in the capacitors.

20.A parallel plate capacitor with air between its plate having

and separation between them 3mm is connected to a 100 V supply. Calculate charge on each

plate of the capacitor. Explain what would happen when a 3

mm thick mica sheet (dielectric constant, K = 6) inserted

(i )While the voltage supply remains connected.

(ii) After the supply is disconnected.

21.When two capacitor of capacitance C 1 and C 2 are

connected in series the net capacitance is 3 µ F; when

µ F. Calculate values of

22.Find the equivalent capacitance of the combination of

0 V battery is connected between

23.A parallel plate capacitor with air between the plates has a

F). What will be the

capacitance if the distance between the plates is reduced by

the space between them is filled with a substance

24.Three capacitors each of capacitance 9 pF are connected

in series. (a) What is the total capacitance of the

combination? (b) Determine the charge on each capacitor if he combination is connected to a 120 V supply?

25.Three capacitors of capacitance 2 pF, 3 pF and 4 pF are

(a) What is the total capacitance of the combination?

CURRENT ELECTRICITYCURRENT ELECTRICITYCURRENT ELECTRICITYCURRENT ELECTRICITY 1.A carbon resistor of 47kΩ is to be marked with rings of

different colours for its identification. Write the sequence of

the colours (Colour code). 2. A carbon resistor is marked in green, red and orange bands.

What is the approximate resistance of the resistor?

3. A carbon resistor is marked in red, yellow and orange bands.

What is the approximate resistance of the resistor?

4. A given copper wire is stretched to reduce its diameter to

half its previous value. What will be its new resistance?

5. A wire of resistance 4 R is bent in the form of a circle. What

is the effective resistance between the ends of diameter?

6. A battery of e.m.f. 10 V and internal resistance 3

connected to a resistor .If the current in the circuit is 0.5 A.

What is the resistance of the resistor? What is the terminal

voltage of the battery when the circuit closed? 7. At room temperature (27.0 C° ) the resistance of a heating

element is 100 Ω . What is the temperature of the element if

the resistance is found to be 117 Ω , given that the temperature

coefficient of the material of the resistor is 1.70x10

8. A silver wire has resistance of 2.1 Ω at 27.5 °

resistance of 2.7 Ω at 100 C° .Determine the temperature

coefficient of resistively of silver. 9A potential difference of 2v is applied between the point A

and B as shown in the network drawn in the figure. Calculate (i ) the equivalent resistance of the network across the points A and B and (ii) the magnitudes of currents flowing in the arms AFCEB and AFDEB. 10. Calculate conductivity of the material of a conductor of length 3m,area of cross 0.02 mm 2 having a resistance of 2 ohm. 11. Two wires A and B are of same metal, have the same area

of across-section and have their lengths in the ratio 2:1. What

will be the ratio of current flowing through them respectively

when the same potential difference is applied across length

of each of them? 12. a wire of uniform cross-section and length l has a

resistance of 16 Ω .It is cut into four equal parts. Each part is

stretched uniformly to length l and all four stretched parts are

connected in parallel. Calculate the total resistance of the

combination so formed. Assumed that stretching of wire

does not cause any change in the density of its material.

13. (a)Six cells each of e.m.f. 2.0 v and internal resistance of

0.015 Ω are joined in series to provide a supply to a

resistance of 8.5 Ω . What are the current drawn from the

supply and its terminal voltage? (b) A cell after long use has an e.m.f. 1.9 V and a large

internal resistance of 380 Ω . What maximum current can be

drawn from the cell? Could the cell drive the starting motor of a car? 14. (a)A storage battery is marked as having a capacity of 3.5

A h at 1 h discharge rate .What does this signify? Would

the cell provide 14A for 15 min? (b)Which type of cell would you want to use if your device

his connection by a diagram . 26.Find the value of unknown resistance X in the following

circuit, if no current flows through the section AO. Also calculate the current drawn by the circuit from

is to be marked with rings of different colours for its identification. Write the sequence of

2. A carbon resistor is marked in green, red and orange bands. What is the approximate resistance of the resistor?

3. A carbon resistor is marked in red, yellow and orange bands. What is the approximate resistance of the resistor?

wire is stretched to reduce its diameter to half its previous value. What will be its new resistance?

5. A wire of resistance 4 R is bent in the form of a circle. What is the effective resistance between the ends of diameter?

f. 10 V and internal resistance 3 Ω is connected to a resistor .If the current in the circuit is 0.5 A. What is the resistance of the resistor? What is the terminal

) the resistance of a heating

. What is the temperature of the element if

, given that the temperature

oefficient of the material of the resistor is 1.70x10 – 4

° C -1

? °c, and a

.Determine the temperature

9A potential difference of 2v is applied between the point A

material of a conductor of length 3m,area of cross-section

11. Two wires A and B are of same metal, have the same area section and have their lengths in the ratio 2:1. What

will be the ratio of current flowing through them respectively potential difference is applied across length

section and length l has a .It is cut into four equal parts. Each part is

all four stretched parts are connected in parallel. Calculate the total resistance of the combination so formed. Assumed that stretching of wire does not cause any change in the density of its material.

d internal resistance of are joined in series to provide a supply to a

. What are the current drawn from the

use has an e.m.f. 1.9 V and a large . What maximum current can be

drawn from the cell? Could the cell drive the starting motor

14. (a)A storage battery is marked as having a capacity of 3.5 A h at 1 h discharge rate .What does this signify? Would

(b)Which type of cell would you want to use if your device

26.Find the value of unknown resistance X in the following

required (i) a current of 100A for 20 s,

(ii) a current of 10 mA occasionally?

15. In a discharge tube, the number of hydrogen ions (i.e.

protons) drifting across a cross-section per second is 1.0x

10 18

, while the number of electrons drifting in the opposite direction across another cross-section is 2.7x 10

second. If the supply voltage is 230 V, what is the effective

resistance of the tube? 16. Three identical cells, each of e.m.f 2 V and internal

resistance of 0.2 Ω are connected in series to an external

resistor of 7.4 Ω . Calculate the current in the circuit.

17.A battery of em.f. 3.5 V and internal resistance r is

connected in series with a resistor of 55

ammeter of resistance 10 Ω . The ammeter

the circuit diagram and calculate the value of r.

18. Two cells of e.m.f. 6V and 12 V and internal resistance

1 Ω and 2 Ω respectively are connected in parallel so as to send current in the same direction through an external

resistance of 15 Ω . (i) Draw the circuit diagram. (ii) Using

kirchhoff’s laws calculate (a) current through each branch

(b) p.d. across 15 Ω resistance. 19. Two cells of em.f. E 1 and E2 (E

shown in figure. When a potentiometer is connected between A and B, the balancing length of the potentiometer wire is

300 cm. On connecting the same potentiometer between A

and C, the balancing length is 100 cm. Calculate the ratio of

E1 and E2. 20. Two identical cells of e.m.f. 1.5 V, each joined in parallel provide supply to an external circuit consisting

resistors of 17 Ω each joined in parallel. A very high

resistance voltmeter reads the terminal voltage of the cells to

be 1.4 V. What is the internal resistance of each cell?

21. Find equivalent resistor .

22.A 20 V battery of internal resistance 1 Ω is connected to three coils of 12 Ω ,6 Ω and 4 Ω in parallel, a resistor of 5 Ω and a reversed battery (e.m.f. 8 V and internal

resistance 2 Ω )as shown. Calculate

(i)the current in the circuit (ii) current in resistor 12 Ω coil and (iii) p.d. across each battery. 23.When two resistances are in series, they have value25 Ω and in parallel 4 Ω . Find each 24. Find resistively of a conductor in

which a current density of 2.5 A/m is found to exist; when an electric field 15V/m is

applied to it.. 25. You have 3 resistances of value R each .How will you

connect these for obtaining total resistance of

33. Figure shown a 2.0 V potentiometer used for the

determination of internal resistance

of a 1.5-v cell .The balance point of

the cell in open circuit is 76.3 cm

. When a resistor of 9.5 Ω is used in

required (i) a current of 100A for 20 s, (ii) a current of 10 mA occasionally?

15. In a discharge tube, the number of hydrogen ions (i.e. section per second is 1.0x

, while the number of electrons drifting in the opposite section is 2.7x 1018 per

second. If the supply voltage is 230 V, what is the effective

16. Three identical cells, each of e.m.f 2 V and internal are connected in series to an external

. Calculate the current in the circuit.

17.A battery of em.f. 3.5 V and internal resistance r is connected in series with a resistor of 55 Ω through an

. The ammeter reads 50mA.Draw the circuit diagram and calculate the value of r.

18. Two cells of e.m.f. 6V and 12 V and internal resistance respectively are connected in parallel so as to

ent in the same direction through an external . (i) Draw the circuit diagram. (ii) Using

kirchhoff’s laws calculate (a) current through each branch

(E 1>E2) are connected as

A and B, the balancing length of the potentiometer wire is 300 cm. On connecting the same potentiometer between A and C, the balancing length is 100 cm. Calculate the ratio of

20. Two identical cells of e.m.f. 1.5 V, each joined in parallel provide supply to an external circuit consisting of two

each joined in parallel. A very high resistance voltmeter reads the terminal voltage of the cells to be 1.4 V. What is the internal resistance of each cell?

and a reversed battery (e.m.f. 8 V and internal )as shown. Calculate

24. Find resistively of a conductor in which a current density of 2.5 A/m 2

d to exist; when an electric field 15V/m is

25. You have 3 resistances of value R each .How will you

connect these for obtaining total resistance of 3R

?.2

Show t

33. Figure shown a 2.0 V potentiometer used for the

determination of internal resistance

v cell .The balance point of

is used in

27.Four identical cells, each of e.m.f. 2 V are joined in parallel

providing supply of current to external circuit consisting of

two 15 Ω resistors joined in parallel. .The terminal voltage of

the cells, as read by an ideal voltmeter is 1.6 V .Calculate

internal resistance of each cell. 28.A battery of e.m.f. E and internal resistance r gives a

current of 0.5A with an external resistor 12 Ω and current of

0.25 A with an external resistor of 25 Ω . Calculate (i)

internal resistance of the cell and (ii) e.m.f. Of the cell.

29.find magnitude of resistance X in the circuit shown below, when no current flows through the 5 Ω resistor.

30.In the following circuit, a meter bridge is shown in its

balanced state. The meter bridge wire has a resistance of 1 Ω /cm. Calculate the value of the unknown resistance X and the current drawn from the battery of

negligible internal resistance

31.The length of a potentiometer wire is 5m .It is connected to

a battery of constant e.m.f. For a given Leclanche cell, the

position of zero galvanometer deflection is obtained at 100

cm .If the length of potentiometer wire be made 8 m instead

of 5 m, calculate the length of wire for zero deflection in

galvanometer for same cell. 32.Thre exists a constant potential difference between ends of

a potentiometer wire. Two cells are connected, in turn ,in

such a way that they help each other and area balance on the

potentiometer wire at (a) 120 cm (b) 60 cm length r

Calculate the ratio of e.m.f. of the two cells.

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27.Four identical cells, each of e.m.f. 2 V are joined in parallel providing supply of current to external circuit consisting of

resistors joined in parallel. .The terminal voltage of n ideal voltmeter is 1.6 V .Calculate

28.A battery of e.m.f. E and internal resistance r gives a and current of

. Calculate (i) internal resistance of the cell and (ii) e.m.f. Of the cell.

29.find magnitude of resistance X in the circuit shown below,

30.In the following circuit, a meter bridge is shown in its

resistance X and the current drawn from the battery of negligible internal resistance

31.The length of a potentiometer wire is 5m .It is connected to nstant e.m.f. For a given Leclanche cell, the

position of zero galvanometer deflection is obtained at 100 cm .If the length of potentiometer wire be made 8 m instead of 5 m, calculate the length of wire for zero deflection in

32.Thre exists a constant potential difference between ends of a potentiometer wire. Two cells are connected, in turn ,in such a way that they help each other and area balance on the

potentiometer wire at (a) 120 cm (b) 60 cm length respectively.

length of the potentiometer wire.

Determine the internal resistance

of the cell.

34. The length of a potentiometer wire is 600 cm and it carries

a current of 40 mA .For a cell of emf 2 V and internal resistance 10 ohm, the null point is found to be at 500 cm. If

a voltmeter is connected across the cell, the balancing length

is decreased by 10 cm. Find (i)the resistance of whole wire,

(ii) reading of the voltmeter ,and (iii) resistance of voltmeter.

35.Figure shows a potentiometer with a cell of 2.0 v and

internal resistance 0.40 Ω maintaining an potential drop

across the maintaining a potential drop across the resistor wire AB A standard cell which maintains a 8 constant e.m.f. of 1.02 v gives a balance point at 67.3 cm length of the wire . To ensure very low currents drawn from the standard cell ,a very high resistance of 600 k

Ω is put in series with it. Which is shorted close to the

balance point. The standard cell is then replaced by a cell

of unknown e.m.f. ε and the balance point found similarly,

turns out to be at 82.3 cm length of the wire.

(a) What is the value of ε ?

(b) What purpose does the high resistance of 600k

(c) Does this high resistance affect the balance point?

(d) Does the internal resistance

balance point?

(e) Would the method work in the above situation if the

driver cell of the potentiometer had an e.m.f of 1.0 V instead of 2.0 V ?

(f) Would the circuit work well for determining an

extremely small e.m.f. say of the orsuch as the typical e.m.f. of a thermo

,how will you modify the circuit?

36.As shown in the figure a variable rheostat of 2k

control the potential difference across a

500 Ω load. If resistance AB is 500

what should be potential difference

across the load? 37. In the above problem if load is removed what should be the resistance

at BC to get 40 V between B and C?

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34. The length of a potentiometer wire is 600 cm and it carries a cell of emf 2 V and internal

resistance 10 ohm, the null point is found to be at 500 cm. If a voltmeter is connected across the cell, the balancing length is decreased by 10 cm. Find (i)the resistance of whole wire,

oltmeter ,and (iii) resistance of voltmeter. 35.Figure shows a potentiometer with a cell of 2.0 v and

maintaining an potential drop

drawn from the standard cell ,a very high resistance of 600 k is put in series with it. Which is shorted close to the

balance point. The standard cell is then replaced by a cell and the balance point found similarly,

turns out to be at 82.3 cm length of the wire.

What purpose does the high resistance of 600k Ω have?

Does this high resistance affect the balance point? of the driver cell affect the

Would the method work in the above situation if the

driver cell of the potentiometer had an e.m.f of 1.0 V

Would the circuit work well for determining an

extremely small e.m.f. say of the order of a few mV ( such as the typical e.m.f. of a thermo-couple )?If not

,how will you modify the circuit? 36.As shown in the figure a variable rheostat of 2k Ω is used to

control the potential difference across a load. If resistance AB is 500 Ω ,

what should be potential difference

removed what should be the resistance at BC to get 40 V between B and C?