mixed circuits sample sums for practice

progressions sums for practice all varities of sums

Find an. Sn.  10th term and 20th term from other end

resistance numericals in relation to area and length

Resistance
RESISTANCE

1.Resistance denoted by R

2.Its units are ohms

3.Definition is
obstruction to flow of charge is called resistance

4.laws of resistance
resistance is directly proportional to length of conductor
R∝L
resistance is inversely proportinal to area of the conductor
Rα1/A
RαL/A
removing proportinality constant keep a constant rho(p)
R=pl/A

5.where rho p is called as resistivity or specific resistance

6.resistance also depends on material and temperature also

7.more resistance more temperature because of more friction between electrons

8.resistivity rho p only depend on material
Not on length and area

9.resistivity
definition
Resistance of cube of one meter square area
And one meter length
When current is passing perpendicular to one of its surfaces

10.reverse of resistance is conductance and units are mho

11.reverse if resistivity is conductivity


Numericals to practice

1.find resistance of 10 m of conductor of area of cross section 2 meter square with resistivity 1.6x10power minus 10 ohm.m

2 find resistance when 2.2 m of wire of radius 1cm with p=2×10 power minus 10 ohm.m

3.find resistance if p=2.2x10 minus 12 and length 20 m with diameter 2mm

4.find resistance if p= 4.4x10 power minus 13 ohm m.of length 10 m and diameter 4mm

5.find R if p=3.14×10^minus 10 ohm.m and L= 20 m and D = 8mm

6.find R if p=2.2x10^ minus 10 ohm. M
L= 200m and D= 4mm

7.find change in resistance and resistivity if length is stretched to double its length and percentage increase in resistance

8.find change in resistance and resistivity if length is made half and area is doubled and also percentage change

9.find change in resistance and resistivity  and also percentage change in faloowing cases
A.lenth made one third and area made double
B.length made triple and radius doubled
C.lenth made one fourth and radius tripled
D.length made 10 times and diameter made double
E.lenth made two third and radius made two fifth

10..Define resistance.
On what factors resistance depends.
Find resistance when 2.2x10^-10 ohm.m resistivity of wire of length 2000 cm and diameter 4mm.

11what happens to resistance and resistivity if a wire of length l and radius r is stretched to double of its length.

12.What will be the resistivity of a metal wire of 2 m length and 0.6 mm in diameter, if the resistance of the wire is 50 Ω.

13.The resistance of an electric wire of an alloy is 10 Ω. If the thickness of wire is 0.001 meter, and length is 1 m, find its resistivity.

14.The resistivity of a metal wire is 10 x 10−8 Ω m at 20°C. Find the resistance of the same wire of 2 meter length and 0.3 mm thickness.

15.The area of cross section of wire becomes half when its length is stretched to double. How the resistance of wire is affected in new condition?

16.A wire of length 3 m and area of cross-section 1.7 × 10-6 m2 has a resistance 3 × 10-2 ohm.
a. What is the formula for resistivity of the wire and what is the unit of it
b. Calculate the resistivity of the wire

17.There are m resistor each of resistance R. First they all are connected in series and equivalent resistance is X. Now they are connected in parallel and equivalent resistance is Y.  What is the ratio of X and Y?

18.Compute the resistivity of the given material whose resistance is 2 Ω; area of cross-section and length are 25cm2 and 15 cm respectively?

19 The length and area of wire are given as 0.2 m and 0.5 m2 respectively. The resistance of that wire is 3 Ω, calculate the resistivity?

20.An electrician wishes to cut a copper wire (ρ=1.724∗10−8Ωm) that has no more than 10Ω of resistance. The wire has a radius of 0.725mm. Approximately what length of wire has a resistance equal to the maximum 10Ω ?

21 What is the resistance of a 100m length of round copper wire with a radius of 0.3mm?
ρcopper=1.68⋅10−8Ωm 

22.Two students are performing a lab using lengths of wire as resistors. The two students have wires made of the exact same material, but Student B has a wire the has twice the radius of Student A's wire. If Student B wants his wire to have the same resistance as Student A's wire, how should Student B's wire length compare to Student A's wire?

23.What will be the resistivity of a metal wire of 2 m length and 0.6 mm in diameter, if the resistance of the wire is 50 Ω.

24.The resistance of an electric wire of an alloy is 10 Ω. If the thickness of wire is 0.001 meter, and length is 1 m, find its resistivity.

25.The resistivity of a metal wire is 10 x 10−8 Ω m at 20°C. Find the resistance of the same wire of 2 meter length and 0.3 mm thickness.

26.The area of cross section of wire becomes half when its length is stretched to double. How the resistance of wire is affected in new condition?


27. Calculate the resistance of a copper wire of length 2m and area of cross section 10-6 m². Resistivity of copper is 1.7 x 10-8 Ωm

28. A copper wire of length 2m and area of cross section 1.7 x 10-6 m2 has a resistance of 2 x 10-2 ohms. Calculate the resistivity of copper.

29.. The amount of charge passing through a cell in 12 seconds is 3C. What is the current supplied by the cell?

30. A 12 V battery of a car is connected across a 4 resistor. Calculate the current passing through the resistor.

31. Resistivity of a given copper wire of length 2m is 1.7 x 10-8 Ωm. The wire is stretched so that its length becomes 4m. Find new resistivity of the copper wire.

32.. Resistance of a given wire of length ‘L’ is 3Ω. The wire is stretched uniformly such that its length becomes 2L. Find the new resistance of the stretched wire.

33.. Resistance of a given wire of length ‘L’ is 4Ω. The wire is stretched uniformly such that its length becomes 3L. Find the new resistance of the stretched wire.

34.. A copper wire has a diameter of 0.5 mm and resistivity of 1.6 x 10-8 Ωm. What will be the length of this wire to make its resistance 10Ω? How much does the resistance change if the diameter is doubled?

35.. A 6Ω resistance wire is doubled up by folding Calculate the new resistance of the wire.

36.. Calculate the resistance of an aluminium cable of length 10km and diameter 20mm if the resistivity of aluminum is 2.7 x 10-8 Ωm

37.. Calculate the area of cross section of a wire if its length is 1.0m, its resistance is 23Ω and the resistivity of the material of the wire is 1.84 x 10-6 Ωm

38. A piece of wire of resistance 20Ω is drawn out so that its length is increased to twice its original length Calculate the resistance of the wire in the new situation

39. Two cylindrical wires of the same material have their lengths in the ratio of 4 : 9. What should be the ratio of their radii so that their resistances are in the ratio of 4:1?

40. Two wires of the same metal, have the same area of cross section but their lengths in the ratio of 3 : 1. What should be the ratio of current flowing through them respectively, when the same potential difference is applied across each of their length?

41.Two wires A and B of length 30m and 10m have radii 2cm and lcm respectively. Compare the resistances of the two wires. Which will have less resistance?

ohms law work sheet and notes

OHMS LAW
1.definition
potential applied is directly proportional to current flowing in a conductor
2.V ∝ i
3,v=ir
removing proportinality constant keep a constant r
4.drawing graph between v and i we get a staright line passing through origin
5.straight line is called slope
6.slope of vi graph is called resistance
7 substances which obey ohms law are ohmice conductors
examples many metals
8.substances which do not obey ohms law are non ohmic conductors
example.transistor diode,filament,led,
9.for ohmic conductors graph is straight line
and non ohmic graph wont be straight line
10.least count of ammeter or voltmeter
formula is
least  ount= reading/divisions
11.instument which has less least counts t is best instrument

Ohm’s Law Applications

The main applications of Ohm’s law are:

To determine the voltage, resistance or current of an electric circuit.

Ohm’s law is used to maintain the desired voltage drop across the electronic components.

Ohm’s law is also used in DC ammeter and other DC shunts to divert the current.

Limitations of Ohm’s Law

Following are the limitations of Ohm’s law:

Ohm’s law is not applicable for unilateral electrical elements like diodes and transistors as they allow the current to flow through in one direction only.

For non-linear electrical elements with parameters like capacitance, resistance etc the voltage and current won’t be constant with respect to time making it difficult to use Ohm’s law.

When does Ohm’s law fail?

Ohm’s law fails to explain the behaviour of semiconductors and unilateral devices such as diodes. Ohm’s law may not give the desired results if the physical conditions such as temperature or pressure are not kept constant.

Worksheet for practice

1.find potential when current of 3 mA flows across a resistance of 1000ohms ?
2.find potential when 5 c of charge flows for 2 secs across a resistance of 4 ohms?
3.find resistance when a current of 5 amp flows across a p d of 110v?
4.find potential when 10 power 19 electrons flow for 10 seconds acoss a resistance of 12ohms?
5.find current flowing in a conductor when potential of 220v applied across a resistance of 12ohms?
6.find resistance when slope makes an angle of 30 degrees alon x axis in x y plane?
7.what happens to current if potential applied is reduced to half or doubled?
8.what potential is applied in india ?
9.what is source of potential in circuit?
10.what is use of neutral wire in along with live wire?
11.what is difference between potential and potential difference?
12.what is work done if 10 col of charge flows and 5 milli amp of current flows across 100 ohms resistance?
13.what is work done if 10 power 20 electrons flows across carrying 5 milli ampere a over 1000 ohms resistance?
14.Give an example of non-ohmic devices
Ans is transistors and diodes
15.what is slope of v-i graph gives .What is conductance and its units?
16.what instrument is used to measure resistance and how do you denote it?
17.The values of currents flowing through a given resistor of resistance R for corresponding values of potential differences v across the resistors are given below
0.5v - 1 amp
1v - 0.2 amp
1.5v - 0.3 amp
2v - 0.4 amp
2.5 v - 0 5 amp
3v - 0.6 amp
4 v - 0.8 amp
5v - 1 amp
Plot a graph between v and I and determine the reistance
18.What would you suggest to a student if while performing an experiment if while performing a experiment the pointer needle of ammeter and voltmeter do not coincide with the zero mark on the scale when circuit is open.and there is no extra ammeter and voltmeter is available in the laboratory

19.Calculate the resistance if 5 A of electric current flows through a conductor having potential difference between two points is equal to 15 V.

20.If the potential difference between the terminals of an electric motor is 220 V and an electric current of 5 A is flowing through it what will be the resistance of electric motor

21.An electric current of 15 A is flowing through an electric fan. If the potential difference between two terminals of electric fan is 240 V, what will be resistance?

22.If the resistance of an electric iron is 48 Ω and an electric current of 5 A is flowing through it, what will be the potential difference between two terminals of electric iron.

23.Calculate the potential difference between two points of a terminal, if an electric current of 10 A is flowing through it having resistance of 20Ω.

24.If the resistance between two terminals of an electric heater is 15Ω and an electric current of 15 A is flowing through it then what will be the voltage of electric current?

25.0.6A current flows through a resistor shown in figure. Voltage of two points of resistor is 12V. What is the resistance of the resistor?

26 Resistance of an electric iron 50 Ω.4.2A Current flows through the resistance. Find the voltage between two points.

27.Draw a schematic diagram of a circuit consisting of a battery of three cells of 2 V each, a 5 Ω resistor, an 8 Ω resistor, and a 12 Ω resistor, and a plug key, all connected in series.

28.cell is connected to a bulb which develops a potential difference of 24 volts across it. The current in the circuit is measured to be 4 A. Find the resistance offered by the filament of the bulb to the flow of the current.

29. Calculate the potential difference across the ends of a wire of resistance 1 ohm when a current of 3 A passes through it.

30 Calculate the current flowing through a wire of resistance 15 ohm connected to a battery of potential difference 3 volt.

31.cell of potential difference 12 V is connected to a bulb. The resistance of the filament of the bulb when it glows is 24 ohm. Find the current drawn from the cell.

32. A bulb draws current 1.5 A at 6 V. Find the resistance of filament of bulb while glowing?

33. A current 0.2 A flows in a wire of resistance 15 ohm. Find the potential difference across the ends of the wire.

34.When a 24 V battery is connected to a resistor, the current in it is 0.4 A. What is the resistance of the resistor? What would be the current through it when it is connected to a battery of 6 V?

35.R1 = 10 ohm and R2 = 5 ohm in the diagram. Cell voltage is 7.5 V

Find out (a)the equivalent resistance (b) the electric current (c) the potential difference across each resistor in the circuit shown in figure (1).

36. Two resistances of 6 ohm and 12 ohm are connected in parallel. Calculate the equivalent resistance.

37.. On 1 ohm resistor is connected in parallel to a 11 ohm resistor. What is equivalent resistance?

38.Two resistors of resistances R1 =10 ohm and R2= 20 ohm are connected in parallel. A battery supplies 6 A of current to this resistance combination as shown in figure 2. Calculate the current in each resistor.

39.. A uniform wire of resistance R is cut into two equal pieces, and these pieces are joined in parallel. What is the resistance of the combination?

40. How will you join the resistors of resistances 3 ohm, 6 ohm and 8 ohm to get an equivalent resistance of 10 ohm?

41. 3 resistors, each of resistance 12 ohm, are connected in parallel. What is the equivalent resistance?

42..In the following circuit, R1 = 15 ohm and R2=30 ohm.(a) The equivalent resistance (b)The current passing the cell and, (c) the current passing through the 30 ohm resistor in the circuit shown above.

43. R1 = 20 ohm and R2 = 15 ohm in the circuit shown in figure 4 below.
The battery cell provides 7 V.
Find the current through the circuit. Also find the potential difference across the 20 ohm resistor.

44. A metal wire of resistance 6 ohm is stretched so that its length is increased to twice its original length. Calculate its new resistance.

45. How is the resistance of a wire affected if its (a) length is doubled. (b) radius is doubled? (c) length and radius both are doubled

46. What is the current in milliamperes produced by the solar cells of a pocket calculator through which 5.00 C of charge passes in 5.00 h?

47. A total of 1200 C of charge passes through a flashlight in 1 h. What is the average current?

48.What is the current when a typical static charge of 0.125 μC moves from your finger to a metal doorknob in 0.5 μs ?

49.Find the current when 2.00 nC jumps between your comb and hair over a 0.500 – μs time interval.

50. A large lightning bolt had a 20,000-A current and moved 30.0 C of charge. What was its duration?

51.The 200-A current through a spark plug moves 0.300 mC of charge. How long does the spark last?

52.the resistance of an electric iron is 50 Ω and a current of 3.2 A flows through the resistance. Find the voltage between two points.

53.An EMF source of 8.0 V is connected to a purely resistive electrical appliance (a light bulb). An electric current of 2.0 A flows through it. Consider the conducting wires to be resistance-free. Calculate the resistance offered by the electrical appliance.

54.

kwh numericals for practice

1kwh = 3.6x10^6 j

1kwh or units = nxpxtxdays/1000

numericals to practice

1.convert 2 kwh into joules

2.find no of units consumed if 2 fans of 100 w each used daily for 10 hrs for 30 days.also find monthly bill if each unit is 2 rs

3.find units consumed in 30 days and cost of bill if each unit is 2 rs
when
2 fans of 100 w used daily for 10 hrs
3 tubes of 200 w each used daily for 20 hrs

4.find units consumed in January if each unit is 3 rs
3 bulbs of 60 w each daily for 20 hrs
4 fans of 100 w each daily for 10 hrs
1 tv of 1000 w daily for 2 hrs

5.find amount of bill in March if first 100 units cost 2 rs next 100 3 rs and thereafter each unit 5 rs
if 1 tv  of 1000 w daily for 5hrs
1 fridge of 2000w for  24 hrs
2 fans of 100 w daily for 10 hrs
3 bulbs of 60 w daily for 20 hrs

6.Compute the energy consumption in a system that consumes 190 Watts of power and works for 3 hrs a day.

7.A toy car consumes energy of 500 Watts of power if it works for 2 hrs a day using it. Calculate the energy consumption a day.

8.. A 220 V – 5 A electric lamp is used for 30 minutes. How much energy does it require?

9.A 220 V – 60 W solder is used for 4 minutes. How much energy does it require.

10.The energy used by the iron for 1 minute is 33 kJ, at a voltage of 220 volts. How large q1¹the current is in the iron.

11.Someone watches TV on average 6 hours each day. The TV is connected to a 220 Volt voltage so that the electric current flows through the TV is 0.5 Amperes. If the electric company charges $0.092 per kWh, then the cost of using electric energy for TV for 1 month (30 days) is…

12.In a house there are 4 lamps 20 Watt, 2 lamps 10 Watt, 3 lamps 40 Watt, are used 5 hours every day. If the electric company charge 0.092 per kWh, then the cost of using electric energy during 1 month (30 days) is ….

13.Calculate the electrical energy consumed in Joules if a toaster of 60 W is used for 30 minutes?

14 An electric heater of 1000 W is used for two hours in a day? What is the cost of using it for a month of 28 days, if one unit costs 3.00 rupees?

15.Calculate the electricity bill amount for a month of 30 days, if the following devices are used as specified:
a.two bulbs of 40W for six hours.
b.two tubelights of 50W for eight hours
c.A TV of 120W for six hours.
d.Give the rate of electricity is 2.50 rupees per unit?

16.qqIn a factory four bulbs of 100 W each and five fans of 110 W each operate for 12 hours daily. Calculate the units of electricity consumed? Also find the total expenditure if one unit costs 2.50 rupees?

17.geyser of 2.5kW is used for eight hours daily? Calculate the monthly consumption of electrical energy units. Also calculate the cost of electrical units consumption in a month if rate per unit is 3.50 rupees?

18.find power if 100 watts powers used for 2hrs in both kwh and Joules

19.find power if 2kw power used foe 3 hrs both in kwh and Joules

20.convert 10kwh into Joules

21.conver 36 Joules into kwh

22.Find the energy in kWh consumed in 10 hours by four devices of power 500 W each.

power. numericals 9th cbse

Power numericals

1. A machine does 192 J of work in 24 Sec. What is the power of the machine?

2.A weighting 50kg runs up a hill rising himself vertically 10m in 20Sec. Calculate power. given g = 9.8m-2

3.A weighting 50kg runs up a hill rising himself vertically 10m in 20Sec. Calculate power. given g = 9.8m-2

4.A athlete weighing 60kg runs up a staircase having 10 steps each of 1m in 30 sec. Calculate power (g = 9.8ms-2

5.The heart does 1.5 J of work in each ) heartbeat. How many times per minute does it beat if its power is 2watt?

6.
Calculate the time taken 60 w bulb to consume 3000 J of energy . (50sec.

7.horse cart system moves with velocity 36kmh-1 on the level road., then find the power of horse in term of horse power (1hp=746W) 

8 In an experiment to measure his power, a student records the time taken by him in running up a flight of steps on a staircase.

Use the following data to calculate the power of the student :

Number of steps = 28 ; Height of each step = 20 cm ; Time taken = 5.4 s.

Mass of student = 55 Kg ; Acceleration due to gravity = 9.8 m s−2

9.The power of a heart which beats 72 times in a minute is 1.2kW. Calculate the work done by heart for each beat. ( 1kJ)

10 Whenn loading a truck, a man lifts boxes of 100 N each through a height of 1.5 m.

(a) How much work does he do in lifting one box ?

(b) How much energy is transferred when one box is lifted ?

(c) If the man lifts 4 boxes per minute, at what power is he working ? (g = 10 m s−2)

11.Define 1 watt of power.

12.lamp consumes 1000 J of electrical energy in 10 s. What is its power ?

13.An electric heater is rated 1500 W. How much energy does it use in 10 hours?

14.A boy of mass 40 kg runs up flight of 50 steps each 10 cm high in 5 seconds. Find: (i) the work done by the boy. (ii) the power developed, (g = 9.8 ms-2)

15.Calculate the power of an engine required to lift 10s kg of coal per hour from a mine 360 m deep, (Take g = 10ms-2).

16.A woman pulls a bucket of water of total mass 5 kg from a well which is 10 m in 10 s. Calculate the power used by her. [Take g = 10 ms-2]

17.a) Define average power.
(b) A lamp consumes 1000 J of electrical energy in 10 s. What is its power?
(c) Give the commercial unit of energy in Joules. [SAll-2013]

18.motor boat moves at a steady speed of 4 ms – 1. Water-resistance acting on it is 4000 N. Calculate the power of its engine. (16kW)

19.A man pulls a block with a force of 300 N through 50 m in 60 s. Find the power used by him to pull the block.

20.A 50 kg man moved 25 steps up in 20 seconds. Find his power, if each step is 16 cm high. (100 W)

21.Calculate the power of a pump which can lift 200 kg of water through a height of 6 m in 10 seconds. (1200 watts)

22.How is the power related to the speed at which a body can be lifted? How many kilogrims will a man working at the power of 100 W, be able to lift at constant speed of 1 mr1 vertically? (g = 10 ms

23.A car of mass 2000 kg is lifted up a distance of 30 m by a crane in 1 minute. A second crane does the same job in 2 minutes. What is the power applied by each crane?

24 Avinash can run with a speed of 8 m/s against the frictional force of 10 N, and Kapil can move with a speed of 3 m/s against the frictional force of 25 N. Who is more powerful and why?

25.What is power? How do you differentiate kilowatt from kilowatt-hour? The Jog falls in Karnataka state are nearly 20 m high. 2000 tonnes of water falls from it in a minute. Calculate the equivalent power if all this energy can be utilized. (g = 10 ms-2)

26 A rickshaw puller pulls the rickshaw by applying a force of 100 N. If the rickaw moves with constant velocity of 36 kmh-1. Find the power of rickshaw puller. (1000w)

27.A athlete weighing 60kg runs up a staircase having 10 steps each of 1m in 30 sec. Calculate power (g = 9.8ms-1 ) (ans: 200W)

28.Calculate the time taken 60 w bulb to consume 3000 J of energy . (50sec. )

29.The power of a heart which beats 72 times in a minute is 1.2kW. Calculate the work done by heart for each beat. ( 1kJ)

30.