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.