Q No. 1. If 0.5 C of charge pass through the wire in 10s, then what will be the value of current flowing through wire?
Answer.
Answer.
t = 10s, Q = 0.5 C and I =?
We know that Q = It and I = Q/t So, Putting value in the equation
I = Q/t , I = 0.5/10 and I = 0.05Cs-1 So,
Hence : The current flowing through the wire is 0.05Cs-1 or 50mA.
We know that Q = It and I = Q/t So, Putting value in the equation
I = Q/t , I = 0.5/10 and I = 0.05Cs-1 So,
Hence : The current flowing through the wire is 0.05Cs-1 or 50mA.
Q No. 2. What is meant by electric current? Also write its equation.
Answer.
Answer.
Current is defined as, "The rate of flow of electric charges through any cross sectional area is called current". Current is represented by letter "I". Its equation is as follows:
Its unit is Ampere (A). Current=Charge/Time or I = Q/t
Its unit is Ampere (A). Current=Charge/Time or I = Q/t
Answer.
Conventional current is defined as, "The current flowing from positive to negative terminal due to the flow of positive charges is termed as Conventional Current". It has same effect as the other current has which flows from negative to positive.
Q No. 4. Define Ampere?
Answer.
Answer.
Ampere is defined as, "The unit of the current and current will be one ampere if one coulomb of charge pass through any cross sectional are in one second". It is represented by letter "A".
Q No. 5. Write briefly the function of Galvanometer?
Answer.
Answer.
Galvanometer is very sensitive instrument and can detect small amount of current in a circuit. A current of few mile amperes is sufficient to cause full scale deflection in it. Of the connection polarity should keep in mind while use galvanometer, after suitable modification galvanometer can be converted into an ammeter.
Q No. 6. What is the difference between flow of current and flow of water?
Answer.
Answer.
The flow of current in the circuit is like the flow of water in a pipe except that a return wire is needed in order to have a complete conducting path.
Q No. 7. What is the difference between Galvanometer and Ammeter?
Answer. Difference between galvanometer and ammeter is as follows:
Answer. Difference between galvanometer and ammeter is as follows:
Galvanometer | Ammeter |
Galvanometer is a sensitive instrument and can detect small current in a circuit. Galvanometer is connected is series. So the current in the circuit is same. | A large current of the range such as 1A or 10A can be measured by means of Ammeter. Ammeter is always connected in series, so the current flowing in the circuit also pass through ammeter. |
Cell | Battery |
Cell is a single unit at the base voltage. | A battery can be single cell or multiple cells connected together |
Q No. 8. What is the difference between Cell and Battery?
Answer. Difference between cell and a battery is in question no 7:
Q No. 9. In order to measure current in a circuit, why ammeter is always connected in series?
Answer.
Answer.
Like galvanometer, ammeter is also connected in series m so the current flowing in the circuit also passes through the ammeter.
Q No. 10. Which instrument is used for measurement of Current?
Answer.
Answer.
Ammeter is used for the measurement of electric current. It always connected in series while measuring electric current.
Q No. 11. Define Potential difference and also write the name of its unit?
Answer.
Answer.
Potential difference is define as, "Potential difference across the two ends of a conductor causes the dissipation of electrical energy into other forms of energy as charge flow through the ciucuit.
Unit: The name of its unit is Volt. Such that V = w/q
Unit: The name of its unit is Volt. Such that V = w/q
Q No. 12. Define Volt?
Answer.
Answer.
The potential difference between two point will be 1 V if 1 J of energy consumed by 1 C charge while flowing between two points. As, 1V = 1JC-1
Q No. 13. Define electro motive force? Also write its S.I unit.
Answer.
Answer.
Electromotive force is defined as, “The energy supplied by a battery to a unit positive charge when it flows through the closed circuit.
Unit: Its S.I unit is Volt. 1V = 1JC-1
Unit: Its S.I unit is Volt. 1V = 1JC-1
Q No. 14. How we measure e.m.f of battery?
Answer.
Answer.
In order to measure e.m.f of the battery we connect voltmeter directly with the terminals of the battery.
Q No. 15. What is digital multimeter?
Answer.
Answer.
A digital multimeter is used to measure current resistance and potential difference.
Q No. 16. What are sources of emf? Write names of its sources?
Answer.
Answer.
Sources of emf are as follows:
i. Battery
ii. Dry cell etc.
Q No. 17. Define resistance also write the name of its unit?
Answer.
Answer.
The property of a substance which offers opposition to the flow of current in a circuit, is called as resistance.
Unit: Its S.I unit is ohm (Ω).
Unit: Its S.I unit is ohm (Ω).
Q No. 18. State ohm`s law and write its equation?
Answer.
Answer.
Ohm`s law is stated as, "The amount of current passing through a conductor is directly proportional to the potential difference applied across its ends, provided the temperature and the physical state of the conductor does not charge".
Equation: Its equation is: V = IR
Equation: Its equation is: V = IR
Q No. 19. What are the limitations of ohm`s law?
Answer.
Answer.
Limitations of ohm`s law are as follows:
i. Ohm`s law is valid only for metals (specific metals).
ii. Ohm`s law is valid if the temperature and the physical state of metals do not change.
Q No. 20. Define ohm. Also write its symbol?
Answer.
Answer.
When a potential difference of one volt is applied across the ends of a conductor and one ampere of current passes through it, thus its resistance will be one ohm. It is represented by Ω.
Q No. 21. What do you mean by ohmic and non-ohmic conductors?
Answer.
Answer.
Ohmic Conductors: The conductors that obeys ohm`s law and have a constant resistance over a large range of voltages, are said to be ohmic. For examples, most of metals.
Non-Ohmic Conductors: Materials having resistance which changes with voltage of current. For example, Thermister and filament.
Q No. 22. How do jewelers identify diamonds as real or a fake one?
Answer.
Answer.
Jewelers identify the diamonds as real or a fake one by holding it to their lips.
Q No. 23. Why does the resistance of conductors increases with increase of temperature?
Answer.
Answer.
The resistance of conductors increases with the increase in temperature. This is due to increase in the number of collisions of electrons with themselves and with the atoms of the metals.
Q No. 24. Define Resistivity?
Answer.
Answer.
Resistivity is defined as, "The resistance of conductor of one meter cube is called resistivity".
Formulae: Its formula is R = ρ L/A
Unit: Its unit is Ohm meter (Ωm).
Formulae: Its formula is R = ρ L/A
Unit: Its unit is Ohm meter (Ωm).
Q No. 25. Which metal is used as filament of electric bulb? Explain?
Answer.
Answer.
Tungsten filament is used in electric bulb. Because tungsten has the highest melting point of all metals and it does not melt even when it is glowing.
Q No. 26. State difference between Conductor and Insulator?
Answer.
Answer.
Difference between conductor and insulator is as follows:
Conductor | Insulator |
Such materials which show less resistance to the flow of current are called conductors, for example iron and copper etc. | Such materials which have a very large value of resistance to the flow of current are called insulators. For example glass, plastic etc. |
Q No. 27. How many methods of combination of resistors?
Answer.
Resistors can be combined in the following ways:
i. Series combination
ii. Parallel combination
iii. Lethal combination
Q No. 28. Write down two features of parallel combination of resistors?
Answer.
Answer.
The features of parallel combination of resistors are as follows:
i. The sum of currents in all the resistors in equal to the current supplied by the battery in parallel combination of resistors. I = I1 + I2 + I3………
ii. The voltage across each resistance in parallel potential difference is same.
Q No. 29. Write two advantages of parallel circuit of resistors?
Answer.
Answer.
Two advantages of parallel circuit of resistors:
i. Each device in the circuit receives the full battery voltage.
ii. Each device in the circuit may be turned off independently without stopping the current flowing to the other device in the circuit. This principle is used in household wiring.
Q No. 30. Define Joule`s law?
Answer.
Answer.
Joul`s law is stated as, "The amount of heat generated in a resistance due flow of charges is equal to the product of square of current I, resistance R and the time duration t.
Formulae: Its formulae is W = I2Rt.
Formulae: Its formulae is W = I2Rt.
Q No. 31. Define electric power and its unit?
Answer.
Answer.
Electric power:
Electric power is defined as the amount of energy supplied by current in unit time
is known as electric power. Its unit is watt (W).
Unit of electric power: The unit of electric power is watt which is equal to one joule per second
as, (1 Js-1).
is known as electric power. Its unit is watt (W).
Unit of electric power: The unit of electric power is watt which is equal to one joule per second
as, (1 Js-1).
Q No. 32. Define Kilowatt-hour?
Answer.
Answer.
Kilowatt-hour is defined as the amount of energy delivered by a power of one kilowatt in one hour.
Q No. 33. Prove that 36 × 105J = 3.6MJ?
Answer. 1kWh = 1000W×1h
= 1000W×(3600s)
= 36 × 105J = 3.6MJ
Answer. 1kWh = 1000W×1h
= 1000W×(3600s)
= 36 × 105J = 3.6MJ
Q No. 34. Write down the formulae to calculate the value of electricity?
Answer. Formulae to calculate electricity bill is as follows:
Cast of electricity =(Watt*Time use in Hours/1000)*Cost Per Unit
Answer. Formulae to calculate electricity bill is as follows:
Cast of electricity =(Watt*Time use in Hours/1000)*Cost Per Unit
Q No. 35. Differentiate between D.C and A.C?
Answer. Difference between D.C and A.C is as follows:
Answer. Difference between D.C and A.C is as follows:
D.C | A.C |
1. Current obtained by cells and batteries is called D.C. 2. It is uni-directional. 3. | 1. Current obtained from generators is called A.C. 2. Its direction change again and again. 3. |
Q No. 36. Describe two major hazards of electricity?
Answer. Two major hazards of electricity are as follows:
Answer. Two major hazards of electricity are as follows:
i. Electric shock which cause human death.
ii. Fire due to short circuit.
Q No. 37. Describe two causes of short circuiting?
Answer. Two causes of short circuiting are as follows:
Answer. Two causes of short circuiting are as follows:
i. Melting of wire`s insulators.
ii. When livewire and neural wires come in direct contact.
Q No. 38. Describe two reasons of cable`s insulation damage?
Answer. Two reasons of cable`s insulation damage are as follows:
Answer. Two reasons of cable`s insulation damage are as follows:
i. Too much moisture.
ii. Constant friction.
Q No. 39. What is the difference between fuse and circuit breaker?
Answer.
Answer.
Fuse | Circuit Breaker |
A fuse is a safety device that is connected in series with the livewire in the circuit to protect the equipments when excess current flow. | Circuit breaker acts as safety device like a fuse. It disconnects the supply automatically if current exceeds the normal value. |
Q No. 40. Describe two advantages of earth wire in circuits?
Answer. Two advantages are as follows:
Answer. Two advantages are as follows:
I) We will get an electric shock if the livewire inside an appliance comes loose and touches the metal casing. However, the earth terminal is connected to the metal casing, so the current goes through the earth wire instead of passing through our body and casing an electric shock.
II) A strong current passes through the earth wire because it has a very low resistance. This breaks the fuse and disconnects the appliance.
Q No. 41. Write the two methods of safe use of electricity in homes?
Answer. Two methods are as follows:
Answer. Two methods are as follows:
i. Fuses should be connected with livewire so that the appliance will not operate after the fuse has blown.
ii. Switch off the main before changing any fuse.
Q No. 42. What is the difference between Earthwire and Livewire?
Answer. Difference between Earthwire and livewire is as follows:
Earthwire | Livewire |
Earthwire carries no current or electricity. | Livewire is a high potential wire which has potential about 220V. |
