the amount of current 1 passing though a conductor is directly proportional to teh potential difference V applied across its ends provided the temperature and the physical state of the conductor, dues not change. V=IR
Limitations: Ohm's law is applicable only in case of metallic conductors when their temperature and physical state do not change.
Differentiate between e.m.f and potential difference.
1. Potential difference is smaller than e.m.f
2. Potential difference depends upon resistance.
3. Potential difference is result.
Difference between A.C and D.C current.
1. The current which changes its direction of flow again and again, is known as alternating current or A.C.
2. Current produced from A.C generator.
What is difference between cell and battery?
Cell: It is the source of e.m.f to flow the charges. Cell is a specific name of source of e.m.f in which chemical energy is converted into electrical energy.
Define unit of resistance.
When a potential of one volt is applied across the end of conductor and one ampere of current passes through it, then its resistance will be one Ohm.
Difference between conductor and insulator.
Conductor: Such a material which allows electricity to pass through it, are called conductor e.g. metals are good conductors of electricity because they have free electrons.
Describe four safety measures that should be taken in connection with the household circuit.
i. Use of fuse ii. use of earth wire iii. use of circuit breakers
iv. Use of good insulated cables.
Discuss briefly the hazards of household electricity.
The damages of the electricity for life are called electricity hazards.The voltage of 50 V or 50 ma current could fatal for life.
What is galvanometer?
It is a instrument which is used to indicate the presence of current in the circuit. It is very sensitive. Its resistance is very low. It is always connected in series in the circuit.
Can current flow in a circuit without potential difference?
No, current cannot flow without the presence of a potential difference.
Why a bird can sit harmlessly on high tension wires/
Birds cna sit harmlessly on tension wires.there is one potential but no potential difference which is necessary to flow the current.That is why the birds can sit on high tension wires safely.
The property of a substance which offers opposition to the flow of current through it is called its resistance. Its unit is Ohm
What is ammeter?
It is an instrument which is used to measure the quantity of current in the circuit..Its resistance is very low. It is always connected in series in the circuit.
What is voltmeter?
It is a instrument which is used to measure the voltage or potential difference across the appliance. It is also used the measure the e.m.f in battery. Its resistance is very high. It is always connected in parallel in the circuit.
Why does not diamond conduct electricity?
Diamond does not conduct electricity. Because it has no free electrons.
Define kilo watt hour.
The amount of energy delivered by power of one kilo watt in one hour is called kilo watt hour.
1 kilo watt = 3.6 Mj
Define potential difference.
Potential difference across the two ends of a conductor causes the dissipation electrical energy into other forms of energy as charges flow through the circuit.
Define specific resistance.
The resistance of one meter cube of a substance is equal to its specific resistance.It unit is Ohm meter .
Define electric power.
The amount of energy supplied by current in unit time is known as electric power.
Units: Its unit is watt.
P = energy/ time.
Unit is joule
Define the time period of A.C.
The time interval after which the A.C. voltage or current repeats its value is known as its time period.
Define unit of elctric current.
Unit of current is Ampere and defined as.
If one coulomb charge pass through an area in one second then current would be one Ampere. 1 Ampere = Cs-1
What is fuse?
Fuse is a safety device that is connected in series with live wire in the circuit to protect the equipments when excess of current flows.
Define electric current.give its formula.
The rate of flow of electric charge through any corss sectional area is called current.
Formula: I = Q/t
unit: Its S.I. unit is Ampere
Define conventional current.
Current flowing from positive to negative terminal of a battery due to the flow of positive charges is called conventional current.
Define electromotive force.
the energy converted from non electrical corms to electrical form when one coulomb of positive charge passes through the battery.