CURRENT ELECTRICITY
Sub Topics: Introduction, Ohm’s Law, Resistance, Resistivity, Combination of
resistors – Series and Parallel, Cells, Emf.
One Word Important Question and Answers.
1. What constitutes an electric current?
Ans. Charges in motion constitutes an electric current.
2. Define electric current.
Ans. The amount of charge flowing across an area held normal to the direction of
flow of charge per unit time is called electric current.
3. Give the SI unit of current.
Ans. SI unit of current is ampere(A).
4. Define the unit of electric current. Or write the relation between coulomb and ampere.
Ans. If one coulomb of charge crosses an area normally in one second, then the current through
that area is one ampere i.e. 1 ampere = 1𝑐𝑜𝑢𝑙𝑜𝑚𝑏/1 𝑠𝑒𝑐𝑜𝑛𝑑 or 1 A = 1C s-1.
5. Is electric current being a scalar or vector quantity.
Ans. It is a scalar quantity.
6. What do you mean by steady current?
Ans. A current whose magnitude does not change with time is called steady current.
8. What do you mean by varying current?
Ans. A current whose magnitude changes with time is called varying current.
9. What does the direction of electric current signify in an electric circuit?
Ans. The direction of conventional current in an electric circuit tells the direction of flow of
positive charges in that circuit.
10. What is the net flow of electric charges in any direction inside the solid conductor?
Ans. It is zero.
11. Name the current carries in metals (solid conductors), electrolytic solutions (liquid
conductors) and discharge tubes (gaseous conductors).
, Ans. Free electrons in solid conductors, positively and negatively charged ions in liquid
conductors and positive ions and electrons in gaseous conductors.
12. State Ohm’s law.
Ans. Ohm’s law states that the current (I) flowing through a conductor is directly
proportional to the potential difference (V) applied across its ends, provided the temperature
and other physical conditions remain constant”.
i.e. I ∝ 𝑉 or V = IR
13. Define resistance.
Ans. It is defined as the ratio of the potential difference (V) across the ends of the conductor
to the electric current (I) through it.
i.e. 𝑅 = 𝑉/𝐿
14. Define the SI unit of resistance
Ans. The resistance of a conductor is I ohm if one ampere of current flows through it when
the potential difference across its ends is one volt.
15. How does the resistance of a conductor depend on length?
Ans. The resistance (R) of a conductor is directly proportional to its length (l)
i.e. R∝ 𝑙.
16. How does the resistance of a conductor depend on area of cross section of a conductor?
Ans. The resistance (R) of a conductor is inversely proportional to its area of cross section
(A).
17. Define electrical conductance.
Ans. The reciprocal of resistance is called electrical conductance.
18. Mention the SI unit of conductance.
Ans. Siemen (s)or mho(U).
19. Define resistivity of a conductor.
Ans. The resistivity of material of a conductor at a given temperature is equal to resistance of
unit length of the conductor having unit area of cross section.
20. A wire of resistivity 𝜌 is stretched to three times its length. What will be its new
resistivity?
Ans. There will be no change in its resistivity, because resistivity does not depend on length
(dimension) of wire.
21. Mention the relation between the resistance and resistivity?
Sub Topics: Introduction, Ohm’s Law, Resistance, Resistivity, Combination of
resistors – Series and Parallel, Cells, Emf.
One Word Important Question and Answers.
1. What constitutes an electric current?
Ans. Charges in motion constitutes an electric current.
2. Define electric current.
Ans. The amount of charge flowing across an area held normal to the direction of
flow of charge per unit time is called electric current.
3. Give the SI unit of current.
Ans. SI unit of current is ampere(A).
4. Define the unit of electric current. Or write the relation between coulomb and ampere.
Ans. If one coulomb of charge crosses an area normally in one second, then the current through
that area is one ampere i.e. 1 ampere = 1𝑐𝑜𝑢𝑙𝑜𝑚𝑏/1 𝑠𝑒𝑐𝑜𝑛𝑑 or 1 A = 1C s-1.
5. Is electric current being a scalar or vector quantity.
Ans. It is a scalar quantity.
6. What do you mean by steady current?
Ans. A current whose magnitude does not change with time is called steady current.
8. What do you mean by varying current?
Ans. A current whose magnitude changes with time is called varying current.
9. What does the direction of electric current signify in an electric circuit?
Ans. The direction of conventional current in an electric circuit tells the direction of flow of
positive charges in that circuit.
10. What is the net flow of electric charges in any direction inside the solid conductor?
Ans. It is zero.
11. Name the current carries in metals (solid conductors), electrolytic solutions (liquid
conductors) and discharge tubes (gaseous conductors).
, Ans. Free electrons in solid conductors, positively and negatively charged ions in liquid
conductors and positive ions and electrons in gaseous conductors.
12. State Ohm’s law.
Ans. Ohm’s law states that the current (I) flowing through a conductor is directly
proportional to the potential difference (V) applied across its ends, provided the temperature
and other physical conditions remain constant”.
i.e. I ∝ 𝑉 or V = IR
13. Define resistance.
Ans. It is defined as the ratio of the potential difference (V) across the ends of the conductor
to the electric current (I) through it.
i.e. 𝑅 = 𝑉/𝐿
14. Define the SI unit of resistance
Ans. The resistance of a conductor is I ohm if one ampere of current flows through it when
the potential difference across its ends is one volt.
15. How does the resistance of a conductor depend on length?
Ans. The resistance (R) of a conductor is directly proportional to its length (l)
i.e. R∝ 𝑙.
16. How does the resistance of a conductor depend on area of cross section of a conductor?
Ans. The resistance (R) of a conductor is inversely proportional to its area of cross section
(A).
17. Define electrical conductance.
Ans. The reciprocal of resistance is called electrical conductance.
18. Mention the SI unit of conductance.
Ans. Siemen (s)or mho(U).
19. Define resistivity of a conductor.
Ans. The resistivity of material of a conductor at a given temperature is equal to resistance of
unit length of the conductor having unit area of cross section.
20. A wire of resistivity 𝜌 is stretched to three times its length. What will be its new
resistivity?
Ans. There will be no change in its resistivity, because resistivity does not depend on length
(dimension) of wire.
21. Mention the relation between the resistance and resistivity?
