Current Electricity

Question 1

What is the SI unit of charge

Answer 1

Coulomb

Question 2

What is the definition of current

Answer 2

Current is defined as the rate of flow of charge

Question 3

What is the SI unit of current

Answer 3

Ampere

Question 4

Define potential

Answer 4

Potential at a point is defined as the amount of work done for unit charge in bringing a positive test charge from infinity to that point

Question 5

Define potential difference

Answer 5

The potential difference between two points is equal to the work done Per unit charge in moving the positive test charge from 1.2 other

Question 6

The relationship between volt Joule and coulomb

Answer 6

One volt is equals to 1 joule per coulomb

Question 7

State the Ohm’s law

Answer 7

According to the Ohm’s law the current flowing in a conductor is directly proportional to the potential difference applied across its provided that the physical conditions on the temperature of the conductor remains constant

Question 8

Formula relating to Ohm’s law

Answer 8

V = IR

Question 9

Define resistance state its unit

Answer 9

The obstruction offered to the flow of current by conductor is called resistance its unit is ohm

Question 10

Define conductance

Answer 10

Conductance is the reciprocal of resistance

Question 11

State the limitations of the Ohm’s law

Answer 11

Ohm’s law is obeyed only when the temperature of the conductor remains constant the Ohm’s law does not work in a semiconductor

Question 12

Differentiate between ohmic resistors and non ohmic resistors give example of such materials

Answer 12

Homemade resistors follow the Ohm’s law non ohmic resistor does not obey the Ohm’s law example of a ohmic resistor is silver iron copper nichrome example of a non ohmic resistor is LED transistor filament of bulb

Question 13

State the factors affecting the resistance of a conductor

Answer 13

The material of the conductor the length of the conductor and the thickness of the conductor temperature of the conductor where are is directly proportional to length are is indirectly proportional to area of cross section directly proportional to temperature

Question 14

Define specific resistance and give the formula related to it also state its unit

Answer 14

Specific resistance of a material is the resistance of a wire of that material of unit length and unit area of cross section its unit is ohm metre.

Formula relating it is
R =p * l / a
R=p * l / pi*r²

Question 15

Define conductivity give its unit

Answer 15

The reciprocal of specific resistance is known as conductivity it is represented by the symbol Sigma its unit is one by ohm metre

Question 16

Define a fuse wire

Answer 16

It is made up of alloy of lead and tin because its melting point is low it permits current up to its save limit to pass through it but an excessive current merit its so that it blows of and the circuit is broken it is connected to the main wire

Question 17

Why is alloy of lead and Tin used for making a fuse wire

Answer 17

Alloys of lead and Tin used for making fuse wire because it’s melting point is low and specific resistance is more than that of copper or aluminium so that the resistance of short and thin fuse wire is more than that of the connecting wire

Question 18

What is used as a filament of an electric bulb and why

Answer 18

A tungsten wire is used because it has a high melting point and it close to provide light without melting

Question 19

What type of wire is used in heater toaster an ovens and why

Answer 19

Nichrome wire is used because the specific resistance of nichrome high and its resistance increases to a great extent with the increase in temperature

Question 20

Define superconductor

Answer 20

Superconductor is a substance of zero resistance at a very low temperature

Question 21

Define EMF and state it’s unit

Answer 21

When no current is drawn from a cell the potential difference produced by the chemical reaction between the terminals of the cell is called electromotive force or EMF

Question 22

Define The Terminal voltage of a cell

Answer 22

When current is drawn from a cell the potential difference between the electrodes of the cell is known as its terminal voltage

Question 23

Differentiate between EMF of a cell and terminal voltage of a cell

Answer 23

Book se dekh lo

Question 24

Factors affecting the internal resistance of a cell

Answer 24

The surface area of the electrodes the distance between the electrodes the natural concentration of the electrolyte the temperature of the electrolyte

Question 25

Formula for the combination of parallel resistors

Answer 25

1/R = 1/r¹ + 1/ r²…….

Question 26

State the formula which is used to express the amount of energy spent

Answer 26

W = i²rt
W = vit

Unit = joule (j)

Question 27

Formula relating to electrical power and its expression

Answer 27

P = vI
P= v²/r
P= i²r

Question 28

Convert 1 kwh to Joule

Answer 28

1 kwh = 3.6 x 10⁶ joule

Question 29

1 w h is equals to how many joules

Answer 29

3600 joules

Question 30

Factors that effect the heating effect of current

Answer 30

1)The amount of current passing through the wire

H o< i²

2)the resistance of the wire

       H o< R

3)the time for which current is passed in the wire

          H o< t

Therefore, H =( 0.24) i²rt