Electricity

Question 1

What is a switch?

Answer 1

A switch makes a conducting link between the cell and the bulb.

Question 2

How is electric current expressed?

Answer 2

Electric current is expressed by the amount of charge flowing through a particular area in unit time.

Question 3

Why is the direction of positive charges taken as the direction of current?

Answer 3

In circuits using electric wires, electrons constitute the
flow of charges. However, electrons were not known at the time when the phenomena of electricity was first discovered. So, electric current was considered to be the flow of positive charges and the direction of the flow of positive charges was taken to be the direction of current. Conventionally, in an electric circuit the direction of the electric current is taken as opposite to the direction of the flow of electrons, which are negative charges.

Question 4

What is an electric circuit?

Answer 4

A continuous and closed path of an electric current is called an electric current.

Question 5

Coulomb?

Answer 5

Coulomb which is equivalent to the charge contained in nearly 6x10 to the power 18 electrons.

Question 6

An Electron charge?

Answer 6

An Electron possess a negative charge of 1.6x10 to the power -19 Coulomb.

Question 7

One Ampere?

Answer 7

One Ampere is constituted by the flow of one Coulomb of charge per second.

Question 8

Milliampere and microampere

Answer 8

Small quantities of current are expressed in milliampere( 1mA = 1/1000 Ampere or 1mA = 10 to the power -3 Ampere) and microampere( 1 microampere = 10 to the power -6 Ampere).

Question 9

Ammeter? Why should an Ammeter have very low resistance?

Answer 9

Device used to measure current, always connected in series. Since the entire current passes through the ammeter, therefore, an ammeter should have very low resistance so that it may not change the value of the current flowing in the circuit.

Question 10

How does the electric current flow?

Answer 10

The electric current flows from the positive terminal of the cell to the negative terminal of the cell through the bulb and the ammeter.

Question 11

What is electric potential difference?

Answer 11

Potential difference between two points in an electric circuit carrying some current is defined as the work done to move a unit charge from one point to the other.

Question 12

What is potential difference?

Answer 12

In a conducting metallic wire, gravity has no role in the movement of charges. Electrons move only when there is a difference of electric pressure called the potential difference.

Question 13

Current is ———————– to resistance?

Answer 13

Inversely Proportional

Question 14

A component used to regulate current without changing the voltage source is called ?

Answer 14

Variable Resistance

Question 15

In an electric circuit, a device called ——————– is often used to change the resistance in a circuit.

Answer 15

Rheostat

Question 16

How is the motion of the electrons through a conductor is retarded by its resistance?

Answer 16

Motion of electrons in an electric circuit constitutes an electric current. The electrons, however are not completely free to move within a conductor. They are restrained by the attraction of the atoms among which they move. Thus motion of electrons through a conductor is retarded by its resistance.

Question 17

A component of a given size that offers a low resistance is a ?

Answer 17

Good conductor.

Question 18

A conductor having some appreciable resistance is called a —————————- . A component of identical size that offers a higher resistance is a ———————- .
An —————- of the same size offers even higher resistance.

Answer 18

Resistance
Poor Conductor
Insulator