Selina solutions concise physics class 9 icse Solutions for Chapter 9 chapter 9 current electricity

Exercises in Chapter 9 chapter 9 current electricity Grade 9

Exercise 9A

Exercise 9B

Exercise 9C

Questions in Exercise 9A

Name one d.c. source and one a.c. source.

Distinguish between d.c. and a.c.

What is an electric cell?

What transformation of energy takes place when current is drawn from a cell?

Name the constituents of a cell

State the two kinds of cell. Give one example of each

What is a primary cell? Name two such cells

What is a secondary cell? Name one such cell

State three differences between primary and secondary cells

What do you understand by the term current? State and define its S.I. unit

How much is the charge of an electron?

n electrons flow through a cross-section of a conductor in time t. If the charge on an electron is e,

write an expression for the current in the conductor

Name the instrument used to control current in an electric circuit

In the electric circuit shown in the figure, label the parts A, B, C, D, E, and F. State the function of each part. Show in the diagram the direction of flow of current

What is the function of a key (or switch) in an electric circuit

Write symbols and state functions of each of the following components in an electric circuit

(i) Key,

(ii) Cell,

(iii) Rheostat,

(iv) Ammeter, and

(v) Voltmeter

(a) Complete the circuit given in figure by inserting between the terminals A and C, an ammeter.

(b) In the diagram mark the polarity at the terminals of the ammeter and indicate clearly the direction of flow of current in the circuit, when the circuit is complete. (c) Name and state the purpose of Rh in the circuit

What are conductors and insulators of electricity? Give two examples of each

Select conductors of electricity from the following: Copper wire, silk thread, pure water, acidulated water, human body, glass, mercury.

State two differences between a conductor and an insulator of electricity

Distinguish between a closed circuit and an open circuit, with the use of a suitable labeled diagram.

Write the condition required for a circuit to be a closed circuit

A cell is used to:

(a) Measure current in a circuit

(b) Provide current in a circuit

(c) Limit current in a circuit

(d) Prevent current in a circuit

The unit of current is:

(a) Ampere

(b) Volt

(c) Ohm

(d) Coulomb

The insulator of electricity is:

(a) Copper

(b) Acidulated water

(c) Human body

(d) Silk

A charge 0.5C passes through a cross section of a conductor in 5s. Find the current

A current of 1.5A flows through a conductor for 2.0s. What amount of charge passes through the conductor

When the starter motor of a car is switched on for 0.8s, a charge 24 C passes through the coil of the motor. Calculate the current in the coil

Questions in Exercise 9B

The figure below shows two conductors A and B. Their charges and potentials are given in the diagram. State the direction of (i) flow of electrons, and (ii) flow of current, when both the conductors are joined by a metal wire

How is the direction of flow of current between two charged conductors determined by their potentials

Explain the concept of electric potential difference in terms of work done in transferring\ the charge

Define the term potential difference

State and define the S.I. unit of potential difference

‘The potential difference between two conductors is 1 volt’. Explain the meaning of this statement

What do you understand by the term resistance

Explain why does a metal wire when connected to a cell offer resistance to the flow of current.

State and define the S.I. unit of resistance

State Ohm’s law.

How are the potential difference (V), current (I) and resistance (R) related?

The resistance of wire is 1 ohm’. Explain the meaning of this statement

How is the current flowing in a conductor changed if the resistance of the conductor is doubled keeping the potential difference across it the same?

State three factors on which the resistance of a wire depends. Explain how does the resistance depends on the factors stated by you.

How is the resistance of a wire affected if its

(a) length is doubled,

(b) radius is doubled?

State whether the resistance of filament of a bulb will decrease, remain unchanged or increase when it glows

Name the physical quantities of which the units are:

(i) Volt

(ii) Coulomb

(iii) Ohm

(iv) Ampere

Current in a circuit flows:

(a) In the direction from high potential to low potential

(b) In the direction from low potential to high potential

(c) In direction of flow of electrons

(d) In any direction

The unit of potential difference is:

(a) Ampere

(b) Volt

(c) Ohm

(d) Coulomb

On increasing the resistance in a circuit, the current in it:

(a) Decreases

(b) Increases

(c) Remains unchanged

(d) Nothing can be said

In transferring 1.5 C charge through a wire, 9 J of work is needed. Find the potential difference across the wire

A cell of potential difference 12V is connected to a bulb. The resistance of the filament of bulb when it glows is 24ᘯ. Find the current drawn from the cell

A bulb draws the current 1.5A at 6.0V. Find the resistance of the filament of the bulb while glowing

A current 0.2A flows in a wire of resistance 15ᘯ. Find the potential difference across the ends of the wire

Questions in Exercise 9C

What is meant by the efficient use of energy?

State two ways to save the energy

How does proper insulation of home save energy

Which of the following device is most efficient for lighting purpose:

LED, CFL, Fluorescent tube light, Electric bulb

Give an example to explain that the use of modern eco-friendly technologies is more efficient and less polluting

Describe three ways for the efficient use of energy.

What social initiatives must be taken for the sensitive use of energy

The most non-polluting and efficient lighting device is: