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Selina solutions for Class 8 Physics chapter 8 - Electricity

Selina Concise Physics - Middle School for Class 8 (2018-19 Session)

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Selina Selina Concise Physics - Middle School Class 8 (2018-19 Session)

Selina Concise Physics - Middle School for Class 8 (2018-19 Session) - Shaalaa.com

Chapter 8: Electricity

Chapter 8: Electricity solutions [Page 0]

 Write true or false 

A fuse wire has a high melting point.

Write true or false 

Flow of protons constitutes electric current.

 Write true or false

 Silver is an insulator of electricity.

Write true or false 

 S.I. unit and commercial unit of electrical energy are same.

 Write true or false

 Overloading of electric current in circuits can lead to short circuiting.

 Write true or false

 Overloading of electric current in circuits can lead to short circuiting.

 Write true or false

 All metals are insulators of electricity.

 

 Write true or false

The earth wire protects us from an electric shock.

 Write true or false 

A switch should not be touched with wet hands.

 

 Write true or false

 AH electrical appliances in a household circuit work at the same voltage.

 Write true or false 

 In a cable, the green wire is the live wire.

Write true or false

 A fuse is connected to the live wire.

 Write true or false 

 A switch is connected to the neutral wire.

 Fill in the blank

The unit in which we pay the cost of electricity is ..........

Fill in the blank

The electrical energy consumed in a house is measured by ...............

 Fill in the blank

 In a household electrical circuit, the appliance are connected in ............with the mains.

 Fill in the blank

A switch is connected to the .......... wire.

Fill in the blank

 The red colour insulated wire in a cable is the .............. wire.

 Fill in the blank

One kilowatt hour is equal to ............ joule.

Fill in the blank

 A fuse wire should have low .................

 Match the following

  Column A Column B 
Electric power  volt 
kWh joule
Electric current  volt × ampere
Electric energy  watt
watt ampere
potential difference  electrical energy

Select the correct alternative

All wires used in electric circuits should be covered with

  1.  colouring material
  2.  conducting material
  3.  an insulating material
  4.  none of the above

 Select the correct alternative

 Electric work done per unit time is

  1.  electrical energy
  2.  electric current
  3.  electric voltage
  4.  electrical power

Select the correct alternative

One kilowatt ¡s equal to

  1.  100 watt
  2.  1000 watt
  3.  10 watt
  4.  none of these

 Select the correct alternative

Fuse wire is an alloy of

  1.  tin-lead
  2.  copper-lead
  3.  tin-copper
  4.  lead-silver

 Select the correct alternative

A fuse wire should have

  1.  a low melting point
  2.  high melting point
  3.  very high melting point
  4.  none of the above

Select the correct alternative

 When switch of an electric appliance is put off, it disconnects

  1.  the live wire
  2.  the neutral wire
  3.  the earth wire
  4.  the live and the neutral wire

Select the correct alternative

The purpose of an electric meter in a house is

  1.  to give the cost of electricity directly
  2.  to give the consumption of electrical energy
  3.  to safeguard the circuit from short circuiting
  4.  to put on or off the mains.

 Select the correct alternative

If out of the two lighted bulbs in a room, one bulb suddenly fuses, then

  1.  other bulb will glow more
  2.  other bulb will glow less
  3.  other bulb will also fuse
  4.  other bulb will remain lighted unaffected.

Chapter 8: Electricity solutions [Page 0]

From where does the electricity come to our home ?

What is an electric meter ? Where is it fixed in our house ?

State the purpose of kWh meter.

For which unit do we pay our electricity bill ?

How can you check just by seeing the meter whether the electricity is in use or not ?

The diagram below in figure shows the reading on the dials of a meter. State what is its reading.

One day the meter reading is found to be 7643 units while next day, it was 7657 units. What is the consumption of electricity in a day ?

A source of potential difference V volt sends current I ampere in a circuit for time t second. Write expressions for electrical energy supplied by the source .

A source of potential difference V volt sends current I ampere in a circuit for time t second. Write expressions for electrical power spent by the source.

Name the unit in which you pay the cost of your electricity bill. How is it related to joule ?

If an appliance of power P watt is used for time t hour. How much electrical energy is consumed in kWh.

What is an electric fuse ? State its purpose in the household electrical circuit.

State one property of the material of a fuse wire.

Name the material of a fuse wire.

Can we use copper wire as a fuse wire ? Give reason.

How does a fuse protect the electric wiring (or an appliance) from being damaged ?

Which fuse wire is thick : 5 A or 15 A ?

How is M.C.B. superior to the fuse wire ?

With which wire: live or neutral is the fuse wire connected?

What do you mean by short circuiting of a circuit ?

Figure shows two ways of connecting the three bulbs A, B and C to a battery. Name the two arrangements. Which of them do you prefer to use in a household circuit ? Give a reason to support your answer.

How are the electrical appliances connected in a house circuit: in series or in parallel ? Give reason.

In the household electric circuit, if one bulb is fused in a room, the other bulbs keep glowing. Explain the reason.

State the voltage at which electricity is supplied to our houses.

Draw a labelled diagram with the necessary switches to connect a bulb, a fan and a plug socket in a room with the mains. In what arrangement will you connect them to the mains ?

State the colour coding of the three wires in a cable used for

Why is the metal covering of an electrical appliance earthed?

Chapter 8: Electricity solutions [Page 0]

An electrical appliance is rated as 60 W – 150 V.
(a) What do you understand by this statement ?
(b) How much current will flow through the appliance when in use ?

An electric iron of power 1.5 kW is used for 30 minute to press the clothes. Calculate the electrical energy consumed in  kilowatt hour 

An electric iron of power 1.5 kW is used for 30 minute to press the clothes. Calculate the electrical energy consumed in  joule.

Assuming the electric consumption per day to be 12 kWh and the rate of electricity to be ?6.25 per unit, find how much money is to be paid in a month of 30 days ?

In a premise 5 bulbs each of 100 W, 2 fans each of 60 W, 2 A.Cs each of 1.5 kW are used for 5 h per day. Find :
(a) total power consumed per day,
(b) total power consumed in 30 days,
(c) totoal electrical energy consumed in 30 days.
(d) the cost of electricity at the rate of ₹ 6.25 per unit.

Chapter 8: Electricity solutions [Page 0]

Write true or false 

The number of electrons and protons in an atom are same.

 Write true or false

If the charge is not in motion, we call it static electricity.

 Write true or false 

 Human body is a conductor of electricity.

Write true or false

When an ebonite rod is rubbed with fur, the electrons move from ebonite to fur.

 Write true or false

When, glass rod is rubbed with dry silk cloth, the electrons move from glass to silk.

Write true or false 

The cap of gold leaf electroscope is made of copper.

 Write true or false

If a glass rod rubbed with silk is brought near the cap of a negatively charged electroscope, the divergence of leaves will decrease.

Write true or false 

 In induction, a positively charged body can make an uncharged ‘ body positively charged.

 Write true or false 

 A lightning conductor saves the building from lighting.

Write true or false 

When a comb is rubbed with dry hair both comb and paper ‘ get similarly charged.

 Write true or false 

A glass rod rubbed with silk repels an ebonite rod rubbed with fur.

 Write true or false 

When a ebonite rod is rubbed with fur, the protons move from the ebonite rod to the fur.

 Write true or false

 A conductor has a large number of free electrons.

Write true or false

 An ebonite rod can be charged by touching it with a charged copper rod.

Write true or false

To find whether a body is charged or not, an uncharged electroscope is used.

 Write true or false

To find whether the charge on a body is positive or negative, an uncharged electroscope is used.

 Write true or false

 If a negatively charged rod is brought near a negatively charged pith ball electroscope, the pith ball will be stuck with the rod.

Fill in the blank

Like charges ............while unlike charges attract.

Fill in the blank

Mercury is a ............ of electricity while pure water is ............ of electricity.

Fill in the blank

An ebonite rod when rubbed with fur acquires the ............charge.

Fill in the blank

 When an uncharged conductor is brought in contact with the disc of a gold leaf electroscope, its leaves ....................

 Fill in the blank

 Charge is shared in charging a conductor by the method of ...............

Match the following

Column A  Column B
A. Two like charges   1 negative charge
B. Two unlike charges 

 2 repel 

C. Silver is a   3 insulator 
D. Silk is an   4 attract 
E. Ebonite rod  rubbed with fur acquires   5 conductor 

Select the correct alternative

When a glass rod is rubbed with dry silk cloth, the charge acquired by the silk cloth is

  1.  positive
  2.  negative
  3.  both positive and negative
  4.  none of the above

Select the correct alternative

When an ebonite rod is rubbed with fur, the rod acquires

  1.  positive charge
  2.  negative charge
  3.  no charge
  4.  none of the above

Select the correct alternative

When a negatively charged body is brought closer to another negatively charged body, then they will show

  1.  attraction
  2.  no effect
  3.  repulsion
  4.  none of the above

Select the correct alternative

Charging a conductor by bringing another charged conductor close to it without touching is called

  1.  induction
  2.  conduction
  3.  convection
  4.  radiation

Select the correct alternative

The factor responsible for charging a conductor is

  1.  transfer of protons
  2.  transfer of neutrons
  3.  transfer of electrons
  4.  transfer of both protons and electrons

Select the correct alternative

Two objects when rubbed together get charged. The charges on them are

  1.  equal and opposite
  2.  equal and similar
  3.  unequal and similar
  4.  unequal and opposite

Select the correct alternative

When a glass rod is rubbed with silk, the glass rod and the silk get charged because

  1.  electrons are transferred from the silk to the glass rod
  2.  electrons are transferred from the glass rod to the silk
  3.  protons are transferred from the silk to the glass rod
  4. protons are transferred from the glass rod to the silk

 Select the correct alternative

The conductor of electricity is

  1.  wood
  2.  glass
  3.  ebonite
  4.  human body

Select the correct alternative

A gold leaf electroscope is to be charged positively by conduction. For this

  1.  a positively charged rod is held close to near the disc of electroscope
  2.  a positively charged rod is placed in contact with the disc of electroscope
  3.  a negatively charged rod is held near the disc of electroscope
  4.  a negatively charged rod is touched with the disc of electroscope

Select the correct alternative

A glass rod rubbed with silk is touched with the disc of a negatively charged gold leaf electroscope. The divergence of leaves will

  1.  decrease
  2.  increase
  3.  remain unchanged
  4.  first decrease and then increase.

Select the correct alternative

 The rod in a gold leaf electroscope is made up of

  1.  wood
  2.  brass
  3.  glass
  4.  ebonite

Select the correct alternative

 Lightning conductor is made up of:

  1.  copper
  2.  glass
  3.  ebonite
  4.  wood

Chapter 8: Electricity solutions [Page 0]

What do you understand by electricity at rest ?

Why does a plastic comb rubbed with dry hair attract bits of paper ?

Who discovered the way of producing electricity by friction?

Name two substances which canbe charged by friction.

What are the two kinds of charges ?

A glass rod is rubbed with silk. State the kind of charge acquired by each.

An ebonite rod is rubbed with fur. State the kind of-charge acquired by each.

Describe an experiment to demonstrate that there are two r kinds of charges.

How will you show that like charges repel and unlike charges attract each other ?

A glass rod rubbed with silk is suspended near an ebonite r rod rubbed with fur. What will be your observation ? Give a reason to your answer.

An ebonite rod rubbed with fur is suspended near another ebonite rod rubbed with fur. State your observation and give a reason to support your answer.

What do you mean by conservation of charges ?

An ebonite rod is rubbed with fur. Compare the charges acquired by them.

Name three constituents of an atom and state the kind of charge on each of them.

What is the net charge on an atom ?

Briefly describe the structure of an atom.

What are free electrons ?

What causes the charging of two objects when they are rubbed together ?

In each of the following cases, state which body loses electrons:
(a) A glass rod when rubbed with silk.
(b) An ebonite rod when rubbed with fur.

A glass rod is rubbed with silk. Explain the charging of the glass rod and the silk on the basis of electron movement.

An ebonite rod is rubbed with fur. Explain the charging of the ebonite rod and the fur on the basis of electron movement.

Distinguish between conductors and insulators of electricity.

Give one example each of a conductor and an insulator of electricity.

State two ways of charging a conductor.

Name the way of charging a conductor in which the charge is shared.

Describe the method of charging a conductor by conduction.

A metal rod A is to be charged positively by using another charged rod B. What should be the kind of charge on the rod B if charging is to be done by conduction ?

Explain the charging by conduction in terms of movement of electrons.

Describe the method of charging a conductor by induction.

Explain the charging by induction in terms of movement of electrons.

Figure below shows a metal rod AB placed on an insulating stand. In figure (a) a negatively charged ebonite rod C is touched w ith the metal rod AB, while in figure (b), the negatively charged ebonite rod C is held near the rod AB. State the kind of charges at the ends A and B of the rod, in each case.

Can you charge an insulator by thg method of conduction ?

What is an electroscope ?

Name the two types of electroscopes.

Describe a pith ball electroscope. how can you use it to test whether a body is charged or uncharged ?

How will you use a pith ball electroscope to find out whether the charge on a charged body is positive or negative ?

Draw a labelled diagram of a gold leaf electroscope and describe its construction.

A positively charged glass rod is touched with the disc of an uncharged gold leaf electroscope. What will be your observation?

How will you use a gold leaf electroscope to find out whether a body is charged or uncharged ?

How will you use a gold leaf electroscope to find out whether the charge on a charged body is positive or negative ?

A negatively charged ebonite rod is touched with the disc of a negatively charged gold leaf electroscope. What will be your observation ?

When a charged rod is touched with the disc of a positively charged gold leaf electroscope, it is observed that the divergence of leaves decreases. What is the kind of charge on the rod ?

Describe Franklin’s experiment. What did he conclude from his experiment ?

What causes lightning ?

What are the effects of lightning ?

What is a lightning conductor ? How does it work ?

How is a tall building protected from damage due to lightning?

State three safety measures that you will observe in thunder storm.

Chapter 8: Electricity

Selina Selina Concise Physics - Middle School Class 8 (2018-19 Session)

Selina Concise Physics - Middle School for Class 8 (2018-19 Session) - Shaalaa.com

Selina solutions for Class 8 Physics chapter 8 - Electricity

Selina solutions for Class 8 Physics chapter 8 (Electricity) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CISCE Selina Concise Physics - Middle School for Class 8 (2018-19 Session) solutions in a manner that help students grasp basic concepts better and faster.

Further, we at Shaalaa.com are providing such solutions so that students can prepare for written exams. Selina textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Class 8 Physics chapter 8 Electricity are Household Consumption of Electric Energy (Kilowatt Hour), Concept of Live Wire, Neutral Wire and Earth Wire, Concept for Safety Components, Dangers of Electricity, Battery as a Collection of Cells Connected in Series., Concept of Static Electricity.

Using Selina Class 8 solutions Electricity exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in Selina Solutions are important questions that can be asked in the final exam. Maximum students of CISCE Class 8 prefer Selina Textbook Solutions to score more in exam.

Get the free view of chapter 8 Electricity Class 8 extra questions for Physics and can use Shaalaa.com to keep it handy for your exam preparation

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