Selina Textbook Solutions: Electricity and Magnetism | Physics Class 7 ICSE PDF Download

 Page 1


Electricity and Magnetism 
Points to Remember 
?  Some materials behave in a particular manner showing magnetic properties. 
?  A freely suspended bar magnet always point in North-South direction. 
?  Like poles repel each other while unlike poles attract each other. 
?  Magnet is neutral at its centre and has maximum magnetic effects at its ends 
called the poles. 
?  Poles always exist in pairs with opposite polarities and can never be isolated. 
?  Examples of magnetic substances are :- iron, cobalt, nickel. 
?  Examples of non-magnetic substances are :- wood, plastic, aluminium, copper. 
?  The poles are not exactly the ends of the magnet but thev are slightly inside. 
?  For a given magnet, both the poles are of equal strength. 
?  Earth’s magnet has its south pole situated near the geographic north. 
?  Electromagnets are the temporary magnets which are made up of soft iron core 
with a winding of insulated copper wire. 
?  Freely suspended current carrying solenoid always rests in north- south direction. 
?  A direct current source has the fixed positive and negative terminals, e.g. a 
battery. 
?  Hans Christian Oersted discovered that if an electric current is passed through a 
conductor, a magnetic field is developed around it. 
?  The study of magnetic effects produced due to electric current is known as 
electromagnetism. 
?  The direction of magnetic field due to a straight current carrying conductor is 
obtained by any of the following rules: 
(a) Right Hand Thumb Rule. 
(b) Right Hand Cork Screw Rule. 
?  The property due to which a changing magnetic field within a closed conducting 
coil induces electric current in the coil is called electromagnetic induction. 
?  The current produced in a closed coil when magnetic lines of force rapidly change 
within it is called the induced current. 
?  The symbol for alternating current is 0. 
?  The strength of induced current can be increased by increasing the 
(a) the number of turns in the coil 
(b) strength of the magnet used 
(c) relative speed between the magnet and closed coil. 
?  We cannot think of modem life without electricity. We light our homes and other 
places of work with electricity. 
?  It is used to run electric fans, televisions, geyser, electric irons, room heaters, 
refrigerators, music system etc. 
?  Cell is a primary source of electricity. A combination of two or more cells is a 
battery. 
?  Some other sources of electricity are generator and solar cells. 
?  The path along which an electric current flows is called a circuit. 
Page 2


Electricity and Magnetism 
Points to Remember 
?  Some materials behave in a particular manner showing magnetic properties. 
?  A freely suspended bar magnet always point in North-South direction. 
?  Like poles repel each other while unlike poles attract each other. 
?  Magnet is neutral at its centre and has maximum magnetic effects at its ends 
called the poles. 
?  Poles always exist in pairs with opposite polarities and can never be isolated. 
?  Examples of magnetic substances are :- iron, cobalt, nickel. 
?  Examples of non-magnetic substances are :- wood, plastic, aluminium, copper. 
?  The poles are not exactly the ends of the magnet but thev are slightly inside. 
?  For a given magnet, both the poles are of equal strength. 
?  Earth’s magnet has its south pole situated near the geographic north. 
?  Electromagnets are the temporary magnets which are made up of soft iron core 
with a winding of insulated copper wire. 
?  Freely suspended current carrying solenoid always rests in north- south direction. 
?  A direct current source has the fixed positive and negative terminals, e.g. a 
battery. 
?  Hans Christian Oersted discovered that if an electric current is passed through a 
conductor, a magnetic field is developed around it. 
?  The study of magnetic effects produced due to electric current is known as 
electromagnetism. 
?  The direction of magnetic field due to a straight current carrying conductor is 
obtained by any of the following rules: 
(a) Right Hand Thumb Rule. 
(b) Right Hand Cork Screw Rule. 
?  The property due to which a changing magnetic field within a closed conducting 
coil induces electric current in the coil is called electromagnetic induction. 
?  The current produced in a closed coil when magnetic lines of force rapidly change 
within it is called the induced current. 
?  The symbol for alternating current is 0. 
?  The strength of induced current can be increased by increasing the 
(a) the number of turns in the coil 
(b) strength of the magnet used 
(c) relative speed between the magnet and closed coil. 
?  We cannot think of modem life without electricity. We light our homes and other 
places of work with electricity. 
?  It is used to run electric fans, televisions, geyser, electric irons, room heaters, 
refrigerators, music system etc. 
?  Cell is a primary source of electricity. A combination of two or more cells is a 
battery. 
?  Some other sources of electricity are generator and solar cells. 
?  The path along which an electric current flows is called a circuit. 
?  Electricity has the following effects 
(a) Heating effect 
(b) Magnetic effect 
(c) Chemical effect 
(d) Mechanical effect 
?  When an electric path is complete is called closed circuit and the path with a 
break is called open circuit. 
?  The substances which allow the electricity to flow through them are called 
conductors, e.g. metals, human body etc. 
?  The substances which do not allow electricity to flow through them are called 
insulators, e.g. wood, paper, glass etc. 
?  The consumption of electricity is calculated from the meter in kWh. 
?  Electric fuse is a device which limits the current in an electric circuit. 
?  All electrical appliances are connected in parallel in household circuits. 
?  We should be cautious in using electricity. Certain precautions should be taken 
before working on an electrical gadget or circuit. 
Activity 6 
List five such electrical gadgets in your house in which electromagnet is used. 
1. …………………… 
2. …………………… 
3. …………………… 
4. …………………… 
5. …………………… 
Answer. 
1. Computer 
2. Electric motor 
3. Fan, Toaster 
4. Refrigerator 
5. Television 
6. Electric Bell 
Activity 9 
Page 3


Electricity and Magnetism 
Points to Remember 
?  Some materials behave in a particular manner showing magnetic properties. 
?  A freely suspended bar magnet always point in North-South direction. 
?  Like poles repel each other while unlike poles attract each other. 
?  Magnet is neutral at its centre and has maximum magnetic effects at its ends 
called the poles. 
?  Poles always exist in pairs with opposite polarities and can never be isolated. 
?  Examples of magnetic substances are :- iron, cobalt, nickel. 
?  Examples of non-magnetic substances are :- wood, plastic, aluminium, copper. 
?  The poles are not exactly the ends of the magnet but thev are slightly inside. 
?  For a given magnet, both the poles are of equal strength. 
?  Earth’s magnet has its south pole situated near the geographic north. 
?  Electromagnets are the temporary magnets which are made up of soft iron core 
with a winding of insulated copper wire. 
?  Freely suspended current carrying solenoid always rests in north- south direction. 
?  A direct current source has the fixed positive and negative terminals, e.g. a 
battery. 
?  Hans Christian Oersted discovered that if an electric current is passed through a 
conductor, a magnetic field is developed around it. 
?  The study of magnetic effects produced due to electric current is known as 
electromagnetism. 
?  The direction of magnetic field due to a straight current carrying conductor is 
obtained by any of the following rules: 
(a) Right Hand Thumb Rule. 
(b) Right Hand Cork Screw Rule. 
?  The property due to which a changing magnetic field within a closed conducting 
coil induces electric current in the coil is called electromagnetic induction. 
?  The current produced in a closed coil when magnetic lines of force rapidly change 
within it is called the induced current. 
?  The symbol for alternating current is 0. 
?  The strength of induced current can be increased by increasing the 
(a) the number of turns in the coil 
(b) strength of the magnet used 
(c) relative speed between the magnet and closed coil. 
?  We cannot think of modem life without electricity. We light our homes and other 
places of work with electricity. 
?  It is used to run electric fans, televisions, geyser, electric irons, room heaters, 
refrigerators, music system etc. 
?  Cell is a primary source of electricity. A combination of two or more cells is a 
battery. 
?  Some other sources of electricity are generator and solar cells. 
?  The path along which an electric current flows is called a circuit. 
?  Electricity has the following effects 
(a) Heating effect 
(b) Magnetic effect 
(c) Chemical effect 
(d) Mechanical effect 
?  When an electric path is complete is called closed circuit and the path with a 
break is called open circuit. 
?  The substances which allow the electricity to flow through them are called 
conductors, e.g. metals, human body etc. 
?  The substances which do not allow electricity to flow through them are called 
insulators, e.g. wood, paper, glass etc. 
?  The consumption of electricity is calculated from the meter in kWh. 
?  Electric fuse is a device which limits the current in an electric circuit. 
?  All electrical appliances are connected in parallel in household circuits. 
?  We should be cautious in using electricity. Certain precautions should be taken 
before working on an electrical gadget or circuit. 
Activity 6 
List five such electrical gadgets in your house in which electromagnet is used. 
1. …………………… 
2. …………………… 
3. …………………… 
4. …………………… 
5. …………………… 
Answer. 
1. Computer 
2. Electric motor 
3. Fan, Toaster 
4. Refrigerator 
5. Television 
6. Electric Bell 
Activity 9 
 
Answer. 
 
 
  
Test Yourself 
A. Objective Questions  
1. Write true or false for each statement 
(a) A current carrying coil when suspended freely can rest in any direction. 
Answer. False. 
(b) A coil carrying current behaves like a magnet. 
Answer. True. 
Page 4


Electricity and Magnetism 
Points to Remember 
?  Some materials behave in a particular manner showing magnetic properties. 
?  A freely suspended bar magnet always point in North-South direction. 
?  Like poles repel each other while unlike poles attract each other. 
?  Magnet is neutral at its centre and has maximum magnetic effects at its ends 
called the poles. 
?  Poles always exist in pairs with opposite polarities and can never be isolated. 
?  Examples of magnetic substances are :- iron, cobalt, nickel. 
?  Examples of non-magnetic substances are :- wood, plastic, aluminium, copper. 
?  The poles are not exactly the ends of the magnet but thev are slightly inside. 
?  For a given magnet, both the poles are of equal strength. 
?  Earth’s magnet has its south pole situated near the geographic north. 
?  Electromagnets are the temporary magnets which are made up of soft iron core 
with a winding of insulated copper wire. 
?  Freely suspended current carrying solenoid always rests in north- south direction. 
?  A direct current source has the fixed positive and negative terminals, e.g. a 
battery. 
?  Hans Christian Oersted discovered that if an electric current is passed through a 
conductor, a magnetic field is developed around it. 
?  The study of magnetic effects produced due to electric current is known as 
electromagnetism. 
?  The direction of magnetic field due to a straight current carrying conductor is 
obtained by any of the following rules: 
(a) Right Hand Thumb Rule. 
(b) Right Hand Cork Screw Rule. 
?  The property due to which a changing magnetic field within a closed conducting 
coil induces electric current in the coil is called electromagnetic induction. 
?  The current produced in a closed coil when magnetic lines of force rapidly change 
within it is called the induced current. 
?  The symbol for alternating current is 0. 
?  The strength of induced current can be increased by increasing the 
(a) the number of turns in the coil 
(b) strength of the magnet used 
(c) relative speed between the magnet and closed coil. 
?  We cannot think of modem life without electricity. We light our homes and other 
places of work with electricity. 
?  It is used to run electric fans, televisions, geyser, electric irons, room heaters, 
refrigerators, music system etc. 
?  Cell is a primary source of electricity. A combination of two or more cells is a 
battery. 
?  Some other sources of electricity are generator and solar cells. 
?  The path along which an electric current flows is called a circuit. 
?  Electricity has the following effects 
(a) Heating effect 
(b) Magnetic effect 
(c) Chemical effect 
(d) Mechanical effect 
?  When an electric path is complete is called closed circuit and the path with a 
break is called open circuit. 
?  The substances which allow the electricity to flow through them are called 
conductors, e.g. metals, human body etc. 
?  The substances which do not allow electricity to flow through them are called 
insulators, e.g. wood, paper, glass etc. 
?  The consumption of electricity is calculated from the meter in kWh. 
?  Electric fuse is a device which limits the current in an electric circuit. 
?  All electrical appliances are connected in parallel in household circuits. 
?  We should be cautious in using electricity. Certain precautions should be taken 
before working on an electrical gadget or circuit. 
Activity 6 
List five such electrical gadgets in your house in which electromagnet is used. 
1. …………………… 
2. …………………… 
3. …………………… 
4. …………………… 
5. …………………… 
Answer. 
1. Computer 
2. Electric motor 
3. Fan, Toaster 
4. Refrigerator 
5. Television 
6. Electric Bell 
Activity 9 
 
Answer. 
 
 
  
Test Yourself 
A. Objective Questions  
1. Write true or false for each statement 
(a) A current carrying coil when suspended freely can rest in any direction. 
Answer. False. 
(b) A coil carrying current behaves like a magnet. 
Answer. True. 
(c) In an electromagnet, the core is made up of copper. 
Answer. False. 
(d) An electric bell uses an electromagnet. 
Answer. True. 
(e) An electromagnet with soft iron core is a temporary magnet. 
Answer. True. 
(f) We use cell as the source of electricity to run an electric immersion rod. 
Answer. False. 
(g) A torch bulb glows if the terminals of the bulb are connected to the terminals of a cell 
by the metallic wire. 
Answer. True. 
(h) Wool is a conductor of electricity. 
Answer. False. 
Wool is a insulator of electricity. 
(i) Silver is an insulator of electricity. 
Answer. False. 
Silver is good conductor of electricity. 
(j) Our body is a conductor of electricity. 
Answer. True. 
(k) For a circuit to be complete, every part of it must be made up of conductors. 
Answer. True. 
(l) All metals are conductors of electricity. 
Answer. True. 
(m) The switch should not be touched with wet hands. 
Answer. True. 
(n) A switch is an on-off device in an electric circuit. 
Answer. True. 
 
Page 5


Electricity and Magnetism 
Points to Remember 
?  Some materials behave in a particular manner showing magnetic properties. 
?  A freely suspended bar magnet always point in North-South direction. 
?  Like poles repel each other while unlike poles attract each other. 
?  Magnet is neutral at its centre and has maximum magnetic effects at its ends 
called the poles. 
?  Poles always exist in pairs with opposite polarities and can never be isolated. 
?  Examples of magnetic substances are :- iron, cobalt, nickel. 
?  Examples of non-magnetic substances are :- wood, plastic, aluminium, copper. 
?  The poles are not exactly the ends of the magnet but thev are slightly inside. 
?  For a given magnet, both the poles are of equal strength. 
?  Earth’s magnet has its south pole situated near the geographic north. 
?  Electromagnets are the temporary magnets which are made up of soft iron core 
with a winding of insulated copper wire. 
?  Freely suspended current carrying solenoid always rests in north- south direction. 
?  A direct current source has the fixed positive and negative terminals, e.g. a 
battery. 
?  Hans Christian Oersted discovered that if an electric current is passed through a 
conductor, a magnetic field is developed around it. 
?  The study of magnetic effects produced due to electric current is known as 
electromagnetism. 
?  The direction of magnetic field due to a straight current carrying conductor is 
obtained by any of the following rules: 
(a) Right Hand Thumb Rule. 
(b) Right Hand Cork Screw Rule. 
?  The property due to which a changing magnetic field within a closed conducting 
coil induces electric current in the coil is called electromagnetic induction. 
?  The current produced in a closed coil when magnetic lines of force rapidly change 
within it is called the induced current. 
?  The symbol for alternating current is 0. 
?  The strength of induced current can be increased by increasing the 
(a) the number of turns in the coil 
(b) strength of the magnet used 
(c) relative speed between the magnet and closed coil. 
?  We cannot think of modem life without electricity. We light our homes and other 
places of work with electricity. 
?  It is used to run electric fans, televisions, geyser, electric irons, room heaters, 
refrigerators, music system etc. 
?  Cell is a primary source of electricity. A combination of two or more cells is a 
battery. 
?  Some other sources of electricity are generator and solar cells. 
?  The path along which an electric current flows is called a circuit. 
?  Electricity has the following effects 
(a) Heating effect 
(b) Magnetic effect 
(c) Chemical effect 
(d) Mechanical effect 
?  When an electric path is complete is called closed circuit and the path with a 
break is called open circuit. 
?  The substances which allow the electricity to flow through them are called 
conductors, e.g. metals, human body etc. 
?  The substances which do not allow electricity to flow through them are called 
insulators, e.g. wood, paper, glass etc. 
?  The consumption of electricity is calculated from the meter in kWh. 
?  Electric fuse is a device which limits the current in an electric circuit. 
?  All electrical appliances are connected in parallel in household circuits. 
?  We should be cautious in using electricity. Certain precautions should be taken 
before working on an electrical gadget or circuit. 
Activity 6 
List five such electrical gadgets in your house in which electromagnet is used. 
1. …………………… 
2. …………………… 
3. …………………… 
4. …………………… 
5. …………………… 
Answer. 
1. Computer 
2. Electric motor 
3. Fan, Toaster 
4. Refrigerator 
5. Television 
6. Electric Bell 
Activity 9 
 
Answer. 
 
 
  
Test Yourself 
A. Objective Questions  
1. Write true or false for each statement 
(a) A current carrying coil when suspended freely can rest in any direction. 
Answer. False. 
(b) A coil carrying current behaves like a magnet. 
Answer. True. 
(c) In an electromagnet, the core is made up of copper. 
Answer. False. 
(d) An electric bell uses an electromagnet. 
Answer. True. 
(e) An electromagnet with soft iron core is a temporary magnet. 
Answer. True. 
(f) We use cell as the source of electricity to run an electric immersion rod. 
Answer. False. 
(g) A torch bulb glows if the terminals of the bulb are connected to the terminals of a cell 
by the metallic wire. 
Answer. True. 
(h) Wool is a conductor of electricity. 
Answer. False. 
Wool is a insulator of electricity. 
(i) Silver is an insulator of electricity. 
Answer. False. 
Silver is good conductor of electricity. 
(j) Our body is a conductor of electricity. 
Answer. True. 
(k) For a circuit to be complete, every part of it must be made up of conductors. 
Answer. True. 
(l) All metals are conductors of electricity. 
Answer. True. 
(m) The switch should not be touched with wet hands. 
Answer. True. 
(n) A switch is an on-off device in an electric circuit. 
Answer. True. 
 
2. Fill in the blanks 
(a) A magnet has two poles. 
(b) Like poles repel each other and unlike poles attract. 
(c) An electromagnet is used to separate large mass of iron scrap. 
(d) The strength of magnetic field of an electromagnet is increased by inserting a core 
of soft iron. 
(e) In a torch we use dry cell as the source of electricity. 
(f) To light a table lamp and to run a refrigerator, we use mains as the source of 
electricity. 
(g) A group of two or more cells is called a battery. 
(h) Conductors pass electricity through them. 
(i) Insulators do not pass electricity through them. 
3. Match the following 
 
4. Select the correct alternative 
(a) A freely suspended magnet rests in 
1.  east-west direction 
2.  north-south direction 
3.  north-east direction 
4.  north-west direction.