Textbook Solutions: Effects of Electric Current

 Page 1


Effects Of Electric Current 
Exercise 
Q. 1. Tell the odd one out. Give proper explanation. 
 
a. Fuse wire, bad conductor, rubber gloves, generator. 
b. Voltmeter, Ammeter, galvanometer, thermometer. 
c. Loud speaker, microphone, electric motor, magnet. 
Answer : (a) Odd one - bad conductor 
Explanation: Fuse wire, rubber gloves, and generator are related to electric current. If a 
large amount of electric current flows it produce large amount of heat so fuse wire melts 
thus stopping the flow of current. Rubber gloves do not conduct heat or electricity which 
we wear while handling electrical equipment to protect from shocks. 
The generator is based on magnetic effects of electric current which converts 
mechanical energy into electrical energy. 
But bad conductor is Not related to electric current. 
(b) Odd- Thermometer. 
Explanation: Thermometer measures heat. But ammeter, voltmeter and galvanometer 
measures electric current, potential difference, a small amount of current respectively in 
an electrical circuit. 
(c) Odd- magnet 
Explanation: Loudspeaker, microphone and electric motor works on principles of some 
effects of electric current. 
But Magnet has magnetic properties which attracts magnetic substances towards it and 
has no relation with electric current. 
Q. 2. A. Explain the construction and working of the following. Draw a neat 
diagram and label it. 
 
Electric motor 
Answer : Electric motor- It converts electrical energy into mechanical energy. 
 
Principle- When a current carrying conductor is placed normally in a magnetic field it 
experiences a force which rotates the conductor thus mechanical energy is generated. 
Page 2


Effects Of Electric Current 
Exercise 
Q. 1. Tell the odd one out. Give proper explanation. 
 
a. Fuse wire, bad conductor, rubber gloves, generator. 
b. Voltmeter, Ammeter, galvanometer, thermometer. 
c. Loud speaker, microphone, electric motor, magnet. 
Answer : (a) Odd one - bad conductor 
Explanation: Fuse wire, rubber gloves, and generator are related to electric current. If a 
large amount of electric current flows it produce large amount of heat so fuse wire melts 
thus stopping the flow of current. Rubber gloves do not conduct heat or electricity which 
we wear while handling electrical equipment to protect from shocks. 
The generator is based on magnetic effects of electric current which converts 
mechanical energy into electrical energy. 
But bad conductor is Not related to electric current. 
(b) Odd- Thermometer. 
Explanation: Thermometer measures heat. But ammeter, voltmeter and galvanometer 
measures electric current, potential difference, a small amount of current respectively in 
an electrical circuit. 
(c) Odd- magnet 
Explanation: Loudspeaker, microphone and electric motor works on principles of some 
effects of electric current. 
But Magnet has magnetic properties which attracts magnetic substances towards it and 
has no relation with electric current. 
Q. 2. A. Explain the construction and working of the following. Draw a neat 
diagram and label it. 
 
Electric motor 
Answer : Electric motor- It converts electrical energy into mechanical energy. 
 
Principle- When a current carrying conductor is placed normally in a magnetic field it 
experiences a force which rotates the conductor thus mechanical energy is generated. 
Construction- 
 
It consists of an armature coil ABCD mounted on an axle. It also consists of two split 
rings P and Q with brushes X and Y and a horse-shoe electromagnet NS with a dc 
source. 
The rectangular coil is wound around a soft iron core and is placed between two poles 
of horse-shoe electromagnet. The coil is free to rotate about its axis. The ends A and D 
are connected to two split rings P and Q which are attached with brushes X and Y 
respectively. When coil rotates split rings also rotates but brushes remain fixed at their 
position. 
Working- 
i. When current enters the coil ABCD from battery through brush X and to coil and 
finally back to brush Y the current flow in coil from A to B upwards and C to D 
downwards. 
ii. So on applying Fleming’s left-hand rule, a force is exerted on arm AB which pushes it 
downwards and forces on arm CD upwards thus rotating the coil anticlockwise. As both 
forces are equal and opposite in direction rotating the coil. 
Page 3


Effects Of Electric Current 
Exercise 
Q. 1. Tell the odd one out. Give proper explanation. 
 
a. Fuse wire, bad conductor, rubber gloves, generator. 
b. Voltmeter, Ammeter, galvanometer, thermometer. 
c. Loud speaker, microphone, electric motor, magnet. 
Answer : (a) Odd one - bad conductor 
Explanation: Fuse wire, rubber gloves, and generator are related to electric current. If a 
large amount of electric current flows it produce large amount of heat so fuse wire melts 
thus stopping the flow of current. Rubber gloves do not conduct heat or electricity which 
we wear while handling electrical equipment to protect from shocks. 
The generator is based on magnetic effects of electric current which converts 
mechanical energy into electrical energy. 
But bad conductor is Not related to electric current. 
(b) Odd- Thermometer. 
Explanation: Thermometer measures heat. But ammeter, voltmeter and galvanometer 
measures electric current, potential difference, a small amount of current respectively in 
an electrical circuit. 
(c) Odd- magnet 
Explanation: Loudspeaker, microphone and electric motor works on principles of some 
effects of electric current. 
But Magnet has magnetic properties which attracts magnetic substances towards it and 
has no relation with electric current. 
Q. 2. A. Explain the construction and working of the following. Draw a neat 
diagram and label it. 
 
Electric motor 
Answer : Electric motor- It converts electrical energy into mechanical energy. 
 
Principle- When a current carrying conductor is placed normally in a magnetic field it 
experiences a force which rotates the conductor thus mechanical energy is generated. 
Construction- 
 
It consists of an armature coil ABCD mounted on an axle. It also consists of two split 
rings P and Q with brushes X and Y and a horse-shoe electromagnet NS with a dc 
source. 
The rectangular coil is wound around a soft iron core and is placed between two poles 
of horse-shoe electromagnet. The coil is free to rotate about its axis. The ends A and D 
are connected to two split rings P and Q which are attached with brushes X and Y 
respectively. When coil rotates split rings also rotates but brushes remain fixed at their 
position. 
Working- 
i. When current enters the coil ABCD from battery through brush X and to coil and 
finally back to brush Y the current flow in coil from A to B upwards and C to D 
downwards. 
ii. So on applying Fleming’s left-hand rule, a force is exerted on arm AB which pushes it 
downwards and forces on arm CD upwards thus rotating the coil anticlockwise. As both 
forces are equal and opposite in direction rotating the coil. 
iii. After half rotation split, ring P contact with brush Y and split ring Q contact with brush 
X thus current will flow in DCBA path. 
iv. Now force acting on both arms of the coil will be reversed and coil will continue to 
rotate according to Fleming’s left-hand rule and complete the next half turn in the same 
direction. Thus the coil rotates continuously. 
Q. 2. B. Explain the construction and working of the following. Draw a neat 
diagram and label it. 
 
Electric Generator (AC) 
Answer : Electric generator AC converts mechanical energy into electrical energy. 
Principle- It works on the principle of electromagnetic induction. When coil rotates in a 
magnetic field it induces a current in the coil and direction of induced current is given by 
Fleming’s right hand rule. 
Construction- 
 
 
 
Page 4


Effects Of Electric Current 
Exercise 
Q. 1. Tell the odd one out. Give proper explanation. 
 
a. Fuse wire, bad conductor, rubber gloves, generator. 
b. Voltmeter, Ammeter, galvanometer, thermometer. 
c. Loud speaker, microphone, electric motor, magnet. 
Answer : (a) Odd one - bad conductor 
Explanation: Fuse wire, rubber gloves, and generator are related to electric current. If a 
large amount of electric current flows it produce large amount of heat so fuse wire melts 
thus stopping the flow of current. Rubber gloves do not conduct heat or electricity which 
we wear while handling electrical equipment to protect from shocks. 
The generator is based on magnetic effects of electric current which converts 
mechanical energy into electrical energy. 
But bad conductor is Not related to electric current. 
(b) Odd- Thermometer. 
Explanation: Thermometer measures heat. But ammeter, voltmeter and galvanometer 
measures electric current, potential difference, a small amount of current respectively in 
an electrical circuit. 
(c) Odd- magnet 
Explanation: Loudspeaker, microphone and electric motor works on principles of some 
effects of electric current. 
But Magnet has magnetic properties which attracts magnetic substances towards it and 
has no relation with electric current. 
Q. 2. A. Explain the construction and working of the following. Draw a neat 
diagram and label it. 
 
Electric motor 
Answer : Electric motor- It converts electrical energy into mechanical energy. 
 
Principle- When a current carrying conductor is placed normally in a magnetic field it 
experiences a force which rotates the conductor thus mechanical energy is generated. 
Construction- 
 
It consists of an armature coil ABCD mounted on an axle. It also consists of two split 
rings P and Q with brushes X and Y and a horse-shoe electromagnet NS with a dc 
source. 
The rectangular coil is wound around a soft iron core and is placed between two poles 
of horse-shoe electromagnet. The coil is free to rotate about its axis. The ends A and D 
are connected to two split rings P and Q which are attached with brushes X and Y 
respectively. When coil rotates split rings also rotates but brushes remain fixed at their 
position. 
Working- 
i. When current enters the coil ABCD from battery through brush X and to coil and 
finally back to brush Y the current flow in coil from A to B upwards and C to D 
downwards. 
ii. So on applying Fleming’s left-hand rule, a force is exerted on arm AB which pushes it 
downwards and forces on arm CD upwards thus rotating the coil anticlockwise. As both 
forces are equal and opposite in direction rotating the coil. 
iii. After half rotation split, ring P contact with brush Y and split ring Q contact with brush 
X thus current will flow in DCBA path. 
iv. Now force acting on both arms of the coil will be reversed and coil will continue to 
rotate according to Fleming’s left-hand rule and complete the next half turn in the same 
direction. Thus the coil rotates continuously. 
Q. 2. B. Explain the construction and working of the following. Draw a neat 
diagram and label it. 
 
Electric Generator (AC) 
Answer : Electric generator AC converts mechanical energy into electrical energy. 
Principle- It works on the principle of electromagnetic induction. When coil rotates in a 
magnetic field it induces a current in the coil and direction of induced current is given by 
Fleming’s right hand rule. 
Construction- 
 
 
 
It consists of a coil ABCD with two slip rings R1 and R2 connected with brushes B1 and 
B2 respectively. The coil is placed between two poles of a horse-shoe shaped 
electromagnet. Brushes are connected to a galvanometer which shows the direction of 
current in the circuit. 
Working- When coil rotates the arm AB goes up and arm CD goes downwards, so coil 
rotates in clockwise direction. Applying Fleming’s right hand rule the induced current 
which is produced is in the direction ABCD. Current flows from brush B2 to B1. After half 
rotation AB comes in place of CD and CD in place of AB thus induced current flows 
from DCBA. Now current flow from brush B1 to B2. Thus every half rotation current flow 
direction is reversed thus it is an alternating current. 
Q. 3. Electromagnetic induction means 
a. Charging of an electric conductor. 
b. Production of magnetic field due to a current flowing through a coil. 
c. Generation of a current in a coil due to relative motion between the coil and the 
magnet. 
d. Motion of the coil around the axle in an electric motor. 
Answer : C 
When there is relative motion between coil and a magnet there is change in magnetic 
field lines which induces a current in the coil. This phenomenon is called 
electromagnetic induction discovered by Michael Faraday. 
Q. 4. Explain the difference: 
 
AC generator and DC generator. 
Answer : 
 
Q. 5. Which device is used to produce electricity? Describe with a neat diagram. 
a. Electric motor 
b. Galvanometer 
c. Electric Generator (DC) 
d. Voltmeter 
Page 5


Effects Of Electric Current 
Exercise 
Q. 1. Tell the odd one out. Give proper explanation. 
 
a. Fuse wire, bad conductor, rubber gloves, generator. 
b. Voltmeter, Ammeter, galvanometer, thermometer. 
c. Loud speaker, microphone, electric motor, magnet. 
Answer : (a) Odd one - bad conductor 
Explanation: Fuse wire, rubber gloves, and generator are related to electric current. If a 
large amount of electric current flows it produce large amount of heat so fuse wire melts 
thus stopping the flow of current. Rubber gloves do not conduct heat or electricity which 
we wear while handling electrical equipment to protect from shocks. 
The generator is based on magnetic effects of electric current which converts 
mechanical energy into electrical energy. 
But bad conductor is Not related to electric current. 
(b) Odd- Thermometer. 
Explanation: Thermometer measures heat. But ammeter, voltmeter and galvanometer 
measures electric current, potential difference, a small amount of current respectively in 
an electrical circuit. 
(c) Odd- magnet 
Explanation: Loudspeaker, microphone and electric motor works on principles of some 
effects of electric current. 
But Magnet has magnetic properties which attracts magnetic substances towards it and 
has no relation with electric current. 
Q. 2. A. Explain the construction and working of the following. Draw a neat 
diagram and label it. 
 
Electric motor 
Answer : Electric motor- It converts electrical energy into mechanical energy. 
 
Principle- When a current carrying conductor is placed normally in a magnetic field it 
experiences a force which rotates the conductor thus mechanical energy is generated. 
Construction- 
 
It consists of an armature coil ABCD mounted on an axle. It also consists of two split 
rings P and Q with brushes X and Y and a horse-shoe electromagnet NS with a dc 
source. 
The rectangular coil is wound around a soft iron core and is placed between two poles 
of horse-shoe electromagnet. The coil is free to rotate about its axis. The ends A and D 
are connected to two split rings P and Q which are attached with brushes X and Y 
respectively. When coil rotates split rings also rotates but brushes remain fixed at their 
position. 
Working- 
i. When current enters the coil ABCD from battery through brush X and to coil and 
finally back to brush Y the current flow in coil from A to B upwards and C to D 
downwards. 
ii. So on applying Fleming’s left-hand rule, a force is exerted on arm AB which pushes it 
downwards and forces on arm CD upwards thus rotating the coil anticlockwise. As both 
forces are equal and opposite in direction rotating the coil. 
iii. After half rotation split, ring P contact with brush Y and split ring Q contact with brush 
X thus current will flow in DCBA path. 
iv. Now force acting on both arms of the coil will be reversed and coil will continue to 
rotate according to Fleming’s left-hand rule and complete the next half turn in the same 
direction. Thus the coil rotates continuously. 
Q. 2. B. Explain the construction and working of the following. Draw a neat 
diagram and label it. 
 
Electric Generator (AC) 
Answer : Electric generator AC converts mechanical energy into electrical energy. 
Principle- It works on the principle of electromagnetic induction. When coil rotates in a 
magnetic field it induces a current in the coil and direction of induced current is given by 
Fleming’s right hand rule. 
Construction- 
 
 
 
It consists of a coil ABCD with two slip rings R1 and R2 connected with brushes B1 and 
B2 respectively. The coil is placed between two poles of a horse-shoe shaped 
electromagnet. Brushes are connected to a galvanometer which shows the direction of 
current in the circuit. 
Working- When coil rotates the arm AB goes up and arm CD goes downwards, so coil 
rotates in clockwise direction. Applying Fleming’s right hand rule the induced current 
which is produced is in the direction ABCD. Current flows from brush B2 to B1. After half 
rotation AB comes in place of CD and CD in place of AB thus induced current flows 
from DCBA. Now current flow from brush B1 to B2. Thus every half rotation current flow 
direction is reversed thus it is an alternating current. 
Q. 3. Electromagnetic induction means 
a. Charging of an electric conductor. 
b. Production of magnetic field due to a current flowing through a coil. 
c. Generation of a current in a coil due to relative motion between the coil and the 
magnet. 
d. Motion of the coil around the axle in an electric motor. 
Answer : C 
When there is relative motion between coil and a magnet there is change in magnetic 
field lines which induces a current in the coil. This phenomenon is called 
electromagnetic induction discovered by Michael Faraday. 
Q. 4. Explain the difference: 
 
AC generator and DC generator. 
Answer : 
 
Q. 5. Which device is used to produce electricity? Describe with a neat diagram. 
a. Electric motor 
b. Galvanometer 
c. Electric Generator (DC) 
d. Voltmeter 
Answer : C 
It converts mechanical energy into electrical energy 
 
It consists of armature coil ABCD which is placed between two poles of a horse-shoe 
shaped electromagnet, two split rings S1 and S2 connected to two brushes B1 and 
B2 respectively. 
When the coil is rotated the magnetic lines changes thus induces a current in the coil. 
The direction of induced current in the arms of coil reverses after every half rotation 
which can be obtained by Fleming’s right-hand rule. Here one brush is always in contact 
with the arm moving up in the field and another brush is in contact with the arm moving 
downward. So, a unidirectional current flows in the circuit. 
Q. 6. How does the short circuit form? What is its effect? 
Answer : When live wire comes in contact with neutral wire a large amount of current 
flows through it leading to short-circuiting. The resistance of circuit becomes very small 
thus a large number of current flows leading to the production of a large amount of heat 
thus may cause electric fires. This may damage our electrical appliances. We can also 
get electric shocks thus short-circuiting is dangerous. 
Q. 7. A. Give Scientific reasons. 
 
Tungsten metal is used to make a solenoid type coil in an electric bulb.