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46
Curiosity — Textbook of Science for Grade 8
Electricity: Magnetic 
and Heating Effects
4
 z If we don’t have an electric lamp while making an electric circuit 
with an electric cell, is there any other way through which we 
can find out if current is flowing in the circuit?
 z Is it possible to make temporary magnets? How can these 
be made?
 z We can generate heat by burning fossil fuels and wood; but how 
is heat generated in various electrical appliances?
 z How do we know if a cell or a battery is dead? Can all 
cells and batteries be recharged?
 z Share your questions  
  ?
Probe and ponder
Chapter 4.indd   46 Chapter 4.indd   46 6/28/2025   3:49:31 PM 6/28/2025   3:49:31 PM
Page 2


46
Curiosity — Textbook of Science for Grade 8
Electricity: Magnetic 
and Heating Effects
4
 z If we don’t have an electric lamp while making an electric circuit 
with an electric cell, is there any other way through which we 
can find out if current is flowing in the circuit?
 z Is it possible to make temporary magnets? How can these 
be made?
 z We can generate heat by burning fossil fuels and wood; but how 
is heat generated in various electrical appliances?
 z How do we know if a cell or a battery is dead? Can all 
cells and batteries be recharged?
 z Share your questions  
  ?
Probe and ponder
Chapter 4.indd   46 Chapter 4.indd   46 6/28/2025   3:49:31 PM 6/28/2025   3:49:31 PM
Chapter 4?—?Electricity: Magnetic and Heating Effects
47
It was the day of the science exhibition, and the school was 
buzzing with energy. Mohini and Aakarsh, along with their 
friends, went from one exhibit to another, eagerly exploring 
different models, asking questions and taking notes. One simple 
model really fascinated them. It was a working model of a lifting 
electromagnet which was displayed by their senior, Sumana. 
In it, instead of a hook like a typical crane, there was an iron 
nail wrapped with a wire, which was connected to a battery. 
When Sumana closed the circuit, the nail picked up iron paper 
clips like a magnet. When she opened the circuit, the clips fell 
off. Mohini and Aakarsh, were surprised. They remembered 
learning earlier (in the chapter ‘Exploring Magnets’, Curiosity, 
Grade 6) that magnetic materials were attracted by magnet and 
that iron was a magnetic material. But in Sumana’s model, there 
was no magnet, only an electric circuit. They were so excited that 
they wanted to try it out themselves.
4.1  Does an Electric Current Have a Magnetic 
Effect? 
Activity 4.1: Let us investigate
 z Collect a magnetic compass, an electric cell, a cell holder, 
two drawing pins, a safety pin, two nails, two pieces of 
connecting wires (one longer and one shorter), and two 
small pieces of cardboard. 
 z Using two drawing pins, a safety pin, and a cardboard 
piece, make a switch (as you made it earlier in the 
chapter ‘Electricity: Circuits and their Components’ in 
Curiosity, Grade 7).
 z Place the cell in the cell holder. 
 z Fix two nails to a piece of cardboard as shown in 
Fig. 4.1a. Fix the middle portion of the longer wire 
stretched between the nails, such that it is slightly above 
the surface of the cardboard. Attach one end of that 
wire to the cell holder and another end to the switch.
 z Connect the second wire between the cell holder and 
the switch.
 z Place the magnetic compass beneath the wire between 
the two nails (Fig. 4.1a). 
Fig. 4.1: An electric circuit 
and a magnetic compass
(b)
(a)
Chapter 4.indd   47 Chapter 4.indd   47 6/28/2025   3:49:32 PM 6/28/2025   3:49:32 PM
Page 3


46
Curiosity — Textbook of Science for Grade 8
Electricity: Magnetic 
and Heating Effects
4
 z If we don’t have an electric lamp while making an electric circuit 
with an electric cell, is there any other way through which we 
can find out if current is flowing in the circuit?
 z Is it possible to make temporary magnets? How can these 
be made?
 z We can generate heat by burning fossil fuels and wood; but how 
is heat generated in various electrical appliances?
 z How do we know if a cell or a battery is dead? Can all 
cells and batteries be recharged?
 z Share your questions  
  ?
Probe and ponder
Chapter 4.indd   46 Chapter 4.indd   46 6/28/2025   3:49:31 PM 6/28/2025   3:49:31 PM
Chapter 4?—?Electricity: Magnetic and Heating Effects
47
It was the day of the science exhibition, and the school was 
buzzing with energy. Mohini and Aakarsh, along with their 
friends, went from one exhibit to another, eagerly exploring 
different models, asking questions and taking notes. One simple 
model really fascinated them. It was a working model of a lifting 
electromagnet which was displayed by their senior, Sumana. 
In it, instead of a hook like a typical crane, there was an iron 
nail wrapped with a wire, which was connected to a battery. 
When Sumana closed the circuit, the nail picked up iron paper 
clips like a magnet. When she opened the circuit, the clips fell 
off. Mohini and Aakarsh, were surprised. They remembered 
learning earlier (in the chapter ‘Exploring Magnets’, Curiosity, 
Grade 6) that magnetic materials were attracted by magnet and 
that iron was a magnetic material. But in Sumana’s model, there 
was no magnet, only an electric circuit. They were so excited that 
they wanted to try it out themselves.
4.1  Does an Electric Current Have a Magnetic 
Effect? 
Activity 4.1: Let us investigate
 z Collect a magnetic compass, an electric cell, a cell holder, 
two drawing pins, a safety pin, two nails, two pieces of 
connecting wires (one longer and one shorter), and two 
small pieces of cardboard. 
 z Using two drawing pins, a safety pin, and a cardboard 
piece, make a switch (as you made it earlier in the 
chapter ‘Electricity: Circuits and their Components’ in 
Curiosity, Grade 7).
 z Place the cell in the cell holder. 
 z Fix two nails to a piece of cardboard as shown in 
Fig. 4.1a. Fix the middle portion of the longer wire 
stretched between the nails, such that it is slightly above 
the surface of the cardboard. Attach one end of that 
wire to the cell holder and another end to the switch.
 z Connect the second wire between the cell holder and 
the switch.
 z Place the magnetic compass beneath the wire between 
the two nails (Fig. 4.1a). 
Fig. 4.1: An electric circuit 
and a magnetic compass
(b)
(a)
Chapter 4.indd   47 Chapter 4.indd   47 6/28/2025   3:49:32 PM 6/28/2025   3:49:32 PM
48
Curiosity — Textbook of Science for Grade 8
While watching the compass needle, move the switch to 
‘ON’ position to allow electric current to flow through the wire 
(Fig. 4.1b). What do you observe? 
 z Now again while watching the compass needle, move the 
switch to ‘OFF’ position. What do you observe this time? 
 z Move the switch between ‘ON’ and ‘OFF’ positions a few more 
times. Carefully observe how the compass needle behaves 
the each time.
You may have noticed that when the current flows, the compass 
needle gets deflected from its original direction. When the current 
stops, the needle returns to its original direction. 
As we have learnt earlier (in the chapter ‘Exploring Magnets’ 
in Curiosity, Grade 6), the compass needle is a tiny magnet which 
deflects when a magnet is brought near it and this magnetic effect 
can act through any non-magnetic materials kept in between. 
But why does the compass needle deflect when the current 
flows through the wire? The deflection indicates that the current 
carrying wire has a magnetic effect on the compass needle. 
When the current stops, this magnetic effect disappears and 
the compass needle returns to its original direction. The region 
around a magnet or a current carrying wire where its magnetic 
effect can be felt, such as by the deflection of a compass needle, 
is said to have a magnetic field.
When electric current flows 
through a conductor (like a wire), it 
produces a magnetic field around it. 
This phenomenon is known as the 
magnetic effect of electric current. 
The magnetic field disappears when 
the current stops flowing.
Be a scientist 
You have just now made the same discovery which 
was made by the scientist Hans Christian Oersted 
(1777–1851) in 1820, that is, the discovery that 
electricity and magnetism are linked. He was a 
professor at a university in Denmark. It is said that 
once while giving a demonstration, he noticed that 
whenever an electrical circuit was closed or 
opened, the needle of a magnetic compass, lying 
nearby, deflected. He investigated this and when he was certain that 
an electric current indeed produced a magnetic field, he published 
his findings. This led to other scientists repeating his experiment to 
check if they got the same results, and further investigating the 
connection between electricity and magnetism. 
We have learnt about magnets 
and electric current in earlier 
grades. I used to think that there 
was no link between the two. But 
now we found that electricity 
and magnetic effect are linked!
Chapter 4.indd   48 Chapter 4.indd   48 6/28/2025   3:49:38 PM 6/28/2025   3:49:38 PM
Page 4


46
Curiosity — Textbook of Science for Grade 8
Electricity: Magnetic 
and Heating Effects
4
 z If we don’t have an electric lamp while making an electric circuit 
with an electric cell, is there any other way through which we 
can find out if current is flowing in the circuit?
 z Is it possible to make temporary magnets? How can these 
be made?
 z We can generate heat by burning fossil fuels and wood; but how 
is heat generated in various electrical appliances?
 z How do we know if a cell or a battery is dead? Can all 
cells and batteries be recharged?
 z Share your questions  
  ?
Probe and ponder
Chapter 4.indd   46 Chapter 4.indd   46 6/28/2025   3:49:31 PM 6/28/2025   3:49:31 PM
Chapter 4?—?Electricity: Magnetic and Heating Effects
47
It was the day of the science exhibition, and the school was 
buzzing with energy. Mohini and Aakarsh, along with their 
friends, went from one exhibit to another, eagerly exploring 
different models, asking questions and taking notes. One simple 
model really fascinated them. It was a working model of a lifting 
electromagnet which was displayed by their senior, Sumana. 
In it, instead of a hook like a typical crane, there was an iron 
nail wrapped with a wire, which was connected to a battery. 
When Sumana closed the circuit, the nail picked up iron paper 
clips like a magnet. When she opened the circuit, the clips fell 
off. Mohini and Aakarsh, were surprised. They remembered 
learning earlier (in the chapter ‘Exploring Magnets’, Curiosity, 
Grade 6) that magnetic materials were attracted by magnet and 
that iron was a magnetic material. But in Sumana’s model, there 
was no magnet, only an electric circuit. They were so excited that 
they wanted to try it out themselves.
4.1  Does an Electric Current Have a Magnetic 
Effect? 
Activity 4.1: Let us investigate
 z Collect a magnetic compass, an electric cell, a cell holder, 
two drawing pins, a safety pin, two nails, two pieces of 
connecting wires (one longer and one shorter), and two 
small pieces of cardboard. 
 z Using two drawing pins, a safety pin, and a cardboard 
piece, make a switch (as you made it earlier in the 
chapter ‘Electricity: Circuits and their Components’ in 
Curiosity, Grade 7).
 z Place the cell in the cell holder. 
 z Fix two nails to a piece of cardboard as shown in 
Fig. 4.1a. Fix the middle portion of the longer wire 
stretched between the nails, such that it is slightly above 
the surface of the cardboard. Attach one end of that 
wire to the cell holder and another end to the switch.
 z Connect the second wire between the cell holder and 
the switch.
 z Place the magnetic compass beneath the wire between 
the two nails (Fig. 4.1a). 
Fig. 4.1: An electric circuit 
and a magnetic compass
(b)
(a)
Chapter 4.indd   47 Chapter 4.indd   47 6/28/2025   3:49:32 PM 6/28/2025   3:49:32 PM
48
Curiosity — Textbook of Science for Grade 8
While watching the compass needle, move the switch to 
‘ON’ position to allow electric current to flow through the wire 
(Fig. 4.1b). What do you observe? 
 z Now again while watching the compass needle, move the 
switch to ‘OFF’ position. What do you observe this time? 
 z Move the switch between ‘ON’ and ‘OFF’ positions a few more 
times. Carefully observe how the compass needle behaves 
the each time.
You may have noticed that when the current flows, the compass 
needle gets deflected from its original direction. When the current 
stops, the needle returns to its original direction. 
As we have learnt earlier (in the chapter ‘Exploring Magnets’ 
in Curiosity, Grade 6), the compass needle is a tiny magnet which 
deflects when a magnet is brought near it and this magnetic effect 
can act through any non-magnetic materials kept in between. 
But why does the compass needle deflect when the current 
flows through the wire? The deflection indicates that the current 
carrying wire has a magnetic effect on the compass needle. 
When the current stops, this magnetic effect disappears and 
the compass needle returns to its original direction. The region 
around a magnet or a current carrying wire where its magnetic 
effect can be felt, such as by the deflection of a compass needle, 
is said to have a magnetic field.
When electric current flows 
through a conductor (like a wire), it 
produces a magnetic field around it. 
This phenomenon is known as the 
magnetic effect of electric current. 
The magnetic field disappears when 
the current stops flowing.
Be a scientist 
You have just now made the same discovery which 
was made by the scientist Hans Christian Oersted 
(1777–1851) in 1820, that is, the discovery that 
electricity and magnetism are linked. He was a 
professor at a university in Denmark. It is said that 
once while giving a demonstration, he noticed that 
whenever an electrical circuit was closed or 
opened, the needle of a magnetic compass, lying 
nearby, deflected. He investigated this and when he was certain that 
an electric current indeed produced a magnetic field, he published 
his findings. This led to other scientists repeating his experiment to 
check if they got the same results, and further investigating the 
connection between electricity and magnetism. 
We have learnt about magnets 
and electric current in earlier 
grades. I used to think that there 
was no link between the two. But 
now we found that electricity 
and magnetic effect are linked!
Chapter 4.indd   48 Chapter 4.indd   48 6/28/2025   3:49:38 PM 6/28/2025   3:49:38 PM
Chapter 4?—?Electricity: Magnetic and Heating Effects
49
The magnetic effect of electric current 
has many practical applications, such as 
in devices like electromagnets, electric 
bells, motors, fans, loudspeakers, 
and more. 
4.1.1 Electromagnets
Activity 4.2: Let us explore
 z Take around 50 cm long length of a flexible 
insulated wire, an iron nail, an electric cell, and 
few iron paper clips.
 z Tightly wrap the wire around the nail in the form 
of a coil, as shown in Fig. 4.2, and secure it with 
an adhesive tape.
 z Connect the ends of the wire to the cell. Take care 
to not connect the wires to the cell for more than 
a few seconds; otherwise, the cell may weaken 
quickly. 
 z Bring the nail close to the iron paper clips and 
lift up. Do the clips hang to the ends of the nail?
 z Disconnect the wire from the cell to stop the 
flow of electric current in the wire. Do the clips 
fall down?
When electric current flows through the coil, the clips cling 
to it. But when the current is stopped, the clips no longer cling 
to it. Let us now try to investigate these observations in detail 
through Activity 4.3.
Activity 4.3: Let us experiment
 z Take around 100 cm long flexible insulated wire, a piece 
of chart paper, an iron nail, an electric cell, two magnetic 
compasses, and few iron/steel paper clips.
 z Roll a piece of chart paper to make a cylinder of diameter 
roughly equal to the width of a pencil. Secure it with an 
adhesive tape.
 z Tightly wind around 50 turns of the insulated wire on the 
cylinder to form a cylindrical coil as shown in Fig. 4.3a. 
Secure the wire with an adhesive tape.
Fig. 4.3: (a) A coil 
of insulated wire
Can we use electric 
current to make a 
magnet?
Fig. 4.2: Coil of wire 
connected with a cell
Chapter 4.indd   49 Chapter 4.indd   49 6/28/2025   3:49:43 PM 6/28/2025   3:49:43 PM
Page 5


46
Curiosity — Textbook of Science for Grade 8
Electricity: Magnetic 
and Heating Effects
4
 z If we don’t have an electric lamp while making an electric circuit 
with an electric cell, is there any other way through which we 
can find out if current is flowing in the circuit?
 z Is it possible to make temporary magnets? How can these 
be made?
 z We can generate heat by burning fossil fuels and wood; but how 
is heat generated in various electrical appliances?
 z How do we know if a cell or a battery is dead? Can all 
cells and batteries be recharged?
 z Share your questions  
  ?
Probe and ponder
Chapter 4.indd   46 Chapter 4.indd   46 6/28/2025   3:49:31 PM 6/28/2025   3:49:31 PM
Chapter 4?—?Electricity: Magnetic and Heating Effects
47
It was the day of the science exhibition, and the school was 
buzzing with energy. Mohini and Aakarsh, along with their 
friends, went from one exhibit to another, eagerly exploring 
different models, asking questions and taking notes. One simple 
model really fascinated them. It was a working model of a lifting 
electromagnet which was displayed by their senior, Sumana. 
In it, instead of a hook like a typical crane, there was an iron 
nail wrapped with a wire, which was connected to a battery. 
When Sumana closed the circuit, the nail picked up iron paper 
clips like a magnet. When she opened the circuit, the clips fell 
off. Mohini and Aakarsh, were surprised. They remembered 
learning earlier (in the chapter ‘Exploring Magnets’, Curiosity, 
Grade 6) that magnetic materials were attracted by magnet and 
that iron was a magnetic material. But in Sumana’s model, there 
was no magnet, only an electric circuit. They were so excited that 
they wanted to try it out themselves.
4.1  Does an Electric Current Have a Magnetic 
Effect? 
Activity 4.1: Let us investigate
 z Collect a magnetic compass, an electric cell, a cell holder, 
two drawing pins, a safety pin, two nails, two pieces of 
connecting wires (one longer and one shorter), and two 
small pieces of cardboard. 
 z Using two drawing pins, a safety pin, and a cardboard 
piece, make a switch (as you made it earlier in the 
chapter ‘Electricity: Circuits and their Components’ in 
Curiosity, Grade 7).
 z Place the cell in the cell holder. 
 z Fix two nails to a piece of cardboard as shown in 
Fig. 4.1a. Fix the middle portion of the longer wire 
stretched between the nails, such that it is slightly above 
the surface of the cardboard. Attach one end of that 
wire to the cell holder and another end to the switch.
 z Connect the second wire between the cell holder and 
the switch.
 z Place the magnetic compass beneath the wire between 
the two nails (Fig. 4.1a). 
Fig. 4.1: An electric circuit 
and a magnetic compass
(b)
(a)
Chapter 4.indd   47 Chapter 4.indd   47 6/28/2025   3:49:32 PM 6/28/2025   3:49:32 PM
48
Curiosity — Textbook of Science for Grade 8
While watching the compass needle, move the switch to 
‘ON’ position to allow electric current to flow through the wire 
(Fig. 4.1b). What do you observe? 
 z Now again while watching the compass needle, move the 
switch to ‘OFF’ position. What do you observe this time? 
 z Move the switch between ‘ON’ and ‘OFF’ positions a few more 
times. Carefully observe how the compass needle behaves 
the each time.
You may have noticed that when the current flows, the compass 
needle gets deflected from its original direction. When the current 
stops, the needle returns to its original direction. 
As we have learnt earlier (in the chapter ‘Exploring Magnets’ 
in Curiosity, Grade 6), the compass needle is a tiny magnet which 
deflects when a magnet is brought near it and this magnetic effect 
can act through any non-magnetic materials kept in between. 
But why does the compass needle deflect when the current 
flows through the wire? The deflection indicates that the current 
carrying wire has a magnetic effect on the compass needle. 
When the current stops, this magnetic effect disappears and 
the compass needle returns to its original direction. The region 
around a magnet or a current carrying wire where its magnetic 
effect can be felt, such as by the deflection of a compass needle, 
is said to have a magnetic field.
When electric current flows 
through a conductor (like a wire), it 
produces a magnetic field around it. 
This phenomenon is known as the 
magnetic effect of electric current. 
The magnetic field disappears when 
the current stops flowing.
Be a scientist 
You have just now made the same discovery which 
was made by the scientist Hans Christian Oersted 
(1777–1851) in 1820, that is, the discovery that 
electricity and magnetism are linked. He was a 
professor at a university in Denmark. It is said that 
once while giving a demonstration, he noticed that 
whenever an electrical circuit was closed or 
opened, the needle of a magnetic compass, lying 
nearby, deflected. He investigated this and when he was certain that 
an electric current indeed produced a magnetic field, he published 
his findings. This led to other scientists repeating his experiment to 
check if they got the same results, and further investigating the 
connection between electricity and magnetism. 
We have learnt about magnets 
and electric current in earlier 
grades. I used to think that there 
was no link between the two. But 
now we found that electricity 
and magnetic effect are linked!
Chapter 4.indd   48 Chapter 4.indd   48 6/28/2025   3:49:38 PM 6/28/2025   3:49:38 PM
Chapter 4?—?Electricity: Magnetic and Heating Effects
49
The magnetic effect of electric current 
has many practical applications, such as 
in devices like electromagnets, electric 
bells, motors, fans, loudspeakers, 
and more. 
4.1.1 Electromagnets
Activity 4.2: Let us explore
 z Take around 50 cm long length of a flexible 
insulated wire, an iron nail, an electric cell, and 
few iron paper clips.
 z Tightly wrap the wire around the nail in the form 
of a coil, as shown in Fig. 4.2, and secure it with 
an adhesive tape.
 z Connect the ends of the wire to the cell. Take care 
to not connect the wires to the cell for more than 
a few seconds; otherwise, the cell may weaken 
quickly. 
 z Bring the nail close to the iron paper clips and 
lift up. Do the clips hang to the ends of the nail?
 z Disconnect the wire from the cell to stop the 
flow of electric current in the wire. Do the clips 
fall down?
When electric current flows through the coil, the clips cling 
to it. But when the current is stopped, the clips no longer cling 
to it. Let us now try to investigate these observations in detail 
through Activity 4.3.
Activity 4.3: Let us experiment
 z Take around 100 cm long flexible insulated wire, a piece 
of chart paper, an iron nail, an electric cell, two magnetic 
compasses, and few iron/steel paper clips.
 z Roll a piece of chart paper to make a cylinder of diameter 
roughly equal to the width of a pencil. Secure it with an 
adhesive tape.
 z Tightly wind around 50 turns of the insulated wire on the 
cylinder to form a cylindrical coil as shown in Fig. 4.3a. 
Secure the wire with an adhesive tape.
Fig. 4.3: (a) A coil 
of insulated wire
Can we use electric 
current to make a 
magnet?
Fig. 4.2: Coil of wire 
connected with a cell
Chapter 4.indd   49 Chapter 4.indd   49 6/28/2025   3:49:43 PM 6/28/2025   3:49:43 PM
50
Curiosity — Textbook of Science for Grade 8
Fig. 4.3: (b) Coil and magnetic compasses; 
(c) Coil connected to a cell; (d) Coil with 
iron nail inserted; (e) Coil with iron nail 
and clips
(d)
(e)
(c)
(b)
 z Place the compasses near the two ends of the 
cylindrical coil (Fig. 4.3b).
 z Connect the two ends of the coil with the 
terminals of the cell as shown in Fig. 4.3c and 
observe the magnetic compasses. Do you find 
any deflection in the needles of the compasses?
 z Disconnect the wire from the cell. Do the needles 
of the compasses come back to their original 
positions?
 z Insert an iron nail in the paper cylinder (Fig. 4.3d) 
and repeat the steps. Is there any difference in 
the deflection of the compass needles?
 z Place some iron paper clips near the two ends 
of the nail. Are the clips attracted to the ends of 
the nail?
It is observed that when current is passed through 
the cylindrical coil, it behaves like a magnet and 
deflects the needle of a magnetic compass. When an 
iron nail is inserted in the core of the coil, then the 
coil becomes a stronger magnet and the deflection of 
the magnetic compass needle is much more. It also 
attracts iron clips (Fig. 4.3e). When the current is 
stopped, the cylindrical coil loses its magnetic effect. 
A current carrying coil that behaves as a magnet is 
called an electromagnet. For practical applications, 
most electromagnets have an iron core to make them 
stronger.
Does electromagnet also have 
two poles like a bar magnet?
Activity 4.4: Let us investigate
 z Take the electromagnet made in Activity 4.3 and a magnetic 
compass. Label the two ends of the coil as A and B.
 z Place the magnetic compass near the end A of the coil as 
shown in Fig. 4.4a.
 z Connect the coil to the cell and observe the compass. Note down 
which pole of the magnetic compass is attracted to end A.
Chapter 4.indd   50 Chapter 4.indd   50 6/28/2025   3:49:47 PM 6/28/2025   3:49:47 PM
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FAQs on NCERT Textbook: Electricity: Magnetic and Heating Effects - Science Curiosity Class 8 - New NCERT

1. What are the main effects of electricity in terms of magnetism and heating?
Ans. Electricity has two significant effects: the magnetic effect and the heating effect. The magnetic effect occurs when an electric current passes through a conductor, producing a magnetic field around it. This principle is utilized in devices like electromagnets and electric motors. The heating effect, also known as Joule heating, happens when electric current flows through a resistance, causing the conductor to heat up. This principle is used in devices such as electric heaters and toasters.
2. How does an electromagnet work, and what are its applications?
Ans. An electromagnet works by passing an electric current through a coil of wire, creating a magnetic field. The strength of the electromagnet can be increased by adding more turns to the coil or increasing the current. Electromagnets are widely used in various applications, including electric bells, relays, magnetic cranes for lifting heavy metal objects, and in devices such as MRI machines in medical imaging.
3. What is the relationship between electric current and heat generated in a conductor?
Ans. The relationship between electric current and heat generation in a conductor is described by Joule's law, which states that the heat produced (H) is directly proportional to the square of the current (I) flowing through the conductor and the resistance (R) of the conductor. This can be expressed as H = I²R. Therefore, as the current increases, the heat generated also increases, which is why care must be taken to prevent overheating in electrical circuits.
4. What precautions should be taken to avoid overheating in electrical devices?
Ans. To avoid overheating in electrical devices, several precautions can be taken. These include using wires with appropriate thickness to handle the current, ensuring good insulation to prevent short circuits, using circuit breakers or fuses to cut off the current in case of overload, and not overloading electrical outlets. Regular maintenance and inspection of electrical devices can also help prevent overheating and ensure safety.
5. How do the heating and magnetic effects of electricity contribute to modern technology?
Ans. The heating and magnetic effects of electricity are fundamental to many modern technologies. The heating effect is utilized in various household appliances like ovens, heaters, and soldering tools, enhancing cooking and manufacturing processes. The magnetic effect is crucial in technologies such as electric motors, generators, and magnetic storage devices like hard drives. Together, these effects enable the functioning of numerous devices and systems essential for daily life, industry, and communication.
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