Section A – Multiple Choice
Questions (1 Mark Each)
1. Who
discovered that an electric current has a magnetic effect?
(a)
Alessandro Volta (b) Hans Christian
Oersted (c) Luigi Galvani (d) Michael Faraday
Answer:
(b) Hans Christian Oersted
2. A
magnetic compass placed near a current-carrying wire shows:
(a) No
change (b) Deflection of the
needle (c) The needle stops
working (d) The needle heats up
Answer:
(b) Deflection of the needle
3. The
region around a magnet or current-carrying wire where its magnetic effect can
be felt is called:
(a) Electric
field (b) Magnetic field (c) Force field (d) Current field
Answer:
(b) Magnetic field
4. When
the current in a wire is switched off, the magnetic field around it:
(a)
Increases (b) Reverses direction (c) Disappears (d) Stays the same
Answer:
(c) Disappears
5. A
current-carrying coil that behaves like a magnet is called:
(a) A dry
cell (b) An electromagnet (c) A Voltaic cell (d) A rheostat
Answer:
(b) An electromagnet
6.
Inserting an iron nail inside a current-carrying coil:
(a) Weakens
the magnetic effect (b) Has no effect
on the magnetic effect (c) Strengthens
the
magnetic
effect (d) Stops the current
Answer:
(c) Strengthens the magnetic effect
7. The
strength of an electromagnet can be increased by:
(a)
Decreasing the number of turns (b)
Decreasing the current (c) Increasing
the number of turns of the coil (d)
Removing the iron core
Answer:
(c) Increasing the number of turns of the coil
8. The
polarity of an electromagnet can be reversed by:
(a)
Increasing the number of cells (b)
Reversing the direction of current (c)
Adding more turns (d) Removing the
core
Answer:
(b) Reversing the direction of current
9.
Lifting electromagnets are widely used in:
(a)
Hospitals (b) Scrap yards and
factories (c) Kitchens (d) Classrooms
Answer:
(b) Scrap yards and factories
10. A
lifting electromagnet releases the objects it is holding when:
(a) More
current is supplied (b) The current is
switched off (c) The iron core is
removed (d) The compass is removed
Answer:
(b) The current is switched off
11. Which
of these is NOT an application of the magnetic effect of electric current?
(a) Electric
bell (b) Electric motor (c) Loudspeaker (d) Electric kettle
Answer:
(d) Electric kettle
12. A
nichrome wire has ______ resistance compared to a copper wire of the same size
and length.
(a)
Lower (b) Zero (c) Higher (d) Equal
Answer:
(c) Higher
13. The
heating effect of electric current occurs because:
(a) Current
has no effect on conductors (b) The
conductor offers resistance to current flow
(c) The wire becomes magnetic
(d) The wire loses electrons permanently
Answer:
(b) The conductor offers resistance to current flow
14. The
coil or rod used in a heating appliance is called:
(a) A
filament core (b) A heating
element (c) An electromagnet (d) An electrode
Answer:
(b) A heating element
15. Which
of the following works on the heating effect of electric current?
(a) Electric
bell (b) Electric motor (c) Electric iron (d) Magnetic compass
Answer:
(c) Electric iron
16. For
the same duration, a battery with more cells produces:
(a) Less
heat in a wire (b) The same heat as
one cell (c) More heat in a wire (d) No heat at all
Answer:
(c) More heat in a wire
17. The
heat generated in a wire depends on all of the following EXCEPT:
(a) Material
of the wire (b) Length of the
wire (c) Colour of the wire (d) Duration of current flow
Answer:
(c) Colour of the wire
18.
Overheating of electrical appliances can lead to:
(a) Cooling
of wires (b) Melting of plastic parts
and fires (c) Stronger magnetic
fields (d) Better conductivity
Answer:
(b) Melting of plastic parts and fires
19. In a
Voltaic cell, the liquid used to produce a chemical reaction with the
electrodes is called:
(a)
Conductor (b) Electrolyte (c) Insulator (d) Filament
Answer:
(b) Electrolyte
20. In a
Voltaic cell, electric current flows in the external circuit from the:
(a) Negative
terminal to positive terminal (b)
Positive terminal to negative terminal
(c) Electrolyte to the electrode
(d) Electrode to the electrolyte directly
Answer:
(b) Positive terminal to negative terminal
21. A
Voltaic cell is also known as a:
(a) Dry
cell (b) Galvanic cell (c) Rechargeable battery (d) Lithium cell
Answer:
(b) Galvanic cell
22. A
cell is said to be 'dead' when:
(a) It has
too much charge (b) The chemicals
inside get used up (c) It becomes
magnetic (d) The electrolyte becomes
solid
Answer:
(b) The chemicals inside get used up
23. Luigi
Galvani observed that a dead frog's leg kicked because:
(a) The frog
was alive (b) He believed electricity
came from the frog (c) He believed
electricity came from the metals (d)
The leg was heated
Answer:
(b) He believed electricity came from the frog
24.
Alessandro Volta proved that electric current was produced by:
(a) The
frog's leg alone (b) The combination
of metals and liquid (c) Only one type
of metal (d) Heat alone
Answer:
(b) The combination of metals and liquid
25. In a
lemon cell, the lemon juice acts as the:
(a)
Electrode (b) Electrolyte (c) Insulator (d) Heating element
Answer:
(b) Electrolyte
26. In a
dry cell, the electrolyte is:
(a) A
liquid (b) Absent (c) A thick moist paste (d) A gas
Answer:
(c) A thick moist paste
27. In a
dry cell, the negative terminal is the:
(a) Carbon
rod (b) Metal cap (c) Zinc container (d) Glass container
Answer:
(c) Zinc container
28. A dry
cell is a ______ cell.
(a)
Rechargeable (b) Single use (c) Solid-state (d) Reversible
Answer:
(b) Single use
29.
Rechargeable batteries are commonly used in:
(a) Mobile
phones and laptops (b) Voltaic frog
experiments (c) Magnetic compasses
only (d) Dry cardboard cylinders
Answer:
(a) Mobile phones and laptops
30.
Lithium-ion batteries are a common type of:
(a)
Non-rechargeable dry cell (b)
Rechargeable battery (c) Voltaic cell
using lemons (d)
Electromagnet
Answer:
(b) Rechargeable battery
Section B – Short Answer Questions
(2 Marks Each)
1. What
do you observe when a magnetic compass is placed near a current-carrying wire?
Answer: The
compass needle gets deflected from its original direction when current flows
through the wire. When the current is stopped, the needle returns to its
original direction.
2. Define
magnetic effect of electric current.
Answer: When
electric current flows through a conductor, it produces a magnetic field around
it. This is known as the magnetic effect of electric current.
3. What
is a magnetic field?
Answer: The
region around a magnet or a current-carrying wire where its magnetic effect can
be felt (for example, by the deflection of a compass needle) is called a
magnetic field.
4. Define
an electromagnet.
Answer: 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.
5. Name
two factors on which the strength of an electromagnet depends.
Answer: The
strength of an electromagnet depends on the amount of electric current flowing
through the coil and the number of turns of the coil.
6. How
can the poles of an electromagnet be reversed?
Answer: The
poles of an electromagnet can be reversed by reversing the direction of the
current flowing through the coil.
7. Give
two practical applications of the magnetic effect of electric current.
Answer: Two
applications are: (i) electric bell, and (ii) lifting electromagnets used in
factories and scrap yards (electric motors and loudspeakers are also valid
answers).
8. What
is a lifting electromagnet used for?
Answer: A
lifting electromagnet is used to lift, move, and sort heavy iron/steel objects.
When switched ON it lifts the object, and when switched OFF the magnetic field
disappears and the object is released.
9. Why
does a nichrome wire get warm when current flows through it?
Answer: A
nichrome wire offers high resistance to the flow of current. This resistance
causes some of the electrical energy to be converted into heat energy, so the
wire gets warm.
10.
Define the heating effect of electric current.
Answer: When
an electric current passes through a conductor, it gets heated due to the
resistance offered by the conductor to the flow of current. This is called the
heating effect of electric current.
11. Name
any three household appliances that work on the heating effect of electric
current.
Answer: Any
three of: electric iron, electric kettle, electric room heater, electric stove,
water heating immersion rod, hair dryer.
12. What
is a heating element?
Answer: A
heating element is a rod or coil of wire (usually nichrome) inside an
electrical appliance that produces heat when current flows through it.
13. Name
two factors on which the heat generated in a wire depends.
Answer: The
heat generated in a wire depends on the material of the wire, its thickness,
its length, and the duration for which the current flows (any two).
14. Why
is nichrome preferred over copper for making heating elements?
Answer:
Nichrome is preferred because it has a much higher resistance than copper of
the same size and length, so it converts more electrical energy into heat,
making it ideal for heating elements.
15. What
is an electrolyte? Give one example.
Answer: An
electrolyte is a liquid or paste that undergoes a chemical reaction with the
electrodes to produce electricity. Example: the weak acid/salt solution in a
Voltaic cell, or lemon juice in a lemon cell.
16. Who
discovered the link between electricity and magnetism, and in which year?
Answer: Hans
Christian Oersted discovered the link between electricity and magnetism in
1820.
17. What
happens to a Voltaic cell when its chemicals get used up?
Answer: When
the chemicals inside a Voltaic cell get used up, the cell stops producing
electricity. It is then called 'dead' and cannot supply any more electricity.
18. Why
is a dry cell called 'dry'?
Answer: A
dry cell is called 'dry' because its electrolyte is not a liquid but a thick
moist paste.
19. Name
the positive and negative terminals of a dry cell.
Answer: In a
dry cell, the carbon rod (covered with a metal cap) acts as the positive
terminal, and the zinc container acts as the negative terminal.
20. What
is the main advantage of a rechargeable battery over a dry cell?
Answer: A
rechargeable battery can be recharged and reused multiple times, which prevents
wastage and saves money over time, unlike a dry cell which is a single-use cell
that must be disposed of once used up.
Section C – Three Mark Questions
1.
Describe Activity 4.1 to show that an electric current has a magnetic effect.
What do you observe when the switch is moved from OFF to ON?
Answer: In
Activity 4.1, a circuit is set up with a cell, a switch, and a wire stretched
between two nails, with a magnetic compass placed beneath the wire. When the
switch is moved to ON, current flows through the wire and the compass needle
gets deflected from its original direction. When the switch is moved to OFF,
the current stops and the needle returns to its original position. This shows that
a current-carrying wire has a magnetic effect, which disappears when the
current stops.
2.
Explain, with the help of an example, how a current-carrying coil
(electromagnet) can pick up iron paper clips. What happens when the current is
switched off?
Answer: When
a wire is wound into a coil around an iron nail and connected to a cell,
current flowing through the coil makes it behave like a magnet, and it can
attract and lift iron paper clips placed near its ends. This happens because
the current-carrying coil produces a magnetic field, and the iron nail strengthens
this field. When the wire is disconnected from the cell, the current stops, the
magnetic field disappears, and the clips fall off.
3.
Explain how you would find out the polarity of the two ends of an electromagnet
using a magnetic compass.
Answer:
Place a magnetic compass near one end (say end A) of the electromagnet and
connect the coil to the cell. Note which pole (N or S) of the compass needle is
attracted to end A; since unlike poles attract, if the north pole of the
compass is attracted to end A, then end A is a south pole. Repeat this near end
B; its polarity will be opposite to that of end A, confirming that an
electromagnet has two poles like a bar magnet.
4.
Describe the contribution of Hans Christian Oersted to our understanding of
electricity and magnetism.
Answer: Hans
Christian Oersted, a professor at a university in Denmark, discovered in 1820
that electricity and magnetism are linked. While giving a demonstration, he
noticed that whenever an electric circuit was closed or opened, a nearby
magnetic compass needle deflected. He investigated this further and, once
certain that an electric current produced a magnetic field, published his findings,
leading other scientists to repeat and confirm the discovery.
5.
Explain why an electromagnet with an iron core is stronger than one without a
core.
Answer: An
iron nail is a magnetic material, so when it is placed inside a
current-carrying coil, it gets magnetised and adds to the magnetic field
produced by the coil itself. This combined magnetic field is much stronger than
that of the coil alone, causing greater deflection of a compass needle and allowing
the electromagnet to attract more iron paper clips than a coil without a core.
6.
Describe how a nichrome wire connected to a cell demonstrates the heating
effect of electric current.
Answer: In
this activity, a nichrome wire is connected between two nails on a cardboard
with a cell and switch in the circuit. When the switch is OFF, the wire feels
normal, but when the switch is moved to ON for about 30 seconds and then OFF,
the wire feels noticeably warm when touched momentarily. This happens because
nichrome offers high resistance to current flow, and this resistance converts
electrical energy into heat energy, demonstrating the heating effect of
electric current.
7.
Explain why overheating of electrical appliances can be dangerous. Suggest one
precaution to avoid this.
Answer:
Overheating in appliances can damage plugs and sockets, melt plastic parts, and
even cause fires, since excess heat is generated when current flow is not
properly regulated. One precaution is to use wires, plugs, and sockets that are
correctly rated for the electric current of the connections, and to include
safety devices in household circuits to cut off current if it becomes too high.
8.
Describe the construction and working of a Voltaic cell with a labelled
diagram.
Answer: A
Voltaic (or Galvanic) cell consists of two electrodes made of different metals
dipped in an electrolyte (a weak acid or salt solution), contained in a glass
or plastic vessel. A chemical reaction
between the
electrodes and the electrolyte produces electricity; when the circuit is
connected, current flows from the positive terminal through the external
circuit to the negative terminal. Over time the chemicals get used up and the
cell becomes 'dead', after which it can no longer supply electricity.
9.
Explain how a simple electric cell can be made using lemons. What acts as the
electrolyte and what act as the electrodes?
Answer:
Copper wire and an iron nail are inserted into a lemon, kept slightly apart,
acting as the two electrodes; this is repeated for several lemons, which are
then connected in series using connecting wires, with an LED connected across
the two free ends. The lemon juice acts as the electrolyte, allowing a chemical
reaction between the copper and iron electrodes that generates electricity, causing
the LED to glow (with correct polarity of connection).
10.
Compare a dry cell and a rechargeable battery in terms of use and lifespan.
Answer: A
dry cell is a single-use cell with a paste-like electrolyte; once its chemicals
are used up, it must be disposed of and cannot be reused. A rechargeable
battery, on the other hand, can be charged and reused many times, which reduces
wastage and saves money over time, though it too eventually wears out after
repeated charging and use. Rechargeable batteries are used in devices like
phones, laptops, and vehicles, while dry cells are used in simple low-power
devices.
Section D – Long Answer Questions (5
Marks Each)
1. With
the help of Activity 4.3, explain how you would show that a current-carrying
coil behaves like a magnet. Describe the role of the iron nail and the effect
of increasing the number of cells or turns of the coil.
Answer: In
Activity 4.3, a cylindrical coil is made by winding about 50 turns of insulated
wire on a paper cylinder, with magnetic compasses placed near its two ends.
When the coil is connected to a cell, both compass needles deflect, showing
that the current-carrying coil behaves like a magnet; disconnecting the cell
makes the needles return to normal. When an iron nail is inserted into the
coil's core and the steps are repeated, the deflection of the compass needles
is much greater, and the coil can now attract iron paper clips – showing that
an iron core makes the electromagnet stronger.
Repeating
the activity with a battery of 2 and then 4 cells (keeping the coil the same)
shows greater deflection and stronger attraction with more cells, since a
larger current produces a stronger magnetic field. Similarly, using 2 cells
with a coil having more turns also increases the strength of the electromagnet.
Thus, the strength of an electromagnet depends on the current flowing through
the coil, the number of turns of the coil, and the presence of an iron core.
2. What
is an electromagnet? Explain, with examples, at least four devices that use
electromagnets or the magnetic effect of electric current in daily life.
Answer: An
electromagnet is a current-carrying coil (usually with an iron core) that
behaves as a magnet only while current flows through it, and loses its
magnetism when the current stops. Devices that use the magnetic effect of
electric current include:
(i) Lifting
electromagnets, used in factories and scrap yards to lift, move, and sort heavy
iron/steel objects by switching current ON and OFF;
(ii)Electric
bells, which use an electromagnet to attract a metal striker that rings the
bell;
(iii)
Electric motors, which use the magnetic effect to convert electrical energy
into rotational motion; and
(iv) Loudspeakers,
which use electromagnets to convert electrical signals into sound vibrations.
In each case, the ability to control the magnetic effect by switching current
ON/OFF or varying it makes these devices useful.
3.
Explain the heating effect of electric current. Describe with a labelled
diagram how Activity 4.5 demonstrates this effect using a nichrome wire.
Answer: When
electric current flows through a conductor, it faces resistance, and this
resistance converts some electrical energy into heat energy, causing the
conductor to warm up; this is called the heating effect of electric current. In
Activity 4.5, a nichrome wire is tied between two nails on a cardboard,
connected to a cell through a switch, forming a circuit as shown in the figure
(cell – switch – nichrome wire, connected by wires). With the switch OFF, the
wire feels at room temperature; when the switch is turned ON for about 30
seconds and then OFF, touching the wire momentarily shows that it has become
distinctly warm. This happens because nichrome has a higher resistance than a conductor
like copper of the same size, so more electrical energy is converted to heat in
it. The activity confirms that passing current through a conductor with
resistance generates heat, and this effect increases with a larger current (as
observed when the experiment is repeated with 2 cells instead of 1).
4.
Describe five household appliances that work on the heating effect of electric
current and explain the common principle behind their working.
Answer: Five
household appliances that work on the heating effect of electric current are:
(i)
Electric
room heater,
(ii)
Electric
stove,
(iii)
Electric
kettle,
(iv)
Electric
iron, and
(v)
Water
heating immersion rod (a hair dryer is another example).
All these
appliances contain a rod or coil of wire called a heating element, usually made
of a high-resistance material like nichrome. When current flows through this
heating element, the resistance it offers converts electrical energy into heat
energy, which is then used for heating water, cooking, ironing clothes, or
warming a room. In some appliances, this heating element can even be seen
glowing red hot. The common underlying principle in all these appliances is
thus the heating effect of electric current, where resistance in the conductor generates
heat proportional to the current, the resistance of the material, and the
duration of current flow.
5.
Explain the working of a Voltaic cell with a neat, labelled diagram. Describe
the historical experiments of Galvani and Volta that led to its discovery.
Answer: A
Voltaic cell (also called a Galvanic cell) consists of two metal rods of
different materials, called electrodes, partly dipped in a liquid electrolyte
(usually a weak acid or salt solution) contained in a glass or plastic vessel.
A chemical reaction takes place between the electrodes and the electrolyte,
producing electricity; when connected in a circuit with a lamp, current flows
from the positive terminal through the circuit to the negative terminal. This
was discovered through the experiments of two Italian scientists: Luigi
Galvani, who in the late 1700s noticed that a dead frog's leg kicked when
touched with two different metals (copper and iron) and believed the
electricity came from the frog itself; and Alessandro Volta, who disagreed and
believed the electricity came from the combination of metals, not the frog.
Volta tested this by replacing the frog's leg with saltwater-soaked paper and
still obtained an electric current, proving that it was the combination of
metals and liquid electrolyte that generated the current – leading to the
invention of the first battery.
6.
Describe the internal structure of a dry cell with a labelled diagram,
mentioning its electrodes and electrolyte.
Answer: A
dry cell has a zinc container that acts as the negative terminal, and inside it
is a carbon rod at the centre, covered with a metal cap, that acts as the
positive terminal. The space between the carbon rod and the zinc container is
filled with a thick, paste-like electrolyte rather than a liquid, which is why
it is called a 'dry' cell. A chemical reaction between the zinc container, the
carbon rod, and the paste electrolyte produces electricity that can be tapped
from the metal cap (positive terminal) and the zinc container (negative
terminal). The dry cell is a single-use cell, meaning that once its chemicals
are used up, it stops working and must be disposed of, rather than being
recharged.
7.
Explain what rechargeable batteries are. Describe at least four devices in
which they are used and explain why they are preferred over single-use dry
cells.
Answer:
Rechargeable batteries are batteries that can be charged and reused multiple
times, unlike single-use dry cells which must be thrown away once used up; this
prevents wastage of materials and saves money over time. They are used in a
wide range of devices, including:
(i) laptops,
(ii) mobile phones, (iii) cameras, and (iv) inverters and electric vehicles,
which use bigger rechargeable batteries. Rechargeable batteries are preferred
over dry cells because they reduce the frequency of battery disposal, are more
economical in the long run for devices used regularly, and reduce electronic
waste. However, rechargeable batteries do not last forever either; after being
charged and used many times, they slowly wear out, which is why devices like
phones may need charging more often after a year or two of use.
8.
Explain how the strength and polarity of an electromagnet can be changed.
Describe an activity to demonstrate both effects.
Answer: The
strength of an electromagnet can be increased by increasing the electric
current flowing through the coil (for example, by using a battery with more
cells) or by increasing the number of turns of the coil; inserting an iron core
also makes it stronger. This can be demonstrated by repeating the coil activity
with 2 and then 4 cells while keeping the same coil, and observing greater compass
deflection and more paperclips attracted as the current increases; similarly,
using coils with more turns (e.g., 25, 50, 75, 100 turns) connected to the same
cell shows increasing deflection with more turns. The polarity of an
electromagnet can be reversed by reversing the direction of the current flowing
through the coil; this can be demonstrated by connecting the cell in the
opposite orientation and observing that the pole of the compass needle
attracted to a given end of the coil changes.
9.
Discuss the industrial and everyday applications of the heating effect of
electric current, along with the safety precautions needed to prevent
accidents.
Answer: The
heating effect of electric current has many everyday applications, such as
electric room heaters, stoves, kettles, irons, and immersion rods, all of which
use a heating element to convert electrical energy into heat. Industrially, it
is used in high-temperature furnaces in steel manufacturing, which use electric
current to melt and recycle scrap steel into usable steel. However, the heating
effect can also cause problems: energy is lost as heat in wires during
transmission, and overheating in appliances or wiring can damage plugs and
sockets (melting plastic parts) or even cause fires. To prevent such accidents,
household circuits should use wires, plugs, and sockets rated for the correct current,
and include safety devices designed to cut off current if it exceeds a safe
level, minimizing the risk of overheating and fire.
10.
Describe how scientists are working on improving batteries. Explain the
significance of lithium-ion and solid-state batteries for the future of
environmentally friendly electrical power.
Answer:
Scientists are continuously working to improve rechargeable batteries since the
most common type used today, the lithium-ion (Li-ion) battery, relies on metals
like lithium and cobalt that are mined and processed only in limited parts of
the world, leading countries to race to secure supplies, recycle old batteries,
and develop new technologies. The next major advance being developed is the
solid-state battery, which replaces the liquid or paste-like electrolyte with a
solid material; these are expected to be safer, charge faster, and last longer
than current batteries. Such improvements in rechargeable battery technology
are important because they support the development of environmentally friendly
sources of electrical power, reduce dependence on scarce raw materials, and
help minimise the environmental hazards posed by discarding used batteries containing
materials like acids, lead, cadmium, nickel, or lithium.
Section E – Assertion-Reason
Questions (1 Mark Each)
Each
question below consists of two statements – Assertion (A) and Reason (R).
Choose the correct option:
(a) Both A
and R are true and R is the correct explanation of A
(b) Both A
and R are true but R is NOT the correct explanation of A
(c) A is
true but R is false
(d) A is
false but R is true
1.
Assertion (A): A magnetic compass placed near a current-carrying wire gets
deflected.
Reason
(R): An electric current flowing through a conductor produces a magnetic field
around it.
Answer: (a).
Both statements are true, and R correctly explains A: the deflection happens
precisely because current flowing through the wire creates a magnetic field,
which acts on the compass needle.
2.
Assertion (A): An iron nail wrapped with a current-carrying coil can lift iron
paper clips.
Reason
(R): A current-carrying coil behaves like a magnet and this effect is called
the magnetic effect of electric current.
Answer: (a).
Both statements are true, and R correctly explains A: the coil's magnetic
behaviour (its magnetic effect) is exactly what allows it to attract and lift
the iron clips.
3.
Assertion (A): Inserting an iron core inside a current-carrying coil makes the
electromagnet weaker.
Reason
(R): Iron is a magnetic material and increases the magnetic field of the coil.
Answer: (d).
A is false: inserting an iron core makes the electromagnet stronger, not
weaker. R is true: iron is indeed a magnetic material that strengthens the
magnetic field of the coil.
4.
Assertion (A): The magnetic field around a current-carrying wire disappears as
soon as the current is switched off.
Reason
(R): The magnetic effect of electric current exists only while current flows
through the conductor.
Answer: (a).
Both statements are true, and R correctly explains A: the magnetic effect of
current exists only while current flows, so the field vanishes the instant the
current is switched off.
5.
Assertion (A): A nichrome wire heats up more than a copper wire of the same
length and thickness for the same current.
Reason
(R): Nichrome offers higher resistance to the flow of current than copper.
Answer: (a).
Both statements are true, and R correctly explains A: nichrome's higher
resistance compared to copper is exactly why it produces more heat for the same
current.
6.
Assertion (A): Electric kettles, irons, and room heaters all work on the same
underlying principle.
Reason
(R): All these appliances use a heating element based on the heating effect of
electric current.
Answer: (a).
Both statements are true, and R correctly explains A: kettles, irons, and
heaters all rely on a heating element based on the heating effect of electric
current, which is their shared underlying principle.
7.
Assertion (A): A single electric cell produces a weaker magnetic field in a
coil than a battery of two cells.
Reason
(R): A battery of more cells provides a larger current than a single cell.
Answer: (a).
Both statements are true, and R correctly explains A: a battery of more cells
supplies a larger current, which produces a stronger magnetic field and hence
more deflection.
8.
Assertion (A): A Voltaic cell can supply electricity forever without stopping.
Reason
(R): In a Voltaic cell, the chemical reaction between the electrodes and
electrolyte continues indefinitely without using up any material.
Answer: (d).
A is false: a Voltaic cell eventually becomes 'dead' once its chemicals are
used up. R is also false, since the chemical reaction does not continue
indefinitely – the reactants are gradually consumed.
9.
Assertion (A): A dry cell is called 'dry' because it contains no electrolyte at
all.
Reason
(R): The electrolyte in a dry cell is a thick moist paste rather than a liquid.
Answer: (d).
A is false: a dry cell does contain an electrolyte, just not a liquid one. R is
true: the electrolyte in a dry cell is a thick moist paste, which is why the
cell is called 'dry' rather than because it lacks an electrolyte altogether.
10.
Assertion (A): Rechargeable batteries are preferred in laptops and mobile
phones over single-use dry cells.
Reason
(R): Rechargeable batteries can be charged and reused multiple times, reducing
wastage and cost over time.
Answer: (a).
Both statements are true, and R correctly explains A: rechargeable batteries
are preferred precisely because they can be reused many times, reducing cost
and waste compared to single-use dry cells.
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