Why is learning about electricity important for the students in school?

In order to be thorough with the most important commodities in modern Sciences , one must understand electricity. A fundamental understanding of electricity is also necessary for many technical occupations in order to create the technologies and goods that we use in our every -day lives. For this purpose, Extramarks has curated this important questions Class 10 Science Chapter 12

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Nowadays, electricity is almost necessary for our daily work functioning. It is utilized for residential purposes such as operating fans, computer, electric stoves, air conditioning, and lighting up rooms. It is used in factories to operate heavy machines. Electricity is also used to produce various products, including food, clothing, and paper.

Home > CBSE > CBSE Important Questions Class 10 Science Chapter 12 – Magnetic Effects of Electric Current

CBSE Important Questions Class 10 Science Chapter 12 – Magnetic Effects of Electric Current

Class 10 Science Chapter 12 Magnetic Effects of Electric Current is part of the CBSE Class 10 Science syllabus. It explains that a current-carrying wire produces a magnetic field around it, how to find the direction of that field using the right-hand thumb rule and Maxwell's corkscrew rule, the field of a bar magnet and of a solenoid, the force on a current-carrying conductor in a magnetic field, Fleming's left-hand rule, electromagnetic induction, the electric motor and generator, and domestic electric circuits.

These CBSE important questions for Class 10 Science Chapter 12 cover why home appliances are connected in parallel, two ways of tracing the field lines of a bar magnet, how the field changes with current and distance, Maxwell's corkscrew rule and the solenoid, the deflection of a compass near a conductor, the principle of the electric generator, and what magnetic field lines tell us. Every question has a clear step-by-step answer in simple English with figures, so students can practise on their own, parents can check the answers, and teachers can use them for class tests.

Q1. Given below are two statements labelled as Assertion (A) and Reason (R).
Assertion (A): All the appliances in a domestic circuit are connected in parallel.
Reason (R): Current flows in a single channel in a series circuit whereas it flows in independent paths in a parallel circuit.
(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

Answer: (a) Both A and R are true, and R is the correct explanation of A.
Home appliances are connected in parallel so that each one gets the full supply voltage of 220 V and can be switched on or off on its own. If they were in series, all of them would share the voltage, none would work properly, and switching off one would stop them all. The independent paths of a parallel circuit are exactly the reason for this arrangement.

Q2. Name two methods by which the direction of the magnetic field lines of a bar magnet can be obtained.

Answer: 1. Iron filings method: Place a sheet of paper over a bar magnet and sprinkle iron filings on it. On tapping the paper gently, the filings line up along the field lines and show their pattern.
2. Magnetic compass method: Place a small compass at different points around the magnet and mark the direction in which its north pole points each time. Joining these marks traces the field lines and shows their direction, from the north pole to the south pole outside the magnet.

Q3. What will happen to the magnitude of the magnetic field if the amount of electric current flowing through the conductor is increased?

Answer: The magnetic field around the conductor will also become stronger.
The strength of the magnetic field at a point is directly proportional to the current flowing through the conductor. So if the current is doubled, the magnetic field at that point also becomes double. The field becomes weaker as we move farther away from the wire.

Q4. State Maxwell's corkscrew rule. How is it applied to a solenoid?

Answer: Maxwell's corkscrew rule: If a right-handed corkscrew is turned so that its tip advances in the direction of the current in a conductor, then the direction in which the handle turns gives the direction of the magnetic field lines around the conductor.
In a solenoid: The rule is applied to each turn of the coil. Taking the direction of the current in the turns, the rule shows that the field lines go round each turn and run through the inside of the solenoid in one direction. The field inside a solenoid is uniform and strong, and the solenoid behaves like a bar magnet, with the end from which the field lines come out acting as the north pole.

Q5. Read the statements and select the appropriate answer.
Assertion (A): When a magnetic compass is moved away from a current-carrying straight conductor, its deflection reduces gradually.
Reason (R): The magnetic field of the current-carrying straight conductor becomes stronger as we move away from the conductor.
(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 for A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Answer: (c) A is true, but R is false.
The deflection of the compass does become smaller as it is moved away, so A is true. But the reason given is wrong: the magnetic field becomes weaker, not stronger, as the distance from the conductor increases. That weaker field is what causes the smaller deflection.

Q6. Read the statements and select the appropriate answer.
Assertion (A): A magnetic needle deflects when placed near a current-carrying conductor.
Reason (R): A current-carrying conductor behaves like a magnet.
(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 for A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Answer: (b) Both A and R are true, but R is not the correct explanation for A.
Both statements are correct facts. However, the exact reason the needle deflects is that the current produces a magnetic field around the conductor, and the needle aligns itself with that field. Saying the conductor 'behaves like a magnet' is a true but more general statement, so it does not properly explain the assertion. This observation was first made by Oersted.

Q7. When a magnetic needle is brought near a current-carrying conductor, it deflects in a certain direction. As the direction of electric current is reversed in the circuit, the magnetic needle __________.
(a) comes to its initial position
(b) remains in the same position
(c) deflects in the opposite direction
(d) starts oscillating

Answer: (c) deflects in the opposite direction
The direction of the magnetic field depends on the direction of the current. When the current is reversed, the field around the conductor also reverses. The needle always lines up with the field, so it now turns the other way.

Q8. The electric generator works on the principle of
(a) magnetic field lines
(b) electromagnetic induction
(c) both (a) and (b)
(d) none of these

Answer: (b) electromagnetic induction
An electric generator works on the principle of electromagnetic induction, discovered by Michael Faraday. When a coil is rotated in a magnetic field, the magnetic field through the coil keeps changing, and this changing field induces an electric current in the coil.

Q9. The magnetic field at a point due to a current-carrying conductor is directly proportional to
A. current flowing through the conductor
B. distance of the conductor
C. resistance of the conductor
(a) A and C
(b) A and B
(c) B
(d) A

Answer: (d) A
The magnetic field is directly proportional only to the current. It is inversely proportional to the distance from the conductor, so B is wrong, and it does not depend directly on the resistance of the conductor, so C is wrong.

Q10. An electron beam is moving vertically upwards. If it passes through a magnetic field which is directed from south to north, it will be deflected towards the
(a) south
(b) north
(c) west
(d) east

Answer: (c) west
An electron moving upwards is the same as a conventional current moving downwards. Using Fleming's left-hand rule with the field pointing from south to north and the current pointing downwards, the force on the beam comes out towards the west, so the beam is deflected to the west.

Q11. Magnetic field lines determine
(a) only the direction of the magnetic field
(b) both the direction and the relative strength of the magnetic field
(c) only the relative strength of the magnetic field
(d) the shape of the magnetic field

Answer: (b) both the direction and the relative strength of the magnetic field
The direction of the field at a point is the direction of the tangent to the field line there. The closeness of the lines shows the strength: where the lines are crowded together the field is strong, and where they are far apart the field is weak.

Q12. Statement A: The line joining the earth's magnetic poles is called the magnetic axis.
Statement B: Chemical energy is converted into electrical energy in an AC generator.
(a) Statement A is true, B is false
(b) Both the statements A and B are true
(c) Neither statement A nor statement B is true
(d) Statement B is true, A is false

Answer: (a) Statement A is true, B is false.
Statement A is correct: the imaginary line joining the magnetic north and south poles of the Earth is called the magnetic axis.
Statement B is wrong: in an AC generator, mechanical energy (the energy of the rotating coil) is converted into electrical energy, not chemical energy. Chemical energy is converted into electrical energy in a cell or battery.

Related Study Material on Extramarks

Q.1 An object is placed in front of a convex lens at a distance of

$f± \frac{f}{n},$

where f is the magnitude of the focal length of the lens.
Prove that the magnification produced by the lens is n. Also find the two values of the object distances for which a convex lens of power 2.5 D will produce an image that is four times as large as the object.

Marks:5
Ans

$\begin{array}{l} Given: \\ Object distance, | u | = f \frac{f}{n}; \\ Focal length = f; \\ Image distance, v = \\ ByLens’Formula, \\ \frac{1}{f} = \frac{1}{v} \frac{1}{u} \\ Object distance is always negative. \\ \frac{1}{f} = \frac{1}{v} + \frac{1}{f \frac{f}{n}} \\ \frac{1}{v} = \frac{1}{f} \frac{1}{f \frac{f}{n}} \\ \frac{1}{v} = \frac{f \frac{f}{n} f}{f (f \frac{f}{n})} \\ \frac{1}{v} = \frac{\frac{1}{n}}{(f \frac{f}{n})} \\ v= \frac{(f \frac{f}{n})}{\frac{1}{n}} \\ Now, magnification, | m | = |\frac{v}{u}| \\ |m|=n \\ Hence, proved. \\ Now, u= (f \frac{f}{n}) \\ Butf = \frac{1}{2.5} m = 0.4 m (ˆµ f = \frac{1}{P}) \\ u = (0.4 \frac{0.4}{4}) (ˆµ n=4) \\ u= (0.4 0.1) \\ u = 0.5mor 0.3 m \end{array}$

Q.2 An object is placed at 10cm in front of a concave mirror of focal length 15cm. Find the position, nature and size of the image.

Marks:5
Ans

$\begin{array}{l} Given u = 10 cm; f = 15 cm; v =; m = \\ \frac{1}{v} + \frac{1}{u} = \frac{1}{f} \\ \frac{1}{v} + \frac{1}{10} = \frac{1}{15} \\ \frac{1}{v} = \frac{1}{15} + \frac{1}{10} \\ \frac{1}{v} = \frac{2+3}{30} = \frac{1}{30} \\ v = 30 cm \\ Positive sign indicates that the image is virtual and erect and form \\ 30 cm behind the mirror. \end{array}$

CBSE Important Questions Class 10 Science Chapter 12 – Magnetic Effects of Electric Current

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