NIOS Class 12 Physics Chapter 18 Magnetism and Magnetic Effect of Electric Current

NIOS Class 12 Physics Chapter 18 Magnetism and Magnetic Effect of Electric Current Solutions English Medium As Per New Syllabus to each chapter is provided in the list so that you can easily browse throughout different chapters NIOS Class 12 Physics Chapter 18 Magnetism and Magnetic Effect of Electric Current Notes in English and select need one. NIOS Class 12 Physics Solutions English Medium Download PDF. NIOS Study Material of Class 12 Physics Notes Paper Code: 312.

NIOS Class 12 Physics Chapter 18 Magnetism and Magnetic Effect of Electric Current

Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 12 Physics Notes, NIOS Senior Secondary Course Physics Solutions in English for All Chapter, You can practice these here.

Magnetism and Magnetic Effect of Electric Current

Chapter: 18

Module-V: Electricity and Magnetism

INTEXT QUESTIONS 18.1

1. You are given a magnet. How will you locate its north pole?

Ans: To locate the north pole of a magnet:

(i) Using Earth’s Magnetic Field:

(a) Suspend the magnet freely with a thread tied at its center so it can rotate without friction.

(b) Allow it to come to rest.

(c) The end of the magnet that points towards the geographical north is the north pole of the magnet.

(d) This happens because the Earth behaves like a giant magnet, and unlike poles attract.

(ii) Using a Known Magnet:

(a)  Take another magnet whose poles are already marked.

(b) Bring the north pole of the known magnet near one end of the unknown magnet.

(c) If repulsion occurs, that end is the north pole.

(d) If attraction occurs, that end is the south pole.

2. You are provided two identical looking iron bars. One of these is a magnet. Using just these two, how will you identify which of the two is a magnet?

Ans: To identify which bar is the magnet:

(i) Method:

• Take bar A and bring it near the middle (center) of bar B

• middle (center) of bar A

• Observe the behavior in both cases

Reasoning:

A magnet has poles only at its ends; the middle has no magnetic strength

An iron bar gets magnetized by induction when a magnet approaches it

If bar A is the magnet:

When A approaches middle of B: Attraction occurs (A magnetizes B)

When B approaches middle of A: No attraction (middle of magnet has no poles)

Conclusion:

The bar that shows attraction when brought near the middle of the other bar is the magnet.

3. You are given a thread and two bar magnets. Describe a method by which you can identify the polarities of the two magnets.

Ans: To identify the polarities of both magnets:

(i) Identifying the North Pole of the First Magnet.

(ii) Suspend magnet 1 using the thread at its center of mass.

(iii) Allow it to come to rest freely.

(iv) The end pointing towards geographical north is the north pole of magnet 1.

(v) Mark this end as N₁ and the other as S₁

(vi) Identify Polarities of Second Magnet.

(vii) Take the identified north pole (N₁) of magnet 1

(viii) Bring N₁ near one end of magnet 2

(ix) If repulsion occurs: That end of magnet 2 is also north pole.

(x) If attraction occurs: That end of magnet 2 is south pole.

(xi) The opposite end will have the opposite polarity.

(xi) Principle: Like poles repel each other.

(xiii) Unlike poles attract each other.

Suspend first magnet to find its north pole using Earth’s field, then use it to test the second magnet – repulsion indicates like poles, attraction indicates unlike poles.

INTEXT QUESTIONS 18.2

1. What can you say about the field developed by (i) a stationary electron? (ii) a moving electron?

Ans: (i) Stationary Electron:

• A stationary electron has only electric field around it.

• No magnetic field is produced by a stationary charge.

• The electric field is radial, pointing inward toward the electron (since electron has negative charge).

• Field strength: E = (1/4πε₀) × (e/r²)

(ii) Moving Electron:

• A moving electron produces both electric and magnetic fields.

• Electric field: Still exists due to the charge.

• Magnetic field: Created due to the motion of charge (constitutes current).

• The magnetic field lines are circular around the path of motion.

• Direction follows right-hand rule (but remember electron has negative charge).

(iii) Physical Principle:

• Stationary charges produce only electric fields.

• Moving charges (currents) produce both electric and magnetic fields.

2. Electrons in a conductor are in constant motion due to thermal energy. Why do they not show magnetism till such time that a potential difference is applied across it?

Ans: Although electrons in a conductor are always in thermal motion, they do not produce magnetism because:

Without a potential difference:

• Electrons move randomly in all directions due to thermal energy.
  
• Their motions cancel each other because there is no net flow of electrons in any one direction.
  
• So, the magnetic fields produced by individual electrons also cancel out.
  
• Therefore, the net magnetic field is zero.
  

When a potential difference is applied:

• An external electric field is created inside the conductor.
  
• Electrons now gain a small drift velocity in a definite direction.
  
• A net current flows through the conductor.
  
• All moving electrons then produce magnetic fields in the same direction.
  
• Hence, a net magnetic field is produced.