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Why is magnetism at the center of a bar magnet zero? 

Magnetic field lines in a bar magnet looks like

Magnetic Field Lines have Direction.png

The magnetic field at the center of the bar magnet is not 0, but weak. 

Infact, magnetic field is minimum at the center

 

Explanation

We know that,

the more magnetic field lines in region, the more magnetic field.

At the center of a bar magnet, magnetic field lines are parallel. So, magnetic field is less there

 

What is an armature? Why is it used?

 

Answer

An armature is a loop of insulated copper wire in the form of a rectangle used in an electric motor.

Function of armature:

An armature enhances the power of the motor and induces motion

 

Why can’t two magnetic field lines ever intersect?

Answer

Please check answer here - Question 3 Page 228

 

Name devices in which permanent magnets are used.

Answer

Devices in which permanent magnets are used 

  • Speakers
  • Headphones
  • Generators
  • Microphones
  • Compass

 

If the number of circular current carrying coils are  (i) doubled (ii) halved, then how will the magnetic field produced by it changed?

 

Answer

We know that,

Magnetic field of a current coil is directly proportional to the number of turns/coils.

 

(a) when number of coils are doubled

Magnetic field of a current coil is directly proportional to the number of turns/coils.

Since number of coils are doubled, magnetic field produced will also double.

 

(b) when number of coils are halved

Magnetic field of a current coil is directly proportional to the number of turns/coils.

Since number of coils are halved, magnetic field produced will also be halved.

 

 

What is the usual current rating of the fuse wire in the line to feed

  1. Lights and fans
  2. Appliances of 2kW or more power

 

Answer

(a) 5A is the usual current rating of the fuse wire in the line to feed lights and fans.

(b) 15A is the usual current rating of the fuse wire in the line to feed appliances of 2kW or more power. 

  1. Class 10
  2. Chapter 13 Class 10 - Magnetic Effects of Electric Current

About the Author

Davneet Singh's photo - Teacher, Computer Engineer, Marketer
Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.