Check sibling questions

PQ is a current carrying conductor in the plane of the paper as shown in the figure below.

Q-1  PQ is a current carrying - Teachoo.jpg

(i) Find the directions of the magnetic fields produced by it at points R and S? 

Given r 1 > r 2 , where will the strength of the magnetic field be larger? Give reasons.

(ii) Field strength are which point will be greater?

(iii) If the polarity of the battery connected to the wire is reversed, how would the direction of the magnetic field be changed?

(iv) Explain the rule that is used to find the direction of the magnetic field for a straight current carrying conductor.

 

Answer:

(i)

Right Hand Thumb rule - Teachoo.jpg

According to right hand thumb rule, the magnetic field lines produced is:

  • Into the plane of the paper in at R
  • Out of it at S

(ii)

Magnetic field strength for a straight current carrying conductor is inversely proportional to the distance from the wire.

So, as distance from the conductor decreases, magnetic field strength increases.

Since r 2 < r 1

  • Magnetic field strength at S will be greater than magnetic field strength at R.

(iii)

Right Hand Thumb Rule When Direction of Current is Reversed - Teachoo.jpg

If the polarity of the battery connected to the wire is reversed, then the direction of current through the conductor is also reversed ie., current will now flow from top to bottom and the direction of magnetic field lines will also be reversed.

 

Now, the magnetic field lines will be:

  • Out of the plane of the paper at R
  • Into the plane of the paper in at S

(iv)

Right Hand Thumb rule is used to find the direction of the magnetic field for a straight current carrying conductor.

 

maxwell-right-hand-thumb-rule---teachoo.png

It states that, if we point the thumb of our right hand in the direction of the current, then the direction in which our fingers curl gives the direction of the magnetic field. 

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CA Maninder Singh is a Chartered Accountant for the past 12 years and a teacher from the past 16 years. He teaches Science, Accounts and English at Teachoo