I'm getting a little confused about which right hand rule to use to find the direction of the magnetic field. There's the right hand slap rule, the right hand screw rule and the right hand rule in which we use the index finger, middle finger and thumb. So can I use any of these three or is there a specific place where they are supposed to be used?

The right hand clasp rule is used to find the direction of magnetic field lines around a conductor. the right hand screw rule is used to find the direction of cross product. But the right hand rule in which we use the three fingers hasnt been used in this entire chapter.

using the right hand screw rule, why did we cross fingers from I to r and not r to I?

Hm...nice qs... it's because the thing coming first in the cross product should be given preference, I mean in I x r, we curl the fingers from I to r, and in r x I, we curl them from r to I, which implies that I x r is not the same as r x I. Hope you get it, and happy learning!😀.

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Course: Class 12 Physics (India) > Unit 4

Lesson 8: Magnetic field on the axis of circular current loop

Magnetic field on the axis of current carrying loop

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Magnetic field on the axis of a circular current loop

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MFCCPart1See video transcript

Value of angle
If $θ$ ‍ is the angle between $\vec{d l}$ ‍ and $\vec{r}$ ‍, what is the value of $s i n (θ)$ ‍?
Choose 1 answer:
(Choice A)
$s i n (θ) = \frac{x}{R}$ ‍
(Choice B)
$s i n (θ) = \frac{R}{r}$ ‍
(Choice C)
$s i n (θ) = 0$ ‍
(Choice D)
$s i n (θ) = 1$ ‍

Angle between $\vec{d l}$ ‍ & $\vec{r}$ ‍

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MFCCpart2 - unlisted videos for KA articlesSee video transcript

Why is the expression for magnetic field, $B = \frac{μ_{0}}{4 π} \frac{I \times 2 π R}{(R^{2} + x^{2})}$ ‍, wrong?

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MFCCPart3 - unlisted for guided articles KASee video transcript

Direction of the field
Identify the correct direction of magnetic field-strength, due to the highlighted $\vec{d l}$ ‍.
Choose 1 answer:
(Choice A)
(Choice B)
(Choice C)
(Choice D)
(Choice E)

Direction of $\vec{d b}$ ‍

Khan Academy video wrapper

MFCCpart4 - unlisted videos for guided KA articlesSee video transcript

Value of cos (alpha)
In the above figure, the expression for $c o s (α)$ ‍ would be
$\cos (α)$ ‍ =
Note 1: Your answer should only contain $x$ ‍ and $R$ ‍.
On desktop:
Press the '/' key to input fractions.
Write 'sqrt' to input square root.
Press the '^' key to input exponents.

Putting it all together

Now that we found the axial component of the magnetic field,

\vec{d b}

, let's find the total field by summing it up over the entire loop. Why don't you give it a shot?

Magnetic field value
The total magnetic field, $B =$ ‍ $\frac{μ_{0}}{2} \times$ ‍
Note: Your input should only have three variables: $I, x,$ ‍ and $R$ ‍
On desktop:
Press the '/' key to input fractions.
Write 'sqrt' to input square root.
Press the '^' key to input exponents.

Khan Academy video wrapper

MFCCPart5 - unlisted videos for kA articleSee video transcript

Bonus! Calculating the field at the center.

To check your understanding, try deriving the magnetic field at the center of the loop from the beginning.
You can also use the above-derived expression to calculate the same (and probably to check your derivation too).

The magnetic field at the center of the loop is
$B_{c}$ ‍ = $\frac{μ_{0}}{2} \times$ ‍
Note: Your input should only have two variables: $I,$ ‍ and $R$ ‍.
On desktop:
Press the '/' key to input fractions.
Write 'sqrt' to input square root.
Press the '^' key to input exponents.

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autumn
Posted 4 years ago. Direct link to autumn's post “I'm getting a little conf...”
I'm getting a little confused about which right hand rule to use to find the direction of the magnetic field. There's the right hand slap rule, the right hand screw rule and the right hand rule in which we use the index finger, middle finger and thumb. So can I use any of these three or is there a specific place where they are supposed to be used?
Button navigates to signup pageComment on autumn's post “I'm getting a little conf...”
(8 votes)
Answer
- Reuben Rengith
  Posted 3 years ago. Direct link to Reuben Rengith's post “The right hand clasp rule...”
  The right hand clasp rule is used to find the direction of magnetic field lines around a conductor.
  the right hand screw rule is used to find the direction of cross product.
  But the right hand rule in which we use the three fingers hasnt been used in this entire chapter.
  Comment on Reuben Rengith's post “The right hand clasp rule...”
  (5 votes)
Kinjal
Posted 3 years ago. Direct link to Kinjal's post “using the right hand scre...”
using the right hand screw rule, why did we cross fingers from I to r and not r to I?
Button navigates to signup pageComment on Kinjal's post “using the right hand scre...”
(3 votes)
Answer
- Shresthi
  Posted 3 years ago. Direct link to Shresthi's post “Hm...nice qs... it's beca...”
  Hm...nice qs... it's because the thing coming first in the cross product should be given preference, I mean in I x r, we curl the fingers from I to r, and in r x I, we curl them from r to I, which implies that I x r is not the same as r x I.
  
  Hope you get it, and happy learning!😀.
  Comment on Shresthi's post “Hm...nice qs... it's beca...”
  (4 votes)

Class 12 Physics (India)

Course: Class 12 Physics (India) > Unit 4

Magnetic field on the axis of a circular current loop

Angle between dl→‍ &r→‍

Direction of db→‍

Bonus! Calculating the field at the center.

Want to join the conversation?

Angle between $\vec{d l}$ ‍ & $\vec{r}$ ‍

Direction of $\vec{d b}$ ‍