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The magnetic flux near the axis and in...

The magnetic flux near the axis and inside the air core solenoid of length `60 cm` carrying current 'f' is `1.57 xx 10^(-6) Wb`. Its magnetic moment will be (cross-sectional area of a solenoid is very small as compared to its length.
`mu_(0)= 4pi xx 10^(-7) `SI unit )

A

`0.25Am^2`

B

`0.5Am^2`

C

`0.75Am^2`

D

`1Am^2`

Text Solution

AI Generated Solution

The correct Answer is:
To find the magnetic moment of the solenoid based on the given magnetic flux, we can follow these steps: ### Step 1: Understand the relationship between magnetic flux, magnetic field, and area. The magnetic flux (Φ) through a surface is given by the formula: \[ \Phi = B \cdot A \cdot \cos(\theta) \] Where: - \(B\) is the magnetic field, - \(A\) is the area, - \(\theta\) is the angle between the magnetic field and the normal to the surface. Since the magnetic field and the area vector are parallel in this case, \(\theta = 0\) degrees, and thus \(\cos(0) = 1\). So, we can simplify the equation to: \[ \Phi = B \cdot A \] ### Step 2: Determine the magnetic field inside the solenoid. The magnetic field inside a long solenoid is given by: \[ B = \mu_0 \cdot n \cdot I \] Where: - \(\mu_0 = 4\pi \times 10^{-7} \, \text{T m/A}\) (permeability of free space), - \(n\) is the number of turns per unit length, - \(I\) is the current flowing through the solenoid. ### Step 3: Relate magnetic moment to magnetic flux. The magnetic moment (\(m\)) of the solenoid can be expressed as: \[ m = n \cdot I \cdot A \] Where \(A\) is the cross-sectional area of the solenoid. ### Step 4: Set up the relationship between magnetic flux and magnetic moment. From the equations for flux and magnetic moment, we can relate them: \[ \Phi = B \cdot A = \mu_0 \cdot n \cdot I \cdot A \] Dividing both sides by \(A\): \[ \frac{\Phi}{A} = \mu_0 \cdot n \cdot I \] Now, we can express \(n\) in terms of the length \(L\) of the solenoid: \[ n = \frac{N}{L} \] Where \(N\) is the total number of turns. ### Step 5: Substitute \(n\) into the magnetic moment equation. We can express the magnetic moment in terms of the flux: \[ m = \frac{\Phi \cdot L}{\mu_0} \] ### Step 6: Substitute the values into the equation. Given: - \(\Phi = 1.57 \times 10^{-6} \, \text{Wb}\) - \(L = 60 \, \text{cm} = 0.6 \, \text{m}\) - \(\mu_0 = 4\pi \times 10^{-7} \, \text{T m/A}\) Now substitute these values into the equation for magnetic moment: \[ m = \frac{1.57 \times 10^{-6} \cdot 0.6}{4\pi \times 10^{-7}} \] ### Step 7: Calculate the magnetic moment. Calculating the above expression: \[ m = \frac{1.57 \times 10^{-6} \cdot 0.6}{4\pi \times 10^{-7}} \approx \frac{9.42 \times 10^{-7}}{1.25664 \times 10^{-6}} \approx 0.75 \, \text{A m}^2 \] ### Final Answer: The magnetic moment \(m\) is approximately \(0.75 \, \text{A m}^2\). ---
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