CBSE 2025 · Region 5 · Set 2 · Q27 · 3 marks
(a)Use Ampere's law to derive the expression for the magnetic field due to a long straight current carrying wire of infinite length.(b)Why is Ampere's law used for the derivation in (a) above and not Biot-Savart's law? Explain.
(a)
Use Ampere's law to derive the expression for the magnetic field due to a long straight current carrying wire of infinite length.
(b)
Why is Ampere's law used for the derivation in (a) above and not Biot-Savart's law? Explain.
Marking-scheme solution
(a)
Consider an Amperian loop of radius R around the wire carrying current I.
$\displaystyle \oint \vec{B} \cdot d \vec{l}=\mu_{0} i$
$\displaystyle B \times 2 \pi r=\mu_{0} i$
$\displaystyle B=\frac{\mu_{0} i}{2 \pi r}$
(b)
The expression for the magnetic field due to a long straight current carrying infinite wire can be obtained easily using Ampere's circuital law, whereas Biot-Savart's law requires lengthy calculation.
Moving Charges and MagnetismAmpere’s Circuital LawApplyshort_answermedium
More from Moving Charges and Magnetism
- A 2.0 cm segment of wire, carrying 5.0 A current in positive y-direction lies along y -axis, as shown in the…2024 · asked 3×
- Derive an expression for the magnetic field B, due to a circular coil of N turns, each of radius r carrying…2026 · asked 3×
- Assertion: A proton and an electron enter a uniform magnetic field B with the same momentum p such that p is…2024 · asked 3×
- (i) A particle of mass m and charge q is moving with a velocity v in a magnetic field B as shown in the…2024 · asked 3×
- Figure shows a narrow beam of electrons entering with a velocity of 3 × 10^7 m / s, symmetrically through the…2026 · asked 3×
- A 1 cm straight segment of a conductor carrying 1 A current in x direction lies symmetrically at origin of…2025 · asked 3×
- A rectangular loop carries a current of 1 A. A straight long wire carrying 2 A current is kept near the loop…2025 · asked 3×
- Assertion: Two long parallel wires, freely suspended and connected in series to a battery, move apart. Reason…2024 · asked 3×
CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.