Physics Quiz on Moving Charges

Assertion: A charge, whether stationary or in motion produces a magnetic field around it. Reason: Moving charges produce only electric field in the surrounding space.

• If both assertion and reason are true and reason is the correct explanation of the assertion.

• If both assertion and reason are true but reason is not correct explanation of the assertion.

• If assertion is true, but reason is false.

• Both assertion and reason are false.

The magnetic field푑퐵 due to a small current element푑푙 at a distance Ԧ푟 and element carrying current 푖 is (1996)

• dB=μ0/4π(i^2)(dℓ×Ԧr)/r

• dB=μ0/4π(i)(dℓ×Ԧr)/r^3

• dB=μ0/4π(i)(dℓ×Ԧr)/r^2

• dB=μ0/4π(i^2)(dℓ×Ԧr)/r

Assertion (A): A current element is a source of magnetic field. Reason (R): A moving charge is a source of magnetic field.

• If both assertion and reason are true and reason is the correct explanation of the assertion.

• If both assertion and reason are true but reason is not correct explanation of the assertion.

• If assertion is true, but reason is false.

• Assertion is false, reason is true

Statement I: Biot-Savart's law gives us the expression for the magnetic field strength of an infinitesimal current element (idl) of a current carrying conductor only. Statement II: Biot-Savart's law is analogous to Coulomb's inverse square law of charge q, with the former being related to the field produced by a vector source, idl while the latter being produced by a scalar source, q.

• Both statement I and II are correct

• Both statement I and II are incorrect

• Statement I is correct and statement II is incorrect

• Statement I is incorrect and statement II is correct

The magnetic induction due to an infinitely long straight wire carrying a current i at a distance r from the wire is given by (PYQ)

• μ0/2π(i/r)

• μ0/4π(i^2/r)

• μ0/4π(i^2/r^2)

• μ0/2π(i^2/r)

The magnetic induction at a point P which is distant 4 cm from a long current carrying wire is 10–8 Tesla. The field of induction at a distance 8 cm from the same current would be: (Similar in 1990, 1992)

• 5 × 10–9 Tesla

• 0.5 × 10–9 Tesla

• 2 × 10–8 Tesla

• 8 × 10–9 Tesla

A straight section PQ of circuit lies along X-axis from x = –a/2 to x = a/2 and carries a steady current i. The magnetic field due to the section PQ at a point X = + a will be

• Proportional to a

• Proportional to a^2

• Proportional to 1/a

• zero

Find the magnetic field at point P due to a straight line segment AB of length 6 cm carrying a current of 5 A (see figure) (μ0 = 4π × 10–7 N-A–2) (JEE Main 2019)

• 3.0 × 10–5 T

• 2.5 × 10–5 T

• 2.0 × 10–5 T

• 1.5 × 10–5 T

The magnetic field at centre, P will be (2000)

• μ0/4π

• μ0/π

• μ0/2π

• 4 μ0/π

Magnetic field due to 0.1 A current flowing through a circular coil of radius 0.1 m and 1000 turns at the centre of the coil is [1999]

• 6.28 × 10–4 T

• 4.31 × 10–2 T

• 2 × 10–1 T

• 9.81 × 10–4 T