A current carrying rectangular loop PQRS is made of uniform wire. The length PR = QS = 5cmandPQ = RS = 100cm . If ammeter current reading changes from I to 2I , the ratio of magnetic forces per unit length on the wire

Correct answer: B. 1: 4 Force acting per unit length between two parallel wires is given by, f = μ _ 0 I _ 1 I _ 2 2 . Clearly, f ∝ I _ 1 I _ 2 Therefore, f _ PQ ^ I : f _ PQ ^ 2I = (I × I)/((2I) × (2I)) = 1: 4

JEE Main 202330 JanuaryEvening Shift

Exam: JEE Main
Year: 2023
Date: 30 January
Shift: Evening Shift
Subject: Physics
Chapter: Magnetic Effects of Current

JEE Main 2023 · 30 January · Evening Shift · Physics · Magnetic Effects of Current

A current carrying rectangular loop PQRS is made of uniform wire....

A current carrying rectangular loop $PQRS$ is made of uniform wire. The length $PR = QS = 5cm\text{and}PQ = RS = 100cm$ . If ammeter current reading changes from $I to 2I$ , the ratio of magnetic forces per unit length on the wire $PQ$ due to wire $RS$ in the two cases respectively $\left({f}_{PQ}^{I}: {f}_{PQ}^{2I}\right)$ is:

A current carrying rectangular loop PQRS is made of uniform wire. The length PR = QS = 5cmandPQ = RS = 100cm . If

Options

A $1: 2$
B $1: 4$
C $1: 5$
D $1: 3$

Correct answer

B. $1: 4$

Step-by-step solution

Force acting per unit length between two parallel wires is given by, $f = \dfrac{{\mu}_{0}{I}_{1}{I}_{2}}{2\pid}$ .

Clearly, $f ∝ {I}_{1}{I}_{2}$

Therefore, ${f}_{PQ}^{I}: {f}_{PQ}^{2I} = \dfrac{I \times I}{\left(2I\right) \times \left(2I\right)} = 1: 4$

Practice Magnetic Effects of Current on Quantrex Academy →

More from Magnetic Effects of Current

A hollow, right circular cone of base radius R and height h , with its tip at the origin… JEE Advanced 2026 In a vacuum chamber, a particle of charge 1\ and mass 1 mg is projected with a velocity (… JEE Advanced 2026 A current carrying circular loop of radius 2 cm with unit normal n = k + i 2 is placed in… JEE Main 2026 A 5 mg particle carrying a charge of 5π× 10^ -6 C is moving with velocity of (3 i +2 k )×… JEE Main 2026 A current of 30 A each flows in opposite directions in two conducting wires, placed… JEE Main 2026 A small cube of side 1 mm is placed at the centre of a circular loop of radius 10 cm… JEE Main 2026 The charged particle moving in a uniform magnetic field of (3 i + 2 j ) T has an… JEE Main 2026 A circular coil of radius 2 cm and 125 turns carries a current of 1 A. The coil is placed… JEE Main 2026 Full Magnetic Effects of Current list All JEE Main PYQs