NEET Magnetic Effects of Current and Magnetism — Set 12

Question 1

A rectangular loop of area $ 0.02 \, \text{m}^2 $ with 10 turns carries $ 3 \, \text{A} $ in a field of $ 0.5 \, \text{T} $ at $ 60^\circ $ to the plane. What is the torque?

Accepted Answer

$ \tau = N I A B \sin \theta $, where $ \theta = 60^\circ $ to the plane means $ \sin 30^\circ $ with the normal. $ \tau = 10 \times 3 \times 0.02 \times 0.5 \times \sin 60^\circ = 0.3 \times 0.866 = 0.2598 \approx 0.26 \, \text{N m} $.

Question 2

An electron moves at $ 5 \times 10^6 \, \text{m/s} $ perpendicular to a magnetic field of $ 0.2 \, \text{T} $. What is the magnetic force on it? (Charge of electron = $ 1.6 \times 10^{-19} \, \text{C} $)

Accepted Answer

Force $ F = q v B \sin \theta $, $ \theta = 90^\circ $, so $ \sin \theta = 1 $. $ F = 1.6 \times 10^{-19} \times 5 \times 10^6 \times 0.2 = 1.6 \times 10^{-13} \, \text{N} $.

Question 3

A straight wire of length $ 1.2 \, \text{m} $ carries a current of $ 6 \, \text{A} $ perpendicular to a uniform magnetic field of $ 0.25 \, \text{T} $. What is the force acting on the wire?

Accepted Answer

Force $ F = I l B \sin \theta $, where $ \theta = 90^\circ $, so $ \sin \theta = 1 $. $ F = 6 \times 1.2 \times 0.25 = 1.8 \, \text{N} $.

NEET Physics: Magnetic Effects of Current and Magnetism — Practice Set 12

Q1. A rectangular loop of area \( 0.02 \, \text{m}^2 \) with 10 turns carries \( 3 \, \text{A} \) in a field of \( 0.5 \, \text{T} \) at \( 60^\circ \) to the plane. What is the torque?

Q2. An electron moves at \( 5 \times 10^6 \, \text{m/s} \) perpendicular to a magnetic field of \( 0.2 \, \text{T} \). What is the magnetic force on it? (Charge of electron = \( 1.6 \times 10^{-19} \, \text{C} \))

Q3. A straight wire of length \( 1.2 \, \text{m} \) carries a current of \( 6 \, \text{A} \) perpendicular to a uniform magnetic field of \( 0.25 \, \text{T} \). What is the force acting on the wire?

Q4. A square loop of side \( 0.25 \, \text{m} \) with 20 turns carries \( 2.5 \, \text{A} \) in a magnetic field of \( 0.3 \, \text{T} \). The plane of the loop is at \( 45^\circ \) to the field. What is the torque?

Q5. A solenoid has 850 turns per meter and carries a current of \( 1.6 \, \text{A} \). What is the magnetic field inside it? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q6. Two parallel wires \( 0.1 \, \text{m} \) apart carry \( 8 \, \text{A} \) and \( 6 \, \text{A} \) in the same direction. What is the force per unit length? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q7. A proton moves at \( 4 \times 10^7 \, \text{m/s} \) perpendicular to a field of \( 0.05 \, \text{T} \). What is the radius of its path? (Mass = \( 1.67 \times 10^{-27} \, \text{kg} \), charge = \( 1.6 \times 10^{-19} \, \text{C} \))

Q8. A square loop of side \( 0.12 \, \text{m} \) with 35 turns carries \( 1.8 \, \text{A} \) in a magnetic field of \( 0.5 \, \text{T} \). The plane of the loop is at \( 30^\circ \) to the field. What is the torque?

Q9. Two parallel wires \( 0.01 \, \text{m} \) apart carry \( 5 \, \text{A} \) and \( 6 \, \text{A} \) in opposite directions. What is the force per unit length? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q10. What is the condition for zero torque on a current-carrying loop in a magnetic field?