NEET Magnetic Effects of Current and Magnetism — Set 10

Question 1

A rectangular loop of area $ 0.03 \, \text{m}^2 $ with 20 turns carries $ 4 \, \text{A} $ in a field of $ 0.9 \, \text{T} $ perpendicular to the plane. What is the torque?

Accepted Answer

$ \tau = N I A B \sin \theta $, $ \theta = 90^\circ $ to plane means $ \sin 0^\circ = 1 $ with normal. $ \tau = 20 \times 4 \times 0.03 \times 0.9 \times 1 = 2.16 \, \text{N m} $.

Question 2

Two parallel wires $ 0.07 \, \text{m} $ apart carry currents of $ 9 \, \text{A} $ and $ 2 \, \text{A} $ in the same direction. What is the force per unit length between them? ($ \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} $)

Accepted Answer

Force per unit length $ f = \frac{\mu_0 I_1 I_2}{2 \pi d} $. $ f = \frac{4 \pi \times 10^{-7} \times 9 \times 2}{2 \pi \times 0.07} = \frac{72 \times 10^{-7}}{0.14} = 5.14 \times 10^{-6} \, \text{N/m} $.

Question 3

Two parallel wires $ 0.12 \, \text{m} $ apart carry $ 7 \, \text{A} $ and $ 3 \, \text{A} $ in the same direction. What is the force per unit length? ($ \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} $)

Accepted Answer

$ f = \frac{\mu_0 I_1 I_2}{2 \pi d} $. $ f = \frac{4 \pi \times 10^{-7} \times 7 \times 3}{2 \pi \times 0.12} = \frac{84 \times 10^{-7}}{0.24} = 3.5 \times 10^{-6} \, \text{N/m} $.

NEET Physics: Magnetic Effects of Current and Magnetism — Practice Set 10

Q1. A rectangular loop of area \( 0.03 \, \text{m}^2 \) with 20 turns carries \( 4 \, \text{A} \) in a field of \( 0.9 \, \text{T} \) perpendicular to the plane. What is the torque?

Q2. Two parallel wires \( 0.07 \, \text{m} \) apart carry currents of \( 9 \, \text{A} \) and \( 2 \, \text{A} \) in the same direction. What is the force per unit length between them? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q3. Two parallel wires \( 0.12 \, \text{m} \) apart carry \( 7 \, \text{A} \) and \( 3 \, \text{A} \) in the same direction. What is the force per unit length? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q4. A solenoid with 1800 turns per meter carries a current of \( 1.5 \, \text{A} \). What is the magnetic field inside it? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q5. Two parallel wires \( 0.06 \, \text{m} \) apart carry \( 7 \, \text{A} \) and \( 5 \, \text{A} \) in the same direction. What is the force per unit length? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q6. A rectangular loop of area \( 0.09 \, \text{m}^2 \) with 18 turns carries \( 2 \, \text{A} \) in a field of \( 0.6 \, \text{T} \) perpendicular to the plane. What is the torque?

Q7. In a moving coil galvanometer, what provides the restoring torque to balance the magnetic torque?

Q8. A proton moves at \( 7.5 \times 10^7 \, \text{m/s} \) perpendicular to a field of \( 0.12 \, \text{T} \). What is the magnetic force? (Charge = \( 1.6 \times 10^{-19} \, \text{C} \))

Q9. A wire of length \( 2.3 \, \text{m} \) carrying \( 4 \, \text{A} \) is at \( 60^\circ \) to a magnetic field of \( 0.6 \, \text{T} \). What is the force on the wire?

Q10. A solenoid with 1300 turns per meter carries \( 1.2 \, \text{A} \). What is the magnetic field inside? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))